[PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Marek Szyprowski]

Scatterlist elements contains both pages and DMA addresses, but in general,
one cannot assume 1:1 relation between them. The sg->length is the size of
the physical memory chunk described by sg->page, while sg_dma_length(sg) is
the size of the DMA (IO virtual) chunk described by sg_dma_address(sg).

The proper way of extracting both: pages and DMA addresses of the whole
buffer described by a scatterlist it to iterate independently over the
sg->pages/sg->length and sg_dma_address(sg)/sg_dma_len(sg) entries.

Fixes: 42e67b479eab ("drm/prime: use dma length macro when mapping sg")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
This fixes the following kernel panic observed on ARM 32bit Samsung
Exynos5250-based Snow Chromebook since linux-next 20200326, which
introduced the commit 42e67b479eab ("drm/prime: use dma length macro when
mapping sg"):

 [drm] Initialized panfrost 1.1.0 20180908 for 11800000.gpu on minor 0
 [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
 exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
 exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
 exynos-drm exynos-drm: bound 145b0000.dp-controller (ops exynos_dp_ops)
 exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops)
 [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 12 at mm/vmalloc.c:163 vmap_page_range_noflush+0x18c/0x1b0
 Modules linked in:
 CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
 Hardware name: Samsung Exynos (Flattened Device Tree)
 Workqueue: events deferred_probe_work_func
 [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
 [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
 [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
 [<c01271a0>] (__warn) from [<c0127268>] (warn_slowpath_fmt+0xb0/0xb8)
 [<c0127268>] (warn_slowpath_fmt) from [<c0294fdc>] (vmap_page_range_noflush+0x18c/0x1b0)
 [<c0294fdc>] (vmap_page_range_noflush) from [<c02952fc>] (map_vm_area+0x30/0x6c)
 [<c02952fc>] (map_vm_area) from [<c0298df8>] (vmap+0x64/0x80)
 [<c0298df8>] (vmap) from [<c05f71f4>] (exynos_drm_fbdev_create+0x148/0x270)
 [<c05f71f4>] (exynos_drm_fbdev_create) from [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock+0x388/0x5dc)
 [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock) from [<c05f743c>] (exynos_drm_fbdev_init+0x78/0xe0)
 [<c05f743c>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
 [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
 [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
 [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
 [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
 [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
 [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
 [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
 [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
 [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
 [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
 [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
 [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
 [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
 [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
 Exception stack(0xee8fdfb0 to 0xee8fdff8)
 dfa0:                                     00000000 00000000 00000000 00000000
 dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
 irq event stamp: 54037
 hardirqs last  enabled at (54055): [<c019ed50>] console_unlock+0x58c/0x6a8
 hardirqs last disabled at (54062): [<c019e890>] console_unlock+0xcc/0x6a8
 softirqs last  enabled at (54078): [<c0101724>] __do_softirq+0x4fc/0x5f4
 softirqs last disabled at (54089): [<c0130248>] irq_exit+0x16c/0x170
 ---[ end trace 74519922e0e4625d ]---
 exynos4-fb 14400000.fimd: [drm:exynos_drm_fbdev_create] *ERROR* failed to map pages to kernel space.
 exynos-drm exynos-drm: [drm:exynos_drm_fbdev_init] *ERROR* failed to set up hw configuration.
 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 12 at kernel/locking/mutex-debug.c:103 mutex_destroy+0x84/0x88
 DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock))
 Modules linked in:
 CPU: 0 PID: 12 Comm: kworker/0:1 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
 Hardware name: Samsung Exynos (Flattened Device Tree)
 Workqueue: events deferred_probe_work_func
 [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
 [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
 [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
 [<c01271a0>] (__warn) from [<c012722c>] (warn_slowpath_fmt+0x74/0xb8)
 [<c012722c>] (warn_slowpath_fmt) from [<c01892a4>] (mutex_destroy+0x84/0x88)
 [<c01892a4>] (mutex_destroy) from [<c05be1a4>] (drm_fb_helper_fini.part.1+0x9c/0xd4)
 [<c05be1a4>] (drm_fb_helper_fini.part.1) from [<c05f7464>] (exynos_drm_fbdev_init+0xa0/0xe0)
 [<c05f7464>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
 [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
 [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
 [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
 [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
 [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
 [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
 [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
 [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
 [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
 [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
 [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
 [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
 [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
 [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
 Exception stack(0xee8fdfb0 to 0xee8fdff8)
 dfa0:                                     00000000 00000000 00000000 00000000
 dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
 irq event stamp: 56283
 hardirqs last  enabled at (56283): [<c02b189c>] kfree+0x198/0x3e4
 hardirqs last disabled at (56282): [<c02b17d0>] kfree+0xcc/0x3e4
 softirqs last  enabled at (56262): [<c0101724>] __do_softirq+0x4fc/0x5f4
 softirqs last disabled at (56255): [<c0130248>] irq_exit+0x16c/0x170
 ---[ end trace 74519922e0e4625e ]---
 exynos-sysmmu 14640000.sysmmu: 14400000.fimd: PAGE FAULT occurred at 0x20000000
 ------------[ cut here ]------------
 kernel BUG at drivers/iommu/exynos-iommu.c:447!
 Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
 Modules linked in:
 CPU: 0 PID: 52 Comm: kworker/0:2 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
 Hardware name: Samsung Exynos (Flattened Device Tree)
 Workqueue: events output_poll_execute
 PC is at exynos_sysmmu_irq+0x210/0x258
 LR is at report_iommu_fault+0x144/0x1cc
 pc : [<c05a6e34>]    lr : [<c05a13ec>]    psr: a0000193
 sp : cfafdbe8  ip : 2d495ebb  fp : 00000200
 r10: eeb187e0  r9 : 20000000  r8 : cf300000
 r7 : c11d4fb0  r6 : eeb187c0  r5 : 00000000  r4 : c0b59f74
 r3 : cfafc000  r2 : 00010001  r1 : 00000000  r0 : ffffffda
 Flags: NzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
 Control: 10c5387d  Table: 4000406a  DAC: 00000051
 Process kworker/0:2 (pid: 52, stack limit = 0x(ptrval))
 Stack: (0xcfafdbe8 to 0xcfafe000)
 ...
 [<c05a6e34>] (exynos_sysmmu_irq) from [<c01a24f4>] (__handle_irq_event_percpu+0x68/0x42c)
 [<c01a24f4>] (__handle_irq_event_percpu) from [<c01a28e4>] (handle_irq_event_percpu+0x2c/0x7c)
 [<c01a28e4>] (handle_irq_event_percpu) from [<c01a296c>] (handle_irq_event+0x38/0x5c)
 [<c01a296c>] (handle_irq_event) from [<c01a7160>] (handle_level_irq+0xcc/0x150)
 [<c01a7160>] (handle_level_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
 [<c01a1574>] (generic_handle_irq) from [<c0509a5c>] (combiner_handle_cascade_irq+0x8c/0xdc)
 [<c0509a5c>] (combiner_handle_cascade_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
 [<c01a1574>] (generic_handle_irq) from [<c01a1bbc>] (__handle_domain_irq+0x7c/0xec)
 [<c01a1bbc>] (__handle_domain_irq) from [<c050a024>] (gic_handle_irq+0x58/0x9c)
 [<c050a024>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
 Exception stack(0xcfafdd00 to 0xcfafdd48)
 dd00: c02b189c 00000000 2df3c000 00000000 cf2ed3c0 ee801cc0 60000113 ef1ddda0
 dd20: c05d5500 00000000 cf2c9800 cf2ea8b8 00003220 cfafdd50 c02b189c c02b18a0
 dd40: 60000113 ffffffff
 [<c0100af0>] (__irq_svc) from [<c02b18a0>] (kfree+0x19c/0x3e4)
 [<c02b18a0>] (kfree) from [<c05d5500>] (drm_atomic_state_default_clear+0x1b8/0x2dc)
 [<c05d5500>] (drm_atomic_state_default_clear) from [<c05d5650>] (__drm_atomic_state_free+0x10/0x50)
 [<c05d5650>] (__drm_atomic_state_free) from [<c05e9d88>] (drm_client_modeset_commit_atomic+0x240/0x26c)
 [<c05e9d88>] (drm_client_modeset_commit_atomic) from [<c05e9df8>] (drm_client_modeset_commit_locked+0x44/0x1d0)
 [<c05e9df8>] (drm_client_modeset_commit_locked) from [<c05e9fa8>] (drm_client_modeset_commit+0x24/0x40)
 [<c05e9fa8>] (drm_client_modeset_commit) from [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked+0x58/0xa4)
 [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked) from [<c05be468>] (drm_fb_helper_set_par+0x30/0x5c)
 [<c05be468>] (drm_fb_helper_set_par) from [<c05be538>] (drm_fb_helper_hotplug_event.part.5+0xa4/0xbc)
 [<c05be538>] (drm_fb_helper_hotplug_event.part.5) from [<c05ac148>] (drm_kms_helper_hotplug_event+0x24/0x30)
 [<c05ac148>] (drm_kms_helper_hotplug_event) from [<c05ac238>] (output_poll_execute+0xb8/0x1b4)
 [<c05ac238>] (output_poll_execute) from [<c0149f9c>] (process_one_work+0x30c/0x880)
 [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
 [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
 [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
 Exception stack(0xcfafdfb0 to 0xcfafdff8)
 dfa0:                                     00000000 00000000 00000000 00000000
 dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
 Code: e34c00de e300119e ebee00e1 eaffff81 (e7f001f2) 
 ---[ end trace 74519922e0e4625f ]---
 Kernel panic - not syncing: Fatal exception in interrupt
 CPU1: stopping
 CPU: 1 PID: 0 Comm: swapper/1 Tainted: G      D W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
 Hardware name: Samsung Exynos (Flattened Device Tree)
 [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
 [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
 [<c0a78178>] (dump_stack) from [<c0110ad4>] (handle_IPI+0x3b4/0x440)
 [<c0110ad4>] (handle_IPI) from [<c050a064>] (gic_handle_irq+0x98/0x9c)
 [<c050a064>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
 Exception stack(0xee8fff58 to 0xee8fffa0)
 ff40:                                                       c0109534 00000000
 ff60: 2df50000 00000000 ee8fe000 c1108ee8 c1108f2c 00000002 00000000 c0de63c0
 ff80: 00000000 c1075fe8 2d495ebb ee8fffa8 c0109534 c0109538 60000013 ffffffff
 [<c0100af0>] (__irq_svc) from [<c0109538>] (arch_cpu_idle+0x24/0x44)
 [<c0109538>] (arch_cpu_idle) from [<c0163a74>] (do_idle+0x1d8/0x2d4)
 [<c0163a74>] (do_idle) from [<c0163f24>] (cpu_startup_entry+0x18/0x1c)
 [<c0163f24>] (cpu_startup_entry) from [<401018ac>] (0x401018ac)
 ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
---
 drivers/gpu/drm/drm_prime.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 1de2cde2277c..424db18987f6 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -962,27 +962,33 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
 	unsigned count;
 	struct scatterlist *sg;
 	struct page *page;
-	u32 len, index;
+	u32 page_len, page_index;
 	dma_addr_t addr;
+	u32 dma_len, dma_index;
 
