[RFC/PATCH v2 0/8] Clean up write-combining MTRR addition

[RFC/PATCH v2 0/8] Clean up write-combining MTRR addition

[Andy Lutomirski]

A fair number of drivers (mostly graphics) add write-combining MTRRs.
Most ignore errors and most add the MTRR even on PAT systems which don't
need to use MTRRs.

This series adds new functions arch_phys_wc_{add,del} that, on PAT-less
x86 systems with MTRRs, add MTRRs and report errors, and that do nothing
otherwise.  (Other architectures, if any, with a similar mechanism could
implement them.)

I've only tested the radeon driver, since I don't have test hardware
easily available for the other drivers.

Benefits include:
 - Simpler code
 - No more complaints about MTRR conflict warnings on PAT systems
 - Eventual unexporting of the MTRR API?

This series eliminates about half of the mtrr_add calls in drivers/.

Changes from v1:
 - Helpers renamed
 - Lots of bugs fixed

The series is also at:
https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/log/?h=mtrr_cleanup/rfc_v2

Andy Lutomirski (8):
  Add arch_phys_wc_{add,del} to manipulate WC MTRRs if needed
  drm (ast,cirrus,mgag200,nouveau,savage,vmwgfx): Remove
    drm_mtrr_{add,del}
  drm: Update drm_addmap and drm_mmap to use PAT WC instead of MTRRs
  drm,agpgart: Use pgprot_writecombine for AGP maps and make the MTRR
    optional
  i915: Use arch_phys_wc_{add,del}
  radeon: Switch to arch_phys_wc_add and add a missing ..._del
  uvesafb: Clean up MTRR code
  drm: Remove mtrr_add and mtrr_del fallback hack for non-MTRR systems

 Documentation/fb/uvesafb.txt           | 16 +++-----
 arch/x86/include/asm/io.h              |  7 ++++
 arch/x86/include/asm/mtrr.h            |  5 ++-
 arch/x86/kernel/cpu/mtrr/main.c        | 48 +++++++++++++++++++++++
 drivers/char/agp/frontend.c            |  8 ++--
 drivers/gpu/drm/ast/ast_ttm.c          | 13 ++-----
 drivers/gpu/drm/cirrus/cirrus_ttm.c    | 15 ++------
 drivers/gpu/drm/drm_bufs.c             | 17 +++++----
 drivers/gpu/drm/drm_pci.c              |  8 ++--
 drivers/gpu/drm/drm_stub.c             | 10 +----
 drivers/gpu/drm/drm_vm.c               | 22 +++++------
 drivers/gpu/drm/i915/i915_dma.c        | 44 +++------------------
 drivers/gpu/drm/mgag200/mgag200_ttm.c  | 14 ++-----
 drivers/gpu/drm/nouveau/nouveau_ttm.c  | 13 ++-----
 drivers/gpu/drm/radeon/radeon_object.c |  5 ++-
 drivers/gpu/drm/savage/savage_bci.c    | 43 ++++++++-------------
 drivers/gpu/drm/savage/savage_drv.h    |  5 +--
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c    | 10 ++---
 drivers/video/uvesafb.c                | 70 +++++++++-------------------------
 include/drm/drmP.h                     | 34 +----------------
 include/drm/drm_os_linux.h             | 16 --------
 include/linux/io.h                     | 25 ++++++++++++
 include/video/uvesafb.h                |  1 +
 23 files changed, 181 insertions(+), 268 deletions(-)

-- 
1.8.1.4

[RFC/PATCH v2 1/8] Add arch_phys_wc_{add,del} to manipulate WC MTRRs if needed

[Andy Lutomirski]

Several drivers currently use mtrr_add through various #ifdef guards
and/or drm wrappers.  The vast majority of them want to add WC MTRRs
on x86 systems and don't actually need the MTRR if PAT (i.e.
ioremap_wc, etc) are working.

arch_phys_wc_add and arch_phys_wc_del are new functions, available
on all architectures and configurations, that add WC MTRRs on x86 if
needed (and handle errors) and do nothing at all otherwise.  They're
also easier to use than mtrr_add and mtrr_del, so the call sites can
be simplified.

