[PATCH v3 0/3] MIPS: Fix some issues about arch_mem_init()

[PATCH v3 0/3] MIPS: Fix some issues about arch_mem_init()

[Tiezhu Yang]

v3:
  - remove the Fixes tag of patch 2/3

v2:
  - modify the subject of patch 3/3

Tiezhu Yang (3):
  MIPS: Do not initialise globals to 0
  MIPS: Cleanup code about plat_mem_setup()
  MIPS: Make sparse_init() using top-down allocation

 arch/mips/include/asm/bootinfo.h |  2 +-
 arch/mips/kernel/setup.c         | 14 +++++++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

-- 
2.1.0

[PATCH v3 1/3] MIPS: Do not initialise globals to 0

[Tiezhu Yang]

Fix the following checkpatch error:

ERROR: do not initialise globals to 0
#834: FILE: arch/mips/kernel/setup.c:834:
+int hw_coherentio = 0;	/* Actual hardware supported DMA coherency setting. */

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---

v3:
  - no changes

v2:
  - no changes

 arch/mips/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 10bef8f..b1e2d43 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -831,7 +831,7 @@ arch_initcall(debugfs_mips);
 /* User defined DMA coherency from command line. */
 enum coherent_io_user_state coherentio = IO_COHERENCE_DEFAULT;
 EXPORT_SYMBOL_GPL(coherentio);
-int hw_coherentio = 0;	/* Actual hardware supported DMA coherency setting. */
+int hw_coherentio;	/* Actual hardware supported DMA coherency setting. */
 
 static int __init setcoherentio(char *str)
 {
-- 
2.1.0

[PATCH v3 2/3] MIPS: Cleanup code about plat_mem_setup()

[Tiezhu Yang]

In the current code, plat_mem_setup() is called by arch_mem_init() instead
of setup_arch() and has been declared in asm/bootinfo.h, so modify the code
comment to reflect the reality and remove the useless duplicate declartion
in arch/mips/kernel/setup.c.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---

v3:
  - remove the Fixes tag

v2:
  - no changes

 arch/mips/include/asm/bootinfo.h | 2 +-
 arch/mips/kernel/setup.c         | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/mips/include/asm/bootinfo.h b/arch/mips/include/asm/bootinfo.h
index 6172778..dcd6a75 100644
--- a/arch/mips/include/asm/bootinfo.h
+++ b/arch/mips/include/asm/bootinfo.h
@@ -121,7 +121,7 @@ extern unsigned long fw_passed_dtb;
 #endif
 
 /*
- * Platform memory detection hook called by setup_arch
+ * Platform memory detection hook called by arch_mem_init()
  */
 extern void plat_mem_setup(void);
 
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index b1e2d43..5481a0c 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -654,8 +654,6 @@ static void __init bootcmdline_init(char **cmdline_p)
  */
 static void __init arch_mem_init(char **cmdline_p)
 {
-	extern void plat_mem_setup(void);
-
 	/* call board setup routine */
 	plat_mem_setup();
 	memblock_set_bottom_up(true);
-- 
2.1.0

[PATCH v3 3/3] MIPS: Make sparse_init() using top-down allocation

[Tiezhu Yang]

In the current code, if CONFIG_SWIOTLB is set, when failed to get IO TLB
memory from the low pages by plat_swiotlb_setup(), it may lead to the boot
process failed with kernel panic.

(1) On the Loongson and SiByte platform
arch/mips/loongson64/dma.c
arch/mips/sibyte/common/dma.c
void __init plat_swiotlb_setup(void)
{
	swiotlb_init(1);
}

kernel/dma/swiotlb.c
void  __init
swiotlb_init(int verbose)
{
...
	vstart = memblock_alloc_low(PAGE_ALIGN(bytes), PAGE_SIZE);
	if (vstart && !swiotlb_init_with_tbl(vstart, io_tlb_nslabs, verbose))
		return;
...
	pr_warn("Cannot allocate buffer");
	no_iotlb_memory = true;
}

phys_addr_t swiotlb_tbl_map_single()
{
...
	if (no_iotlb_memory)
		panic("Can not allocate SWIOTLB buffer earlier ...");
...
}

(2) On the Cavium OCTEON platform
arch/mips/cavium-octeon/dma-octeon.c
void __init plat_swiotlb_setup(void)
{
...
	octeon_swiotlb = memblock_alloc_low(swiotlbsize, PAGE_SIZE);
	if (!octeon_swiotlb)
		panic("%s: Failed to allocate %zu bytes align=%lx\n",
		      __func__, swiotlbsize, PAGE_SIZE);
...
}

Because IO_TLB_DEFAULT_SIZE is 64M, if the rest size of low memory is less
than 64M when call plat_swiotlb_setup(), we can easily reproduce the panic
case.

In order to reduce the possibility of kernel panic when failed to get IO
TLB memory under CONFIG_SWIOTLB, it is better to allocate low memory as
small as possible before plat_swiotlb_setup(), so make sparse_init() using
top-down allocation.

Reported-by: Juxin Gao <gaojuxin@loongson.cn>
Co-developed-by: Juxin Gao <gaojuxin@loongson.cn>
Signed-off-by: Juxin Gao <gaojuxin@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---

v3:
  - no changes

v2:
  - modify the patch subject

 arch/mips/kernel/setup.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 5481a0c..8db533c 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -700,7 +700,17 @@ static void __init arch_mem_init(char **cmdline_p)
 		memblock_reserve(crashk_res.start, resource_size(&crashk_res));
 #endif
 	device_tree_init();
+
+	/*
+	 * In order to reduce the possibility of kernel panic when failed to
+	 * get IO TLB memory under CONFIG_SWIOTLB, it is better to allocate
+	 * low memory as small as possible before plat_swiotlb_setup(), so
+	 * make sparse_init() using top-down allocation.
+	 */
+	memblock_set_bottom_up(false);
 	sparse_init();
+	memblock_set_bottom_up(true);
+
 	plat_swiotlb_setup();
 
 	dma_contiguous_reserve(PFN_PHYS(max_low_pfn));
-- 
2.1.0

Re: [PATCH v3 0/3] MIPS: Fix some issues about arch_mem_init()

[Thomas Bogendoerfer]

On Tue, Apr 21, 2020 at 07:59:43PM +0800, Tiezhu Yang wrote:
> v3:
>   - remove the Fixes tag of patch 2/3
> 
> v2:
>   - modify the subject of patch 3/3
> 
> Tiezhu Yang (3):
>   MIPS: Do not initialise globals to 0
>   MIPS: Cleanup code about plat_mem_setup()
>   MIPS: Make sparse_init() using top-down allocation
> 
>  arch/mips/include/asm/bootinfo.h |  2 +-
>  arch/mips/kernel/setup.c         | 14 +++++++++++---
>  2 files changed, 12 insertions(+), 4 deletions(-)

all three patches applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]