-	index = 0;
+	page_index = 0;
+	dma_index = 0;
 	for_each_sg(sgt->sgl, sg, sgt->nents, count) {
-		len = sg_dma_len(sg);
+		page_len = sg->length;
 		page = sg_page(sg);
+		dma_len = sg_dma_len(sg);
 		addr = sg_dma_address(sg);
 
-		while (len > 0) {
-			if (WARN_ON(index >= max_entries))
+		while (pages && page_len > 0) {
+			if (WARN_ON(page_index >= max_entries))
 				return -1;
-			if (pages)
-				pages[index] = page;
-			if (addrs)
-				addrs[index] = addr;
-
+			pages[page_index] = page;
 			page++;
+			page_len -= PAGE_SIZE;
+			page_index++;
+		}
+		while (addrs && dma_len > 0) {
+			if (WARN_ON(dma_index >= max_entries))
+				return -1;
+			addrs[dma_index] = addr;
 			addr += PAGE_SIZE;
-			len -= PAGE_SIZE;
-			index++;
+			dma_len -= PAGE_SIZE;
+			dma_index++;
 		}
 	}
 	return 0;
-- 
2.17.1

[PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Marek Szyprowski]

Scatterlist elements contains both pages and DMA addresses, but in general,
one cannot assume 1:1 relation between them. The sg->length is the size of
the physical memory chunk described by sg->page, while sg_dma_length(sg) is
the size of the DMA (IO virtual) chunk described by sg_dma_address(sg).

The proper way of extracting both: pages and DMA addresses of the whole
buffer described by a scatterlist it to iterate independently over the
sg->pages/sg->length and sg_dma_address(sg)/sg_dma_len(sg) entries.

Fixes: 42e67b479eab ("drm/prime: use dma length macro when mapping sg")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
---
This fixes the following kernel panic observed on ARM 32bit Samsung
Exynos5250-based Snow Chromebook since linux-next 20200326, which
introduced the commit 42e67b479eab ("drm/prime: use dma length macro when
mapping sg"):

 [drm] Initialized panfrost 1.1.0 20180908 for 11800000.gpu on minor 0
 [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
 exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
 exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
 exynos-drm exynos-drm: bound 145b0000.dp-controller (ops exynos_dp_ops)
 exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops)
 [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 12 at mm/vmalloc.c:163 vmap_page_range_noflush+0x18c/0x1b0
 Modules linked in:
 CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
 Hardware name: Samsung Exynos (Flattened Device Tree)
 Workqueue: events deferred_probe_work_func
 [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
 [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
 [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
 [<c01271a0>] (__warn) from [<c0127268>] (warn_slowpath_fmt+0xb0/0xb8)
 [<c0127268>] (warn_slowpath_fmt) from [<c0294fdc>] (vmap_page_range_noflush+0x18c/0x1b0)
 [<c0294fdc>] (vmap_page_range_noflush) from [<c02952fc>] (map_vm_area+0x30/0x6c)
 [<c02952fc>] (map_vm_area) from [<c0298df8>] (vmap+0x64/0x80)
 [<c0298df8>] (vmap) from [<c05f71f4>] (exynos_drm_fbdev_create+0x148/0x270)
 [<c05f71f4>] (exynos_drm_fbdev_create) from [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock+0x388/0x5dc)
 [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock) from [<c05f743c>] (exynos_drm_fbdev_init+0x78/0xe0)
 [<c05f743c>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
 [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
 [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
 [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
 [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
 [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
 [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
 [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
 [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
 [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
 [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
 [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
 [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
 [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
 [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
 Exception stack(0xee8fdfb0 to 0xee8fdff8)
 dfa0:                                     00000000 00000000 00000000 00000000
 dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
 irq event stamp: 54037
 hardirqs last  enabled at (54055): [<c019ed50>] console_unlock+0x58c/0x6a8
 hardirqs last disabled at (54062): [<c019e890>] console_unlock+0xcc/0x6a8
 softirqs last  enabled at (54078): [<c0101724>] __do_softirq+0x4fc/0x5f4
 softirqs last disabled at (54089): [<c0130248>] irq_exit+0x16c/0x170
 ---[ end trace 74519922e0e4625d ]---
 exynos4-fb 14400000.fimd: [drm:exynos_drm_fbdev_create] *ERROR* failed to map pages to kernel space.
 exynos-drm exynos-drm: [drm:exynos_drm_fbdev_init] *ERROR* failed to set up hw configuration.
 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 12 at kernel/locking/mutex-debug.c:103 mutex_destroy+0x84/0x88
 DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock))
 Modules linked in:
 CPU: 0 PID: 12 Comm: kworker/0:1 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
 Hardware name: Samsung Exynos (Flattened Device Tree)
 Workqueue: events deferred_probe_work_func
 [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
 [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
 [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
 [<c01271a0>] (__warn) from [<c012722c>] (warn_slowpath_fmt+0x74/0xb8)
 [<c012722c>] (warn_slowpath_fmt) from [<c01892a4>] (mutex_destroy+0x84/0x88)
 [<c01892a4>] (mutex_destroy) from [<c05be1a4>] (drm_fb_helper_fini.part.1+0x9c/0xd4)
 [<c05be1a4>] (drm_fb_helper_fini.part.1) from [<c05f7464>] (exynos_drm_fbdev_init+0xa0/0xe0)
 [<c05f7464>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
 [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
 [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
 [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
 [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
 [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
 [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
 [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
 [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
 [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
 [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
 [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
 [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
 [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
 [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
 Exception stack(0xee8fdfb0 to 0xee8fdff8)
 dfa0:                                     00000000 00000000 00000000 00000000
 dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
 irq event stamp: 56283
 hardirqs last  enabled at (56283): [<c02b189c>] kfree+0x198/0x3e4
 hardirqs last disabled at (56282): [<c02b17d0>] kfree+0xcc/0x3e4
 softirqs last  enabled at (56262): [<c0101724>] __do_softirq+0x4fc/0x5f4
 softirqs last disabled at (56255): [<c0130248>] irq_exit+0x16c/0x170
 ---[ end trace 74519922e0e4625e ]---
 exynos-sysmmu 14640000.sysmmu: 14400000.fimd: PAGE FAULT occurred at 0x20000000
 ------------[ cut here ]------------
 kernel BUG at drivers/iommu/exynos-iommu.c:447!
 Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
 Modules linked in:
 CPU: 0 PID: 52 Comm: kworker/0:2 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
 Hardware name: Samsung Exynos (Flattened Device Tree)
 Workqueue: events output_poll_execute
 PC is at exynos_sysmmu_irq+0x210/0x258
 LR is at report_iommu_fault+0x144/0x1cc
 pc : [<c05a6e34>]    lr : [<c05a13ec>]    psr: a0000193
 sp : cfafdbe8  ip : 2d495ebb  fp : 00000200
 r10: eeb187e0  r9 : 20000000  r8 : cf300000
 r7 : c11d4fb0  r6 : eeb187c0  r5 : 00000000  r4 : c0b59f74
 r3 : cfafc000  r2 : 00010001  r1 : 00000000  r0 : ffffffda
 Flags: NzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
 Control: 10c5387d  Table: 4000406a  DAC: 00000051
 Process kworker/0:2 (pid: 52, stack limit = 0x(ptrval))
 Stack: (0xcfafdbe8 to 0xcfafe000)
 ...
 [<c05a6e34>] (exynos_sysmmu_irq) from [<c01a24f4>] (__handle_irq_event_percpu+0x68/0x42c)
 [<c01a24f4>] (__handle_irq_event_percpu) from [<c01a28e4>] (handle_irq_event_percpu+0x2c/0x7c)
 [<c01a28e4>] (handle_irq_event_percpu) from [<c01a296c>] (handle_irq_event+0x38/0x5c)
 [<c01a296c>] (handle_irq_event) from [<c01a7160>] (handle_level_irq+0xcc/0x150)
 [<c01a7160>] (handle_level_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
 [<c01a1574>] (generic_handle_irq) from [<c0509a5c>] (combiner_handle_cascade_irq+0x8c/0xdc)
 [<c0509a5c>] (combiner_handle_cascade_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
 [<c01a1574>] (generic_handle_irq) from [<c01a1bbc>] (__handle_domain_irq+0x7c/0xec)
 [<c01a1bbc>] (__handle_domain_irq) from [<c050a024>] (gic_handle_irq+0x58/0x9c)
 [<c050a024>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
 Exception stack(0xcfafdd00 to 0xcfafdd48)
 dd00: c02b189c 00000000 2df3c000 00000000 cf2ed3c0 ee801cc0 60000113 ef1ddda0
 dd20: c05d5500 00000000 cf2c9800 cf2ea8b8 00003220 cfafdd50 c02b189c c02b18a0
 dd40: 60000113 ffffffff
 [<c0100af0>] (__irq_svc) from [<c02b18a0>] (kfree+0x19c/0x3e4)
 [<c02b18a0>] (kfree) from [<c05d5500>] (drm_atomic_state_default_clear+0x1b8/0x2dc)
 [<c05d5500>] (drm_atomic_state_default_clear) from [<c05d5650>] (__drm_atomic_state_free+0x10/0x50)
 [<c05d5650>] (__drm_atomic_state_free) from [<c05e9d88>] (drm_client_modeset_commit_atomic+0x240/0x26c)
 [<c05e9d88>] (drm_client_modeset_commit_atomic) from [<c05e9df8>] (drm_client_modeset_commit_locked+0x44/0x1d0)
 [<c05e9df8>] (drm_client_modeset_commit_locked) from [<c05e9fa8>] (drm_client_modeset_commit+0x24/0x40)
 [<c05e9fa8>] (drm_client_modeset_commit) from [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked+0x58/0xa4)
 [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked) from [<c05be468>] (drm_fb_helper_set_par+0x30/0x5c)
 [<c05be468>] (drm_fb_helper_set_par) from [<c05be538>] (drm_fb_helper_hotplug_event.part.5+0xa4/0xbc)
 [<c05be538>] (drm_fb_helper_hotplug_event.part.5) from [<c05ac148>] (drm_kms_helper_hotplug_event+0x24/0x30)
 [<c05ac148>] (drm_kms_helper_hotplug_event) from [<c05ac238>] (output_poll_execute+0xb8/0x1b4)
 [<c05ac238>] (output_poll_execute) from [<c0149f9c>] (process_one_work+0x30c/0x880)
 [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
 [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
 [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
 Exception stack(0xcfafdfb0 to 0xcfafdff8)
 dfa0:                                     00000000 00000000 00000000 00000000
 dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
 dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
 Code: e34c00de e300119e ebee00e1 eaffff81 (e7f001f2) 
 ---[ end trace 74519922e0e4625f ]---
 Kernel panic - not syncing: Fatal exception in interrupt
 CPU1: stopping
 CPU: 1 PID: 0 Comm: swapper/1 Tainted: G      D W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
 Hardware name: Samsung Exynos (Flattened Device Tree)
 [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
 [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
 [<c0a78178>] (dump_stack) from [<c0110ad4>] (handle_IPI+0x3b4/0x440)
 [<c0110ad4>] (handle_IPI) from [<c050a064>] (gic_handle_irq+0x98/0x9c)
 [<c050a064>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
 Exception stack(0xee8fff58 to 0xee8fffa0)
 ff40:                                                       c0109534 00000000
 ff60: 2df50000 00000000 ee8fe000 c1108ee8 c1108f2c 00000002 00000000 c0de63c0
 ff80: 00000000 c1075fe8 2d495ebb ee8fffa8 c0109534 c0109538 60000013 ffffffff
 [<c0100af0>] (__irq_svc) from [<c0109538>] (arch_cpu_idle+0x24/0x44)
 [<c0109538>] (arch_cpu_idle) from [<c0163a74>] (do_idle+0x1d8/0x2d4)
 [<c0163a74>] (do_idle) from [<c0163f24>] (cpu_startup_entry+0x18/0x1c)
 [<c0163f24>] (cpu_startup_entry) from [<401018ac>] (0x401018ac)
 ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
---
 drivers/gpu/drm/drm_prime.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 1de2cde2277c..424db18987f6 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -962,27 +962,33 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
 	unsigned count;
 	struct scatterlist *sg;
 	struct page *page;
-	u32 len, index;
+	u32 page_len, page_index;
 	dma_addr_t addr;
+	u32 dma_len, dma_index;
 
-	index = 0;
+	page_index = 0;
+	dma_index = 0;
 	for_each_sg(sgt->sgl, sg, sgt->nents, count) {
-		len = sg_dma_len(sg);
+		page_len = sg->length;
 		page = sg_page(sg);
+		dma_len = sg_dma_len(sg);
 		addr = sg_dma_address(sg);
 
-		while (len > 0) {
-			if (WARN_ON(index >= max_entries))
+		while (pages && page_len > 0) {
+			if (WARN_ON(page_index >= max_entries))
 				return -1;
-			if (pages)
-				pages[index] = page;
-			if (addrs)
-				addrs[index] = addr;
-
+			pages[page_index] = page;
 			page++;
+			page_len -= PAGE_SIZE;
+			page_index++;
+		}
+		while (addrs && dma_len > 0) {
+			if (WARN_ON(dma_index >= max_entries))
+				return -1;
+			addrs[dma_index] = addr;
 			addr += PAGE_SIZE;
-			len -= PAGE_SIZE;
-			index++;
+			dma_len -= PAGE_SIZE;
+			dma_index++;
 		}
 	}
 	return 0;
-- 
2.17.1

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
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Re: [PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Shane Francis]

On Fri, Mar 27, 2020 at 8:24 AM Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
>
> Scatterlist elements contains both pages and DMA addresses, but in general,
> one cannot assume 1:1 relation between them. The sg->length is the size of
> the physical memory chunk described by sg->page, while sg_dma_length(sg) is
> the size of the DMA (IO virtual) chunk described by sg_dma_address(sg).
>
> The proper way of extracting both: pages and DMA addresses of the whole
> buffer described by a scatterlist it to iterate independently over the
> sg->pages/sg->length and sg_dma_address(sg)/sg_dma_len(sg) entries.
>
> Fixes: 42e67b479eab ("drm/prime: use dma length macro when mapping sg")
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
> This fixes the following kernel panic observed on ARM 32bit Samsung
> Exynos5250-based Snow Chromebook since linux-next 20200326, which
> introduced the commit 42e67b479eab ("drm/prime: use dma length macro when
> mapping sg"):
>
>  [drm] Initialized panfrost 1.1.0 20180908 for 11800000.gpu on minor 0
>  [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
>  exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
>  exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
>  exynos-drm exynos-drm: bound 145b0000.dp-controller (ops exynos_dp_ops)
>  exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops)
>  [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
>  ------------[ cut here ]------------
>  WARNING: CPU: 0 PID: 12 at mm/vmalloc.c:163 vmap_page_range_noflush+0x18c/0x1b0
>  Modules linked in:
>  CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>  Hardware name: Samsung Exynos (Flattened Device Tree)
>  Workqueue: events deferred_probe_work_func
>  [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>  [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>  [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
>  [<c01271a0>] (__warn) from [<c0127268>] (warn_slowpath_fmt+0xb0/0xb8)
>  [<c0127268>] (warn_slowpath_fmt) from [<c0294fdc>] (vmap_page_range_noflush+0x18c/0x1b0)
>  [<c0294fdc>] (vmap_page_range_noflush) from [<c02952fc>] (map_vm_area+0x30/0x6c)
>  [<c02952fc>] (map_vm_area) from [<c0298df8>] (vmap+0x64/0x80)
>  [<c0298df8>] (vmap) from [<c05f71f4>] (exynos_drm_fbdev_create+0x148/0x270)
>  [<c05f71f4>] (exynos_drm_fbdev_create) from [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock+0x388/0x5dc)
>  [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock) from [<c05f743c>] (exynos_drm_fbdev_init+0x78/0xe0)
>  [<c05f743c>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
>  [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
>  [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
>  [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
>  [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
>  [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
>  [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
>  [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
>  [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
>  [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
>  [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
>  [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>  [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>  [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>  [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>  Exception stack(0xee8fdfb0 to 0xee8fdff8)
>  dfa0:                                     00000000 00000000 00000000 00000000
>  dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>  dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>  irq event stamp: 54037
>  hardirqs last  enabled at (54055): [<c019ed50>] console_unlock+0x58c/0x6a8
>  hardirqs last disabled at (54062): [<c019e890>] console_unlock+0xcc/0x6a8
>  softirqs last  enabled at (54078): [<c0101724>] __do_softirq+0x4fc/0x5f4
>  softirqs last disabled at (54089): [<c0130248>] irq_exit+0x16c/0x170
>  ---[ end trace 74519922e0e4625d ]---
>  exynos4-fb 14400000.fimd: [drm:exynos_drm_fbdev_create] *ERROR* failed to map pages to kernel space.
>  exynos-drm exynos-drm: [drm:exynos_drm_fbdev_init] *ERROR* failed to set up hw configuration.
>  ------------[ cut here ]------------
>  WARNING: CPU: 0 PID: 12 at kernel/locking/mutex-debug.c:103 mutex_destroy+0x84/0x88
>  DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock))
>  Modules linked in:
>  CPU: 0 PID: 12 Comm: kworker/0:1 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>  Hardware name: Samsung Exynos (Flattened Device Tree)
>  Workqueue: events deferred_probe_work_func
>  [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>  [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>  [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
>  [<c01271a0>] (__warn) from [<c012722c>] (warn_slowpath_fmt+0x74/0xb8)
>  [<c012722c>] (warn_slowpath_fmt) from [<c01892a4>] (mutex_destroy+0x84/0x88)
>  [<c01892a4>] (mutex_destroy) from [<c05be1a4>] (drm_fb_helper_fini.part.1+0x9c/0xd4)
>  [<c05be1a4>] (drm_fb_helper_fini.part.1) from [<c05f7464>] (exynos_drm_fbdev_init+0xa0/0xe0)
>  [<c05f7464>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
>  [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
>  [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
>  [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
>  [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
>  [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
>  [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
>  [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
>  [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
>  [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
>  [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
>  [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>  [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>  [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>  [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>  Exception stack(0xee8fdfb0 to 0xee8fdff8)
>  dfa0:                                     00000000 00000000 00000000 00000000
>  dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>  dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>  irq event stamp: 56283
>  hardirqs last  enabled at (56283): [<c02b189c>] kfree+0x198/0x3e4
>  hardirqs last disabled at (56282): [<c02b17d0>] kfree+0xcc/0x3e4
>  softirqs last  enabled at (56262): [<c0101724>] __do_softirq+0x4fc/0x5f4
>  softirqs last disabled at (56255): [<c0130248>] irq_exit+0x16c/0x170
>  ---[ end trace 74519922e0e4625e ]---
>  exynos-sysmmu 14640000.sysmmu: 14400000.fimd: PAGE FAULT occurred at 0x20000000
>  ------------[ cut here ]------------
>  kernel BUG at drivers/iommu/exynos-iommu.c:447!
>  Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>  Modules linked in:
>  CPU: 0 PID: 52 Comm: kworker/0:2 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>  Hardware name: Samsung Exynos (Flattened Device Tree)
>  Workqueue: events output_poll_execute
>  PC is at exynos_sysmmu_irq+0x210/0x258
>  LR is at report_iommu_fault+0x144/0x1cc
>  pc : [<c05a6e34>]    lr : [<c05a13ec>]    psr: a0000193
>  sp : cfafdbe8  ip : 2d495ebb  fp : 00000200
>  r10: eeb187e0  r9 : 20000000  r8 : cf300000
>  r7 : c11d4fb0  r6 : eeb187c0  r5 : 00000000  r4 : c0b59f74
>  r3 : cfafc000  r2 : 00010001  r1 : 00000000  r0 : ffffffda
>  Flags: NzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
>  Control: 10c5387d  Table: 4000406a  DAC: 00000051
>  Process kworker/0:2 (pid: 52, stack limit = 0x(ptrval))
>  Stack: (0xcfafdbe8 to 0xcfafe000)
>  ...
>  [<c05a6e34>] (exynos_sysmmu_irq) from [<c01a24f4>] (__handle_irq_event_percpu+0x68/0x42c)
>  [<c01a24f4>] (__handle_irq_event_percpu) from [<c01a28e4>] (handle_irq_event_percpu+0x2c/0x7c)
>  [<c01a28e4>] (handle_irq_event_percpu) from [<c01a296c>] (handle_irq_event+0x38/0x5c)
>  [<c01a296c>] (handle_irq_event) from [<c01a7160>] (handle_level_irq+0xcc/0x150)
>  [<c01a7160>] (handle_level_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
>  [<c01a1574>] (generic_handle_irq) from [<c0509a5c>] (combiner_handle_cascade_irq+0x8c/0xdc)
>  [<c0509a5c>] (combiner_handle_cascade_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
>  [<c01a1574>] (generic_handle_irq) from [<c01a1bbc>] (__handle_domain_irq+0x7c/0xec)
>  [<c01a1bbc>] (__handle_domain_irq) from [<c050a024>] (gic_handle_irq+0x58/0x9c)
>  [<c050a024>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
>  Exception stack(0xcfafdd00 to 0xcfafdd48)
>  dd00: c02b189c 00000000 2df3c000 00000000 cf2ed3c0 ee801cc0 60000113 ef1ddda0
>  dd20: c05d5500 00000000 cf2c9800 cf2ea8b8 00003220 cfafdd50 c02b189c c02b18a0
>  dd40: 60000113 ffffffff
>  [<c0100af0>] (__irq_svc) from [<c02b18a0>] (kfree+0x19c/0x3e4)
>  [<c02b18a0>] (kfree) from [<c05d5500>] (drm_atomic_state_default_clear+0x1b8/0x2dc)
>  [<c05d5500>] (drm_atomic_state_default_clear) from [<c05d5650>] (__drm_atomic_state_free+0x10/0x50)
>  [<c05d5650>] (__drm_atomic_state_free) from [<c05e9d88>] (drm_client_modeset_commit_atomic+0x240/0x26c)
>  [<c05e9d88>] (drm_client_modeset_commit_atomic) from [<c05e9df8>] (drm_client_modeset_commit_locked+0x44/0x1d0)
>  [<c05e9df8>] (drm_client_modeset_commit_locked) from [<c05e9fa8>] (drm_client_modeset_commit+0x24/0x40)
>  [<c05e9fa8>] (drm_client_modeset_commit) from [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked+0x58/0xa4)
>  [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked) from [<c05be468>] (drm_fb_helper_set_par+0x30/0x5c)
>  [<c05be468>] (drm_fb_helper_set_par) from [<c05be538>] (drm_fb_helper_hotplug_event.part.5+0xa4/0xbc)
>  [<c05be538>] (drm_fb_helper_hotplug_event.part.5) from [<c05ac148>] (drm_kms_helper_hotplug_event+0x24/0x30)
>  [<c05ac148>] (drm_kms_helper_hotplug_event) from [<c05ac238>] (output_poll_execute+0xb8/0x1b4)
>  [<c05ac238>] (output_poll_execute) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>  [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>  [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>  [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>  Exception stack(0xcfafdfb0 to 0xcfafdff8)
>  dfa0:                                     00000000 00000000 00000000 00000000
>  dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>  dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>  Code: e34c00de e300119e ebee00e1 eaffff81 (e7f001f2)
>  ---[ end trace 74519922e0e4625f ]---
>  Kernel panic - not syncing: Fatal exception in interrupt
>  CPU1: stopping
>  CPU: 1 PID: 0 Comm: swapper/1 Tainted: G      D W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>  Hardware name: Samsung Exynos (Flattened Device Tree)
>  [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>  [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>  [<c0a78178>] (dump_stack) from [<c0110ad4>] (handle_IPI+0x3b4/0x440)
>  [<c0110ad4>] (handle_IPI) from [<c050a064>] (gic_handle_irq+0x98/0x9c)
>  [<c050a064>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
>  Exception stack(0xee8fff58 to 0xee8fffa0)
>  ff40:                                                       c0109534 00000000
>  ff60: 2df50000 00000000 ee8fe000 c1108ee8 c1108f2c 00000002 00000000 c0de63c0
>  ff80: 00000000 c1075fe8 2d495ebb ee8fffa8 c0109534 c0109538 60000013 ffffffff
>  [<c0100af0>] (__irq_svc) from [<c0109538>] (arch_cpu_idle+0x24/0x44)
>  [<c0109538>] (arch_cpu_idle) from [<c0163a74>] (do_idle+0x1d8/0x2d4)
>  [<c0163a74>] (do_idle) from [<c0163f24>] (cpu_startup_entry+0x18/0x1c)
>  [<c0163f24>] (cpu_startup_entry) from [<401018ac>] (0x401018ac)
>  ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
> ---
>  drivers/gpu/drm/drm_prime.c | 30 ++++++++++++++++++------------
>  1 file changed, 18 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 1de2cde2277c..424db18987f6 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -962,27 +962,33 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
>         unsigned count;
>         struct scatterlist *sg;
>         struct page *page;
> -       u32 len, index;
> +       u32 page_len, page_index;
>         dma_addr_t addr;
> +       u32 dma_len, dma_index;
>
> -       index = 0;
> +       page_index = 0;
> +       dma_index = 0;
>         for_each_sg(sgt->sgl, sg, sgt->nents, count) {
> -               len = sg_dma_len(sg);
> +               page_len = sg->length;
>                 page = sg_page(sg);
> +               dma_len = sg_dma_len(sg);
>                 addr = sg_dma_address(sg);
>
> -               while (len > 0) {
> -                       if (WARN_ON(index >= max_entries))
> +               while (pages && page_len > 0) {
> +                       if (WARN_ON(page_index >= max_entries))
>                                 return -1;
> -                       if (pages)
> -                               pages[index] = page;
> -                       if (addrs)
> -                               addrs[index] = addr;
> -
> +                       pages[page_index] = page;
>                         page++;
> +                       page_len -= PAGE_SIZE;
> +                       page_index++;
> +               }
> +               while (addrs && dma_len > 0) {
> +                       if (WARN_ON(dma_index >= max_entries))
> +                               return -1;
> +                       addrs[dma_index] = addr;
>                         addr += PAGE_SIZE;
> -                       len -= PAGE_SIZE;
> -                       index++;
> +                       dma_len -= PAGE_SIZE;
> +                       dma_index++;
>                 }
>         }
>         return 0;
> --
> 2.17.1
>

I have tested the above patch against my original issues with amdgpu
and radeon drivers and everything is still working as expected.

Sorry I missed this in my original patches.

Re: [PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Shane Francis]

On Fri, Mar 27, 2020 at 8:24 AM Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
>
> Scatterlist elements contains both pages and DMA addresses, but in general,
> one cannot assume 1:1 relation between them. The sg->length is the size of
> the physical memory chunk described by sg->page, while sg_dma_length(sg) is
> the size of the DMA (IO virtual) chunk described by sg_dma_address(sg).
>
> The proper way of extracting both: pages and DMA addresses of the whole
> buffer described by a scatterlist it to iterate independently over the
> sg->pages/sg->length and sg_dma_address(sg)/sg_dma_len(sg) entries.
>
> Fixes: 42e67b479eab ("drm/prime: use dma length macro when mapping sg")
> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
> ---
> This fixes the following kernel panic observed on ARM 32bit Samsung
> Exynos5250-based Snow Chromebook since linux-next 20200326, which
> introduced the commit 42e67b479eab ("drm/prime: use dma length macro when
> mapping sg"):
>
>  [drm] Initialized panfrost 1.1.0 20180908 for 11800000.gpu on minor 0
>  [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
>  exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
>  exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
>  exynos-drm exynos-drm: bound 145b0000.dp-controller (ops exynos_dp_ops)
>  exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops)
>  [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
>  ------------[ cut here ]------------
>  WARNING: CPU: 0 PID: 12 at mm/vmalloc.c:163 vmap_page_range_noflush+0x18c/0x1b0
>  Modules linked in:
>  CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>  Hardware name: Samsung Exynos (Flattened Device Tree)
>  Workqueue: events deferred_probe_work_func
>  [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>  [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>  [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
>  [<c01271a0>] (__warn) from [<c0127268>] (warn_slowpath_fmt+0xb0/0xb8)
>  [<c0127268>] (warn_slowpath_fmt) from [<c0294fdc>] (vmap_page_range_noflush+0x18c/0x1b0)
>  [<c0294fdc>] (vmap_page_range_noflush) from [<c02952fc>] (map_vm_area+0x30/0x6c)
>  [<c02952fc>] (map_vm_area) from [<c0298df8>] (vmap+0x64/0x80)
>  [<c0298df8>] (vmap) from [<c05f71f4>] (exynos_drm_fbdev_create+0x148/0x270)
>  [<c05f71f4>] (exynos_drm_fbdev_create) from [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock+0x388/0x5dc)
>  [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock) from [<c05f743c>] (exynos_drm_fbdev_init+0x78/0xe0)
>  [<c05f743c>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
>  [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
>  [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
>  [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
>  [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
>  [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
>  [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
>  [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
>  [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
>  [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
>  [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
>  [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>  [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>  [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>  [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>  Exception stack(0xee8fdfb0 to 0xee8fdff8)
>  dfa0:                                     00000000 00000000 00000000 00000000
>  dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>  dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>  irq event stamp: 54037
>  hardirqs last  enabled at (54055): [<c019ed50>] console_unlock+0x58c/0x6a8
>  hardirqs last disabled at (54062): [<c019e890>] console_unlock+0xcc/0x6a8
>  softirqs last  enabled at (54078): [<c0101724>] __do_softirq+0x4fc/0x5f4
>  softirqs last disabled at (54089): [<c0130248>] irq_exit+0x16c/0x170
>  ---[ end trace 74519922e0e4625d ]---
>  exynos4-fb 14400000.fimd: [drm:exynos_drm_fbdev_create] *ERROR* failed to map pages to kernel space.
>  exynos-drm exynos-drm: [drm:exynos_drm_fbdev_init] *ERROR* failed to set up hw configuration.
>  ------------[ cut here ]------------
>  WARNING: CPU: 0 PID: 12 at kernel/locking/mutex-debug.c:103 mutex_destroy+0x84/0x88
>  DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock))
>  Modules linked in:
>  CPU: 0 PID: 12 Comm: kworker/0:1 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>  Hardware name: Samsung Exynos (Flattened Device Tree)
>  Workqueue: events deferred_probe_work_func
>  [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>  [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>  [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
>  [<c01271a0>] (__warn) from [<c012722c>] (warn_slowpath_fmt+0x74/0xb8)
>  [<c012722c>] (warn_slowpath_fmt) from [<c01892a4>] (mutex_destroy+0x84/0x88)
>  [<c01892a4>] (mutex_destroy) from [<c05be1a4>] (drm_fb_helper_fini.part.1+0x9c/0xd4)
>  [<c05be1a4>] (drm_fb_helper_fini.part.1) from [<c05f7464>] (exynos_drm_fbdev_init+0xa0/0xe0)
>  [<c05f7464>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
>  [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
>  [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
>  [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
>  [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
>  [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
>  [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
>  [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
>  [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
>  [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
>  [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
>  [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>  [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>  [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>  [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>  Exception stack(0xee8fdfb0 to 0xee8fdff8)
>  dfa0:                                     00000000 00000000 00000000 00000000
>  dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>  dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>  irq event stamp: 56283
>  hardirqs last  enabled at (56283): [<c02b189c>] kfree+0x198/0x3e4
>  hardirqs last disabled at (56282): [<c02b17d0>] kfree+0xcc/0x3e4
>  softirqs last  enabled at (56262): [<c0101724>] __do_softirq+0x4fc/0x5f4
>  softirqs last disabled at (56255): [<c0130248>] irq_exit+0x16c/0x170
>  ---[ end trace 74519922e0e4625e ]---
>  exynos-sysmmu 14640000.sysmmu: 14400000.fimd: PAGE FAULT occurred at 0x20000000
>  ------------[ cut here ]------------
>  kernel BUG at drivers/iommu/exynos-iommu.c:447!
>  Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>  Modules linked in:
>  CPU: 0 PID: 52 Comm: kworker/0:2 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>  Hardware name: Samsung Exynos (Flattened Device Tree)
>  Workqueue: events output_poll_execute
>  PC is at exynos_sysmmu_irq+0x210/0x258
>  LR is at report_iommu_fault+0x144/0x1cc
>  pc : [<c05a6e34>]    lr : [<c05a13ec>]    psr: a0000193
>  sp : cfafdbe8  ip : 2d495ebb  fp : 00000200
>  r10: eeb187e0  r9 : 20000000  r8 : cf300000
>  r7 : c11d4fb0  r6 : eeb187c0  r5 : 00000000  r4 : c0b59f74
>  r3 : cfafc000  r2 : 00010001  r1 : 00000000  r0 : ffffffda
>  Flags: NzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
>  Control: 10c5387d  Table: 4000406a  DAC: 00000051
>  Process kworker/0:2 (pid: 52, stack limit = 0x(ptrval))
>  Stack: (0xcfafdbe8 to 0xcfafe000)
>  ...
>  [<c05a6e34>] (exynos_sysmmu_irq) from [<c01a24f4>] (__handle_irq_event_percpu+0x68/0x42c)
>  [<c01a24f4>] (__handle_irq_event_percpu) from [<c01a28e4>] (handle_irq_event_percpu+0x2c/0x7c)
>  [<c01a28e4>] (handle_irq_event_percpu) from [<c01a296c>] (handle_irq_event+0x38/0x5c)
>  [<c01a296c>] (handle_irq_event) from [<c01a7160>] (handle_level_irq+0xcc/0x150)
>  [<c01a7160>] (handle_level_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
>  [<c01a1574>] (generic_handle_irq) from [<c0509a5c>] (combiner_handle_cascade_irq+0x8c/0xdc)
>  [<c0509a5c>] (combiner_handle_cascade_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
>  [<c01a1574>] (generic_handle_irq) from [<c01a1bbc>] (__handle_domain_irq+0x7c/0xec)
>  [<c01a1bbc>] (__handle_domain_irq) from [<c050a024>] (gic_handle_irq+0x58/0x9c)
>  [<c050a024>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
>  Exception stack(0xcfafdd00 to 0xcfafdd48)
>  dd00: c02b189c 00000000 2df3c000 00000000 cf2ed3c0 ee801cc0 60000113 ef1ddda0
>  dd20: c05d5500 00000000 cf2c9800 cf2ea8b8 00003220 cfafdd50 c02b189c c02b18a0
>  dd40: 60000113 ffffffff
>  [<c0100af0>] (__irq_svc) from [<c02b18a0>] (kfree+0x19c/0x3e4)
>  [<c02b18a0>] (kfree) from [<c05d5500>] (drm_atomic_state_default_clear+0x1b8/0x2dc)
>  [<c05d5500>] (drm_atomic_state_default_clear) from [<c05d5650>] (__drm_atomic_state_free+0x10/0x50)
>  [<c05d5650>] (__drm_atomic_state_free) from [<c05e9d88>] (drm_client_modeset_commit_atomic+0x240/0x26c)
>  [<c05e9d88>] (drm_client_modeset_commit_atomic) from [<c05e9df8>] (drm_client_modeset_commit_locked+0x44/0x1d0)
>  [<c05e9df8>] (drm_client_modeset_commit_locked) from [<c05e9fa8>] (drm_client_modeset_commit+0x24/0x40)
>  [<c05e9fa8>] (drm_client_modeset_commit) from [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked+0x58/0xa4)
>  [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked) from [<c05be468>] (drm_fb_helper_set_par+0x30/0x5c)
>  [<c05be468>] (drm_fb_helper_set_par) from [<c05be538>] (drm_fb_helper_hotplug_event.part.5+0xa4/0xbc)
>  [<c05be538>] (drm_fb_helper_hotplug_event.part.5) from [<c05ac148>] (drm_kms_helper_hotplug_event+0x24/0x30)
>  [<c05ac148>] (drm_kms_helper_hotplug_event) from [<c05ac238>] (output_poll_execute+0xb8/0x1b4)
>  [<c05ac238>] (output_poll_execute) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>  [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>  [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>  [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>  Exception stack(0xcfafdfb0 to 0xcfafdff8)
>  dfa0:                                     00000000 00000000 00000000 00000000
>  dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>  dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>  Code: e34c00de e300119e ebee00e1 eaffff81 (e7f001f2)
>  ---[ end trace 74519922e0e4625f ]---
>  Kernel panic - not syncing: Fatal exception in interrupt
>  CPU1: stopping
>  CPU: 1 PID: 0 Comm: swapper/1 Tainted: G      D W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>  Hardware name: Samsung Exynos (Flattened Device Tree)
>  [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>  [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>  [<c0a78178>] (dump_stack) from [<c0110ad4>] (handle_IPI+0x3b4/0x440)
>  [<c0110ad4>] (handle_IPI) from [<c050a064>] (gic_handle_irq+0x98/0x9c)
>  [<c050a064>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
>  Exception stack(0xee8fff58 to 0xee8fffa0)
>  ff40:                                                       c0109534 00000000
>  ff60: 2df50000 00000000 ee8fe000 c1108ee8 c1108f2c 00000002 00000000 c0de63c0
>  ff80: 00000000 c1075fe8 2d495ebb ee8fffa8 c0109534 c0109538 60000013 ffffffff
>  [<c0100af0>] (__irq_svc) from [<c0109538>] (arch_cpu_idle+0x24/0x44)
>  [<c0109538>] (arch_cpu_idle) from [<c0163a74>] (do_idle+0x1d8/0x2d4)
>  [<c0163a74>] (do_idle) from [<c0163f24>] (cpu_startup_entry+0x18/0x1c)
>  [<c0163f24>] (cpu_startup_entry) from [<401018ac>] (0x401018ac)
>  ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
> ---
>  drivers/gpu/drm/drm_prime.c | 30 ++++++++++++++++++------------
>  1 file changed, 18 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 1de2cde2277c..424db18987f6 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -962,27 +962,33 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
>         unsigned count;
>         struct scatterlist *sg;
>         struct page *page;
> -       u32 len, index;
> +       u32 page_len, page_index;
>         dma_addr_t addr;
> +       u32 dma_len, dma_index;
>
> -       index = 0;
> +       page_index = 0;
> +       dma_index = 0;
>         for_each_sg(sgt->sgl, sg, sgt->nents, count) {
> -               len = sg_dma_len(sg);
> +               page_len = sg->length;
>                 page = sg_page(sg);
> +               dma_len = sg_dma_len(sg);
>                 addr = sg_dma_address(sg);
>
> -               while (len > 0) {
> -                       if (WARN_ON(index >= max_entries))
> +               while (pages && page_len > 0) {
> +                       if (WARN_ON(page_index >= max_entries))
>                                 return -1;
> -                       if (pages)
> -                               pages[index] = page;
> -                       if (addrs)
> -                               addrs[index] = addr;
> -
> +                       pages[page_index] = page;
>                         page++;
> +                       page_len -= PAGE_SIZE;
> +                       page_index++;
> +               }
> +               while (addrs && dma_len > 0) {
> +                       if (WARN_ON(dma_index >= max_entries))
> +                               return -1;
> +                       addrs[dma_index] = addr;
>                         addr += PAGE_SIZE;
> -                       len -= PAGE_SIZE;
> -                       index++;
> +                       dma_len -= PAGE_SIZE;
> +                       dma_index++;
>                 }
>         }
>         return 0;
> --
> 2.17.1
>

I have tested the above patch against my original issues with amdgpu
and radeon drivers and everything is still working as expected.

Sorry I missed this in my original patches.
_______________________________________________
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Re: [PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Marek Szyprowski]

Hi Shane

On 2020-03-27 09:55, Shane Francis wrote:
> On Fri, Mar 27, 2020 at 8:24 AM Marek Szyprowski
> <m.szyprowski@samsung.com> wrote:
>> Scatterlist elements contains both pages and DMA addresses, but in general,
>> one cannot assume 1:1 relation between them. The sg->length is the size of
>> the physical memory chunk described by sg->page, while sg_dma_length(sg) is
>> the size of the DMA (IO virtual) chunk described by sg_dma_address(sg).
>>
>> The proper way of extracting both: pages and DMA addresses of the whole
>> buffer described by a scatterlist it to iterate independently over the
>> sg->pages/sg->length and sg_dma_address(sg)/sg_dma_len(sg) entries.
>>
>> Fixes: 42e67b479eab ("drm/prime: use dma length macro when mapping sg")
>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> ---
>> This fixes the following kernel panic observed on ARM 32bit Samsung
>> Exynos5250-based Snow Chromebook since linux-next 20200326, which
>> introduced the commit 42e67b479eab ("drm/prime: use dma length macro when
>> mapping sg"):
>>
>>   [drm] Initialized panfrost 1.1.0 20180908 for 11800000.gpu on minor 0
>>   [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
>>   exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
>>   exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
>>   exynos-drm exynos-drm: bound 145b0000.dp-controller (ops exynos_dp_ops)
>>   exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops)
>>   [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
>>   ------------[ cut here ]------------
>>   WARNING: CPU: 0 PID: 12 at mm/vmalloc.c:163 vmap_page_range_noflush+0x18c/0x1b0
>>   Modules linked in:
>>   CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>>   Hardware name: Samsung Exynos (Flattened Device Tree)
>>   Workqueue: events deferred_probe_work_func
>>   [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>>   [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>>   [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
>>   [<c01271a0>] (__warn) from [<c0127268>] (warn_slowpath_fmt+0xb0/0xb8)
>>   [<c0127268>] (warn_slowpath_fmt) from [<c0294fdc>] (vmap_page_range_noflush+0x18c/0x1b0)
>>   [<c0294fdc>] (vmap_page_range_noflush) from [<c02952fc>] (map_vm_area+0x30/0x6c)
>>   [<c02952fc>] (map_vm_area) from [<c0298df8>] (vmap+0x64/0x80)
>>   [<c0298df8>] (vmap) from [<c05f71f4>] (exynos_drm_fbdev_create+0x148/0x270)
>>   [<c05f71f4>] (exynos_drm_fbdev_create) from [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock+0x388/0x5dc)
>>   [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock) from [<c05f743c>] (exynos_drm_fbdev_init+0x78/0xe0)
>>   [<c05f743c>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
>>   [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
>>   [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
>>   [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
>>   [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
>>   [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
>>   [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
>>   [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
>>   [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
>>   [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
>>   [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
>>   [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>>   [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>>   [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>>   [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>>   Exception stack(0xee8fdfb0 to 0xee8fdff8)
>>   dfa0:                                     00000000 00000000 00000000 00000000
>>   dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>>   dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>>   irq event stamp: 54037
>>   hardirqs last  enabled at (54055): [<c019ed50>] console_unlock+0x58c/0x6a8
>>   hardirqs last disabled at (54062): [<c019e890>] console_unlock+0xcc/0x6a8
>>   softirqs last  enabled at (54078): [<c0101724>] __do_softirq+0x4fc/0x5f4
>>   softirqs last disabled at (54089): [<c0130248>] irq_exit+0x16c/0x170
>>   ---[ end trace 74519922e0e4625d ]---
>>   exynos4-fb 14400000.fimd: [drm:exynos_drm_fbdev_create] *ERROR* failed to map pages to kernel space.
>>   exynos-drm exynos-drm: [drm:exynos_drm_fbdev_init] *ERROR* failed to set up hw configuration.
>>   ------------[ cut here ]------------
>>   WARNING: CPU: 0 PID: 12 at kernel/locking/mutex-debug.c:103 mutex_destroy+0x84/0x88
>>   DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock))
>>   Modules linked in:
>>   CPU: 0 PID: 12 Comm: kworker/0:1 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>>   Hardware name: Samsung Exynos (Flattened Device Tree)
>>   Workqueue: events deferred_probe_work_func
>>   [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>>   [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>>   [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
>>   [<c01271a0>] (__warn) from [<c012722c>] (warn_slowpath_fmt+0x74/0xb8)
>>   [<c012722c>] (warn_slowpath_fmt) from [<c01892a4>] (mutex_destroy+0x84/0x88)
>>   [<c01892a4>] (mutex_destroy) from [<c05be1a4>] (drm_fb_helper_fini.part.1+0x9c/0xd4)
>>   [<c05be1a4>] (drm_fb_helper_fini.part.1) from [<c05f7464>] (exynos_drm_fbdev_init+0xa0/0xe0)
>>   [<c05f7464>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
>>   [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
>>   [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
>>   [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
>>   [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
>>   [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
>>   [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
>>   [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
>>   [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
>>   [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
>>   [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
>>   [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>>   [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>>   [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>>   [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>>   Exception stack(0xee8fdfb0 to 0xee8fdff8)
>>   dfa0:                                     00000000 00000000 00000000 00000000
>>   dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>>   dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>>   irq event stamp: 56283
>>   hardirqs last  enabled at (56283): [<c02b189c>] kfree+0x198/0x3e4
>>   hardirqs last disabled at (56282): [<c02b17d0>] kfree+0xcc/0x3e4
>>   softirqs last  enabled at (56262): [<c0101724>] __do_softirq+0x4fc/0x5f4
>>   softirqs last disabled at (56255): [<c0130248>] irq_exit+0x16c/0x170
>>   ---[ end trace 74519922e0e4625e ]---
>>   exynos-sysmmu 14640000.sysmmu: 14400000.fimd: PAGE FAULT occurred at 0x20000000
>>   ------------[ cut here ]------------
>>   kernel BUG at drivers/iommu/exynos-iommu.c:447!
>>   Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>>   Modules linked in:
>>   CPU: 0 PID: 52 Comm: kworker/0:2 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>>   Hardware name: Samsung Exynos (Flattened Device Tree)
>>   Workqueue: events output_poll_execute
>>   PC is at exynos_sysmmu_irq+0x210/0x258
>>   LR is at report_iommu_fault+0x144/0x1cc
>>   pc : [<c05a6e34>]    lr : [<c05a13ec>]    psr: a0000193
>>   sp : cfafdbe8  ip : 2d495ebb  fp : 00000200
>>   r10: eeb187e0  r9 : 20000000  r8 : cf300000
>>   r7 : c11d4fb0  r6 : eeb187c0  r5 : 00000000  r4 : c0b59f74
>>   r3 : cfafc000  r2 : 00010001  r1 : 00000000  r0 : ffffffda
>>   Flags: NzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
>>   Control: 10c5387d  Table: 4000406a  DAC: 00000051
>>   Process kworker/0:2 (pid: 52, stack limit = 0x(ptrval))
>>   Stack: (0xcfafdbe8 to 0xcfafe000)
>>   ...
>>   [<c05a6e34>] (exynos_sysmmu_irq) from [<c01a24f4>] (__handle_irq_event_percpu+0x68/0x42c)
>>   [<c01a24f4>] (__handle_irq_event_percpu) from [<c01a28e4>] (handle_irq_event_percpu+0x2c/0x7c)
>>   [<c01a28e4>] (handle_irq_event_percpu) from [<c01a296c>] (handle_irq_event+0x38/0x5c)
>>   [<c01a296c>] (handle_irq_event) from [<c01a7160>] (handle_level_irq+0xcc/0x150)
>>   [<c01a7160>] (handle_level_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
>>   [<c01a1574>] (generic_handle_irq) from [<c0509a5c>] (combiner_handle_cascade_irq+0x8c/0xdc)
>>   [<c0509a5c>] (combiner_handle_cascade_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
>>   [<c01a1574>] (generic_handle_irq) from [<c01a1bbc>] (__handle_domain_irq+0x7c/0xec)
>>   [<c01a1bbc>] (__handle_domain_irq) from [<c050a024>] (gic_handle_irq+0x58/0x9c)
>>   [<c050a024>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
>>   Exception stack(0xcfafdd00 to 0xcfafdd48)
>>   dd00: c02b189c 00000000 2df3c000 00000000 cf2ed3c0 ee801cc0 60000113 ef1ddda0
>>   dd20: c05d5500 00000000 cf2c9800 cf2ea8b8 00003220 cfafdd50 c02b189c c02b18a0
>>   dd40: 60000113 ffffffff
>>   [<c0100af0>] (__irq_svc) from [<c02b18a0>] (kfree+0x19c/0x3e4)
>>   [<c02b18a0>] (kfree) from [<c05d5500>] (drm_atomic_state_default_clear+0x1b8/0x2dc)
>>   [<c05d5500>] (drm_atomic_state_default_clear) from [<c05d5650>] (__drm_atomic_state_free+0x10/0x50)
>>   [<c05d5650>] (__drm_atomic_state_free) from [<c05e9d88>] (drm_client_modeset_commit_atomic+0x240/0x26c)
>>   [<c05e9d88>] (drm_client_modeset_commit_atomic) from [<c05e9df8>] (drm_client_modeset_commit_locked+0x44/0x1d0)
>>   [<c05e9df8>] (drm_client_modeset_commit_locked) from [<c05e9fa8>] (drm_client_modeset_commit+0x24/0x40)
>>   [<c05e9fa8>] (drm_client_modeset_commit) from [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked+0x58/0xa4)
>>   [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked) from [<c05be468>] (drm_fb_helper_set_par+0x30/0x5c)
>>   [<c05be468>] (drm_fb_helper_set_par) from [<c05be538>] (drm_fb_helper_hotplug_event.part.5+0xa4/0xbc)
>>   [<c05be538>] (drm_fb_helper_hotplug_event.part.5) from [<c05ac148>] (drm_kms_helper_hotplug_event+0x24/0x30)
>>   [<c05ac148>] (drm_kms_helper_hotplug_event) from [<c05ac238>] (output_poll_execute+0xb8/0x1b4)
>>   [<c05ac238>] (output_poll_execute) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>>   [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>>   [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>>   [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>>   Exception stack(0xcfafdfb0 to 0xcfafdff8)
>>   dfa0:                                     00000000 00000000 00000000 00000000
>>   dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>>   dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>>   Code: e34c00de e300119e ebee00e1 eaffff81 (e7f001f2)
>>   ---[ end trace 74519922e0e4625f ]---
>>   Kernel panic - not syncing: Fatal exception in interrupt
>>   CPU1: stopping
>>   CPU: 1 PID: 0 Comm: swapper/1 Tainted: G      D W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>>   Hardware name: Samsung Exynos (Flattened Device Tree)
>>   [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>>   [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>>   [<c0a78178>] (dump_stack) from [<c0110ad4>] (handle_IPI+0x3b4/0x440)
>>   [<c0110ad4>] (handle_IPI) from [<c050a064>] (gic_handle_irq+0x98/0x9c)
>>   [<c050a064>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
>>   Exception stack(0xee8fff58 to 0xee8fffa0)
>>   ff40:                                                       c0109534 00000000
>>   ff60: 2df50000 00000000 ee8fe000 c1108ee8 c1108f2c 00000002 00000000 c0de63c0
>>   ff80: 00000000 c1075fe8 2d495ebb ee8fffa8 c0109534 c0109538 60000013 ffffffff
>>   [<c0100af0>] (__irq_svc) from [<c0109538>] (arch_cpu_idle+0x24/0x44)
>>   [<c0109538>] (arch_cpu_idle) from [<c0163a74>] (do_idle+0x1d8/0x2d4)
>>   [<c0163a74>] (do_idle) from [<c0163f24>] (cpu_startup_entry+0x18/0x1c)
>>   [<c0163f24>] (cpu_startup_entry) from [<401018ac>] (0x401018ac)
>>   ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
>> ---
>>   drivers/gpu/drm/drm_prime.c | 30 ++++++++++++++++++------------
>>   1 file changed, 18 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
>> index 1de2cde2277c..424db18987f6 100644
>> --- a/drivers/gpu/drm/drm_prime.c
>> +++ b/drivers/gpu/drm/drm_prime.c
>> @@ -962,27 +962,33 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
>>          unsigned count;
>>          struct scatterlist *sg;
>>          struct page *page;
>> -       u32 len, index;
>> +       u32 page_len, page_index;
>>          dma_addr_t addr;
>> +       u32 dma_len, dma_index;
>>
>> -       index = 0;
>> +       page_index = 0;
>> +       dma_index = 0;
>>          for_each_sg(sgt->sgl, sg, sgt->nents, count) {
>> -               len = sg_dma_len(sg);
>> +               page_len = sg->length;
>>                  page = sg_page(sg);
>> +               dma_len = sg_dma_len(sg);
>>                  addr = sg_dma_address(sg);
>>
>> -               while (len > 0) {
>> -                       if (WARN_ON(index >= max_entries))
>> +               while (pages && page_len > 0) {
>> +                       if (WARN_ON(page_index >= max_entries))
>>                                  return -1;
>> -                       if (pages)
>> -                               pages[index] = page;
>> -                       if (addrs)
>> -                               addrs[index] = addr;
>> -
>> +                       pages[page_index] = page;
>>                          page++;
>> +                       page_len -= PAGE_SIZE;
>> +                       page_index++;
>> +               }
>> +               while (addrs && dma_len > 0) {
>> +                       if (WARN_ON(dma_index >= max_entries))
>> +                               return -1;
>> +                       addrs[dma_index] = addr;
>>                          addr += PAGE_SIZE;
>> -                       len -= PAGE_SIZE;
>> -                       index++;
>> +                       dma_len -= PAGE_SIZE;
>> +                       dma_index++;
>>                  }
>>          }
>>          return 0;
>> --
>> 2.17.1
>>
> I have tested the above patch against my original issues with amdgpu
> and radeon drivers and everything is still working as expected.
>
> Sorry I missed this in my original patches.

No problem. Thanks for testing!

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Marek Szyprowski]

Hi Shane

On 2020-03-27 09:55, Shane Francis wrote:
> On Fri, Mar 27, 2020 at 8:24 AM Marek Szyprowski
> <m.szyprowski@samsung.com> wrote:
>> Scatterlist elements contains both pages and DMA addresses, but in general,
>> one cannot assume 1:1 relation between them. The sg->length is the size of
>> the physical memory chunk described by sg->page, while sg_dma_length(sg) is
>> the size of the DMA (IO virtual) chunk described by sg_dma_address(sg).
>>
>> The proper way of extracting both: pages and DMA addresses of the whole
>> buffer described by a scatterlist it to iterate independently over the
>> sg->pages/sg->length and sg_dma_address(sg)/sg_dma_len(sg) entries.
>>
>> Fixes: 42e67b479eab ("drm/prime: use dma length macro when mapping sg")
>> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
>> ---
>> This fixes the following kernel panic observed on ARM 32bit Samsung
>> Exynos5250-based Snow Chromebook since linux-next 20200326, which
>> introduced the commit 42e67b479eab ("drm/prime: use dma length macro when
>> mapping sg"):
>>
>>   [drm] Initialized panfrost 1.1.0 20180908 for 11800000.gpu on minor 0
>>   [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
>>   exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
>>   exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
>>   exynos-drm exynos-drm: bound 145b0000.dp-controller (ops exynos_dp_ops)
>>   exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops)
>>   [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
>>   ------------[ cut here ]------------
>>   WARNING: CPU: 0 PID: 12 at mm/vmalloc.c:163 vmap_page_range_noflush+0x18c/0x1b0
>>   Modules linked in:
>>   CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>>   Hardware name: Samsung Exynos (Flattened Device Tree)
>>   Workqueue: events deferred_probe_work_func
>>   [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>>   [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>>   [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
>>   [<c01271a0>] (__warn) from [<c0127268>] (warn_slowpath_fmt+0xb0/0xb8)
>>   [<c0127268>] (warn_slowpath_fmt) from [<c0294fdc>] (vmap_page_range_noflush+0x18c/0x1b0)
>>   [<c0294fdc>] (vmap_page_range_noflush) from [<c02952fc>] (map_vm_area+0x30/0x6c)
>>   [<c02952fc>] (map_vm_area) from [<c0298df8>] (vmap+0x64/0x80)
>>   [<c0298df8>] (vmap) from [<c05f71f4>] (exynos_drm_fbdev_create+0x148/0x270)
>>   [<c05f71f4>] (exynos_drm_fbdev_create) from [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock+0x388/0x5dc)
>>   [<c05bde44>] (__drm_fb_helper_initial_config_and_unlock) from [<c05f743c>] (exynos_drm_fbdev_init+0x78/0xe0)
>>   [<c05f743c>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
>>   [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
>>   [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
>>   [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
>>   [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
>>   [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
>>   [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
>>   [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
>>   [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
>>   [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
>>   [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
>>   [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>>   [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>>   [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>>   [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>>   Exception stack(0xee8fdfb0 to 0xee8fdff8)
>>   dfa0:                                     00000000 00000000 00000000 00000000
>>   dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>>   dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>>   irq event stamp: 54037
>>   hardirqs last  enabled at (54055): [<c019ed50>] console_unlock+0x58c/0x6a8
>>   hardirqs last disabled at (54062): [<c019e890>] console_unlock+0xcc/0x6a8
>>   softirqs last  enabled at (54078): [<c0101724>] __do_softirq+0x4fc/0x5f4
>>   softirqs last disabled at (54089): [<c0130248>] irq_exit+0x16c/0x170
>>   ---[ end trace 74519922e0e4625d ]---
>>   exynos4-fb 14400000.fimd: [drm:exynos_drm_fbdev_create] *ERROR* failed to map pages to kernel space.
>>   exynos-drm exynos-drm: [drm:exynos_drm_fbdev_init] *ERROR* failed to set up hw configuration.
>>   ------------[ cut here ]------------
>>   WARNING: CPU: 0 PID: 12 at kernel/locking/mutex-debug.c:103 mutex_destroy+0x84/0x88
>>   DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock))
>>   Modules linked in:
>>   CPU: 0 PID: 12 Comm: kworker/0:1 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>>   Hardware name: Samsung Exynos (Flattened Device Tree)
>>   Workqueue: events deferred_probe_work_func
>>   [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>>   [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>>   [<c0a78178>] (dump_stack) from [<c01271a0>] (__warn+0xf4/0x10c)
>>   [<c01271a0>] (__warn) from [<c012722c>] (warn_slowpath_fmt+0x74/0xb8)
>>   [<c012722c>] (warn_slowpath_fmt) from [<c01892a4>] (mutex_destroy+0x84/0x88)
>>   [<c01892a4>] (mutex_destroy) from [<c05be1a4>] (drm_fb_helper_fini.part.1+0x9c/0xd4)
>>   [<c05be1a4>] (drm_fb_helper_fini.part.1) from [<c05f7464>] (exynos_drm_fbdev_init+0xa0/0xe0)
>>   [<c05f7464>] (exynos_drm_fbdev_init) from [<c05f59f4>] (exynos_drm_bind+0x14c/0x19c)
>>   [<c05f59f4>] (exynos_drm_bind) from [<c0614784>] (try_to_bring_up_master+0x208/0x2bc)
>>   [<c0614784>] (try_to_bring_up_master) from [<c0614ac4>] (__component_add+0xb0/0x178)
>>   [<c0614ac4>] (__component_add) from [<c05fb488>] (exynos_dp_probe+0x94/0x12c)
>>   [<c05fb488>] (exynos_dp_probe) from [<c061e330>] (platform_drv_probe+0x48/0x9c)
>>   [<c061e330>] (platform_drv_probe) from [<c061badc>] (really_probe+0x1c4/0x470)
>>   [<c061badc>] (really_probe) from [<c061bf1c>] (driver_probe_device+0x78/0x1bc)
>>   [<c061bf1c>] (driver_probe_device) from [<c0619c9c>] (bus_for_each_drv+0x74/0xb8)
>>   [<c0619c9c>] (bus_for_each_drv) from [<c061b878>] (__device_attach+0xd4/0x16c)
>>   [<c061b878>] (__device_attach) from [<c061aa38>] (bus_probe_device+0x88/0x90)
>>   [<c061aa38>] (bus_probe_device) from [<c061af5c>] (deferred_probe_work_func+0x4c/0xd0)
>>   [<c061af5c>] (deferred_probe_work_func) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>>   [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>>   [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>>   [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>>   Exception stack(0xee8fdfb0 to 0xee8fdff8)
>>   dfa0:                                     00000000 00000000 00000000 00000000
>>   dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>>   dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>>   irq event stamp: 56283
>>   hardirqs last  enabled at (56283): [<c02b189c>] kfree+0x198/0x3e4
>>   hardirqs last disabled at (56282): [<c02b17d0>] kfree+0xcc/0x3e4
>>   softirqs last  enabled at (56262): [<c0101724>] __do_softirq+0x4fc/0x5f4
>>   softirqs last disabled at (56255): [<c0130248>] irq_exit+0x16c/0x170
>>   ---[ end trace 74519922e0e4625e ]---
>>   exynos-sysmmu 14640000.sysmmu: 14400000.fimd: PAGE FAULT occurred at 0x20000000
>>   ------------[ cut here ]------------
>>   kernel BUG at drivers/iommu/exynos-iommu.c:447!
>>   Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
>>   Modules linked in:
>>   CPU: 0 PID: 52 Comm: kworker/0:2 Tainted: G        W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>>   Hardware name: Samsung Exynos (Flattened Device Tree)
>>   Workqueue: events output_poll_execute
>>   PC is at exynos_sysmmu_irq+0x210/0x258
>>   LR is at report_iommu_fault+0x144/0x1cc
>>   pc : [<c05a6e34>]    lr : [<c05a13ec>]    psr: a0000193
>>   sp : cfafdbe8  ip : 2d495ebb  fp : 00000200
>>   r10: eeb187e0  r9 : 20000000  r8 : cf300000
>>   r7 : c11d4fb0  r6 : eeb187c0  r5 : 00000000  r4 : c0b59f74
>>   r3 : cfafc000  r2 : 00010001  r1 : 00000000  r0 : ffffffda
>>   Flags: NzCv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment none
>>   Control: 10c5387d  Table: 4000406a  DAC: 00000051
>>   Process kworker/0:2 (pid: 52, stack limit = 0x(ptrval))
>>   Stack: (0xcfafdbe8 to 0xcfafe000)
>>   ...
>>   [<c05a6e34>] (exynos_sysmmu_irq) from [<c01a24f4>] (__handle_irq_event_percpu+0x68/0x42c)
>>   [<c01a24f4>] (__handle_irq_event_percpu) from [<c01a28e4>] (handle_irq_event_percpu+0x2c/0x7c)
>>   [<c01a28e4>] (handle_irq_event_percpu) from [<c01a296c>] (handle_irq_event+0x38/0x5c)
>>   [<c01a296c>] (handle_irq_event) from [<c01a7160>] (handle_level_irq+0xcc/0x150)
>>   [<c01a7160>] (handle_level_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
>>   [<c01a1574>] (generic_handle_irq) from [<c0509a5c>] (combiner_handle_cascade_irq+0x8c/0xdc)
>>   [<c0509a5c>] (combiner_handle_cascade_irq) from [<c01a1574>] (generic_handle_irq+0x34/0x44)
>>   [<c01a1574>] (generic_handle_irq) from [<c01a1bbc>] (__handle_domain_irq+0x7c/0xec)
>>   [<c01a1bbc>] (__handle_domain_irq) from [<c050a024>] (gic_handle_irq+0x58/0x9c)
>>   [<c050a024>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
>>   Exception stack(0xcfafdd00 to 0xcfafdd48)
>>   dd00: c02b189c 00000000 2df3c000 00000000 cf2ed3c0 ee801cc0 60000113 ef1ddda0
>>   dd20: c05d5500 00000000 cf2c9800 cf2ea8b8 00003220 cfafdd50 c02b189c c02b18a0
>>   dd40: 60000113 ffffffff
>>   [<c0100af0>] (__irq_svc) from [<c02b18a0>] (kfree+0x19c/0x3e4)
>>   [<c02b18a0>] (kfree) from [<c05d5500>] (drm_atomic_state_default_clear+0x1b8/0x2dc)
>>   [<c05d5500>] (drm_atomic_state_default_clear) from [<c05d5650>] (__drm_atomic_state_free+0x10/0x50)
>>   [<c05d5650>] (__drm_atomic_state_free) from [<c05e9d88>] (drm_client_modeset_commit_atomic+0x240/0x26c)
>>   [<c05e9d88>] (drm_client_modeset_commit_atomic) from [<c05e9df8>] (drm_client_modeset_commit_locked+0x44/0x1d0)
>>   [<c05e9df8>] (drm_client_modeset_commit_locked) from [<c05e9fa8>] (drm_client_modeset_commit+0x24/0x40)
>>   [<c05e9fa8>] (drm_client_modeset_commit) from [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked+0x58/0xa4)
>>   [<c05be3ec>] (drm_fb_helper_restore_fbdev_mode_unlocked) from [<c05be468>] (drm_fb_helper_set_par+0x30/0x5c)
>>   [<c05be468>] (drm_fb_helper_set_par) from [<c05be538>] (drm_fb_helper_hotplug_event.part.5+0xa4/0xbc)
>>   [<c05be538>] (drm_fb_helper_hotplug_event.part.5) from [<c05ac148>] (drm_kms_helper_hotplug_event+0x24/0x30)
>>   [<c05ac148>] (drm_kms_helper_hotplug_event) from [<c05ac238>] (output_poll_execute+0xb8/0x1b4)
>>   [<c05ac238>] (output_poll_execute) from [<c0149f9c>] (process_one_work+0x30c/0x880)
>>   [<c0149f9c>] (process_one_work) from [<c014a568>] (worker_thread+0x58/0x5a4)
>>   [<c014a568>] (worker_thread) from [<c0151a5c>] (kthread+0x154/0x19c)
>>   [<c0151a5c>] (kthread) from [<c0100114>] (ret_from_fork+0x14/0x20)
>>   Exception stack(0xcfafdfb0 to 0xcfafdff8)
>>   dfa0:                                     00000000 00000000 00000000 00000000
>>   dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
>>   dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
>>   Code: e34c00de e300119e ebee00e1 eaffff81 (e7f001f2)
>>   ---[ end trace 74519922e0e4625f ]---
>>   Kernel panic - not syncing: Fatal exception in interrupt
>>   CPU1: stopping
>>   CPU: 1 PID: 0 Comm: swapper/1 Tainted: G      D W         5.6.0-rc7-next-20200326-00060-gbb3f893b3f08 #7929
>>   Hardware name: Samsung Exynos (Flattened Device Tree)
>>   [<c0111f20>] (unwind_backtrace) from [<c010d128>] (show_stack+0x10/0x14)
>>   [<c010d128>] (show_stack) from [<c0a78178>] (dump_stack+0xa4/0xd0)
>>   [<c0a78178>] (dump_stack) from [<c0110ad4>] (handle_IPI+0x3b4/0x440)
>>   [<c0110ad4>] (handle_IPI) from [<c050a064>] (gic_handle_irq+0x98/0x9c)
>>   [<c050a064>] (gic_handle_irq) from [<c0100af0>] (__irq_svc+0x70/0xb0)
>>   Exception stack(0xee8fff58 to 0xee8fffa0)
>>   ff40:                                                       c0109534 00000000
>>   ff60: 2df50000 00000000 ee8fe000 c1108ee8 c1108f2c 00000002 00000000 c0de63c0
>>   ff80: 00000000 c1075fe8 2d495ebb ee8fffa8 c0109534 c0109538 60000013 ffffffff
>>   [<c0100af0>] (__irq_svc) from [<c0109538>] (arch_cpu_idle+0x24/0x44)
>>   [<c0109538>] (arch_cpu_idle) from [<c0163a74>] (do_idle+0x1d8/0x2d4)
>>   [<c0163a74>] (do_idle) from [<c0163f24>] (cpu_startup_entry+0x18/0x1c)
>>   [<c0163f24>] (cpu_startup_entry) from [<401018ac>] (0x401018ac)
>>   ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
>> ---
>>   drivers/gpu/drm/drm_prime.c | 30 ++++++++++++++++++------------
>>   1 file changed, 18 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
>> index 1de2cde2277c..424db18987f6 100644
>> --- a/drivers/gpu/drm/drm_prime.c
>> +++ b/drivers/gpu/drm/drm_prime.c
>> @@ -962,27 +962,33 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
>>          unsigned count;
>>          struct scatterlist *sg;
>>          struct page *page;
>> -       u32 len, index;
>> +       u32 page_len, page_index;
>>          dma_addr_t addr;
>> +       u32 dma_len, dma_index;
>>
>> -       index = 0;
>> +       page_index = 0;
>> +       dma_index = 0;
>>          for_each_sg(sgt->sgl, sg, sgt->nents, count) {
>> -               len = sg_dma_len(sg);
>> +               page_len = sg->length;
>>                  page = sg_page(sg);
>> +               dma_len = sg_dma_len(sg);
>>                  addr = sg_dma_address(sg);
>>
>> -               while (len > 0) {
>> -                       if (WARN_ON(index >= max_entries))
>> +               while (pages && page_len > 0) {
>> +                       if (WARN_ON(page_index >= max_entries))
>>                                  return -1;
>> -                       if (pages)
>> -                               pages[index] = page;
>> -                       if (addrs)
>> -                               addrs[index] = addr;
>> -
>> +                       pages[page_index] = page;
>>                          page++;
>> +                       page_len -= PAGE_SIZE;
>> +                       page_index++;
>> +               }
>> +               while (addrs && dma_len > 0) {
>> +                       if (WARN_ON(dma_index >= max_entries))
>> +                               return -1;
>> +                       addrs[dma_index] = addr;
>>                          addr += PAGE_SIZE;
>> -                       len -= PAGE_SIZE;
>> -                       index++;
>> +                       dma_len -= PAGE_SIZE;
>> +                       dma_index++;
>>                  }
>>          }
>>          return 0;
>> --
>> 2.17.1
>>
> I have tested the above patch against my original issues with amdgpu
> and radeon drivers and everything is still working as expected.
>
> Sorry I missed this in my original patches.

No problem. Thanks for testing!

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Shane Francis]

Hello Marek,

On Fri, Mar 27, 2020 at 9:00 AM Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
> > I have tested the above patch against my original issues with amdgpu
> > and radeon drivers and everything is still working as expected.
> >
> > Sorry I missed this in my original patches.
>
> No problem. Thanks for testing!
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>
Just a thought.

Would it be worth adding some comments to the code to explain why this
is needed, reading
the thread around my original patches and the DMA-API documentation it
is not instantly
clear why you would be mapping the pages in this way.

Would probably prevent someone in the future making the same mistake I
did while updating
this code.

Regards,

Shane Francis

Re: [PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Shane Francis]

Hello Marek,

On Fri, Mar 27, 2020 at 9:00 AM Marek Szyprowski
<m.szyprowski@samsung.com> wrote:
> > I have tested the above patch against my original issues with amdgpu
> > and radeon drivers and everything is still working as expected.
> >
> > Sorry I missed this in my original patches.
>
> No problem. Thanks for testing!
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>
Just a thought.

Would it be worth adding some comments to the code to explain why this
is needed, reading
the thread around my original patches and the DMA-API documentation it
is not instantly
clear why you would be mapping the pages in this way.

Would probably prevent someone in the future making the same mistake I
did while updating
this code.

Regards,

Shane Francis
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel

Re: [PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Alex Deucher]

On Fri, Mar 27, 2020 at 6:25 AM Shane Francis <bigbeeshane@gmail.com> wrote:
>
> Hello Marek,
>
> On Fri, Mar 27, 2020 at 9:00 AM Marek Szyprowski
> <m.szyprowski@samsung.com> wrote:
> > > I have tested the above patch against my original issues with amdgpu
> > > and radeon drivers and everything is still working as expected.
> > >
> > > Sorry I missed this in my original patches.
> >
> > No problem. Thanks for testing!
> >
> > Best regards
> > --
> > Marek Szyprowski, PhD
> > Samsung R&D Institute Poland
> >
> Just a thought.
>
> Would it be worth adding some comments to the code to explain why this
> is needed, reading
> the thread around my original patches and the DMA-API documentation it
> is not instantly
> clear why you would be mapping the pages in this way.
>
> Would probably prevent someone in the future making the same mistake I
> did while updating
> this code.

With a comment similar to the commit messaged added to this function,
this patch is:
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

Thanks!

Alex

Re: [PATCH] drm/prime: fix extracting of the DMA addresses from a scatterlist

[Alex Deucher]

On Fri, Mar 27, 2020 at 6:25 AM Shane Francis <bigbeeshane@gmail.com> wrote:
>
> Hello Marek,
>
> On Fri, Mar 27, 2020 at 9:00 AM Marek Szyprowski
> <m.szyprowski@samsung.com> wrote:
> > > I have tested the above patch against my original issues with amdgpu
> > > and radeon drivers and everything is still working as expected.
> > >
> > > Sorry I missed this in my original patches.
> >
> > No problem. Thanks for testing!
> >
> > Best regards
> > --
> > Marek Szyprowski, PhD
> > Samsung R&D Institute Poland
> >
> Just a thought.
>
> Would it be worth adding some comments to the code to explain why this
> is needed, reading
> the thread around my original patches and the DMA-API documentation it
> is not instantly
> clear why you would be mapping the pages in this way.
>
> Would probably prevent someone in the future making the same mistake I
> did while updating
> this code.

With a comment similar to the commit messaged added to this function,
this patch is:
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

Thanks!

Alex
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