As an added benefit, this will avoid wasting MTRRs and possibly
warning pointlessly on PAT-supporting systems.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
 arch/x86/include/asm/io.h       |  7 ++++++
 arch/x86/include/asm/mtrr.h     |  5 ++++-
 arch/x86/kernel/cpu/mtrr/main.c | 48 +++++++++++++++++++++++++++++++++++++++++
 include/linux/io.h              | 25 +++++++++++++++++++++
 4 files changed, 84 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index d8e8eef..34f69cb 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -345,4 +345,11 @@ extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
 
 #define IO_SPACE_LIMIT 0xffff
 
+#ifdef CONFIG_MTRR
+extern int __must_check arch_phys_wc_add(unsigned long base,
+					 unsigned long size);
+extern void arch_phys_wc_del(int handle);
+#define arch_phys_wc_add arch_phys_wc_add
+#endif
+
 #endif /* _ASM_X86_IO_H */
diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
index e235582..10d0fba 100644
--- a/arch/x86/include/asm/mtrr.h
+++ b/arch/x86/include/asm/mtrr.h
@@ -26,7 +26,10 @@
 #include <uapi/asm/mtrr.h>
 
 
-/*  The following functions are for use by other drivers  */
+/*
+ * The following functions are for use by other drivers that cannot use
+ * arch_phys_wc_add and arch_phys_wc_del.
+ */
 # ifdef CONFIG_MTRR
 extern u8 mtrr_type_lookup(u64 addr, u64 end);
 extern void mtrr_save_fixed_ranges(void *);
diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 726bf96..23bd49a 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -51,6 +51,7 @@
 #include <asm/e820.h>
 #include <asm/mtrr.h>
 #include <asm/msr.h>
+#include <asm/pat.h>
 
 #include "mtrr.h"
 
@@ -524,6 +525,53 @@ int mtrr_del(int reg, unsigned long base, unsigned long size)
 }
 EXPORT_SYMBOL(mtrr_del);
 
+/**
+ * arch_phys_wc_add - add a WC MTRR and handle errors if PAT is unavailable
+ * @base: Physical base address
+ * @size: Size of region
+ *
+ * If PAT is available, this does nothing.  If PAT is unavailable, it
+ * attempts to add a WC MTRR covering size bytes starting at base and
+ * logs an error if this fails.
+ *
+ * Drivers must store the return value to pass to mtrr_del_wc_if_needed,
+ * but drivers should not try to interpret that return value.
+ */
+int arch_phys_wc_add(unsigned long base, unsigned long size)
+{
+	int ret;
+
+	if (pat_enabled)
+		return 0;  /* Success!  (We don't need to do anything.) */
+
+	ret = mtrr_add(base, size, MTRR_TYPE_WRCOMB, true);
+	if (ret < 0) {
+		pr_warn("Failed to add WC MTRR for [%p-%p]; performance may suffer.",
+			(void *)base, (void *)(base + size - 1));
+		return ret;
+	}
+	return ret + 1000;
+}
+EXPORT_SYMBOL(arch_phys_wc_add);
+
+/*
+ * arch_phys_wc_del - undoes arch_phys_wc_add
+ * @handle: Return value from arch_phys_wc_add
+ *
+ * This cleans up after mtrr_add_wc_if_needed.
+ *
+ * The API guarantees that mtrr_del_wc_if_needed(error code) and
+ * mtrr_del_wc_if_needed(0) do nothing.
+ */
+extern void arch_phys_wc_del(int handle)
+{
+	if (handle >= 1) {
+		WARN_ON(handle < 1000);
+		mtrr_del(handle - 1000, 0, 0);
+	}
+}
+EXPORT_SYMBOL(arch_phys_wc_del);
+
 /*
  * HACK ALERT!
  * These should be called implicitly, but we can't yet until all the initcall
diff --git a/include/linux/io.h b/include/linux/io.h
index 069e407..f4f42fa 100644
--- a/include/linux/io.h
+++ b/include/linux/io.h
@@ -76,4 +76,29 @@ void devm_ioremap_release(struct device *dev, void *res);
 #define arch_has_dev_port()     (1)
 #endif
 
+/*
+ * Some systems (x86 without PAT) have a somewhat reliable way to mark a
+ * physical address range such that uncached mappings will actually
+ * end up write-combining.  This facility should be used in conjunction
+ * with pgprot_writecombine, ioremap-wc, or set_memory_wc, since it has
+ * no effect if the per-page mechanisms are functional.
+ * (On x86 without PAT, these functions manipulate MTRRs.)
+ *
+ * arch_phys_del_wc(0) or arch_phys_del_wc(any error code) is guaranteed
+ * to have no effect.
+ */
+#ifndef arch_phys_wc_add
+static inline int __must_check arch_phys_wc_add(unsigned long base,
+						unsigned long size)
+{
+	return 0;  /* It worked (i.e. did nothing). */
+}
+
+static inline void arch_phys_wc_del(int handle)
+{
+}
+
+#define arch_phys_wc_add arch_phys_wc_add
+#endif
+
 #endif /* _LINUX_IO_H */
-- 
1.8.1.4

[RFC/PATCH v2 2/8] drm (ast,cirrus,mgag200,nouveau,savage,vmwgfx): Remove drm_mtrr_{add,del}

[Andy Lutomirski]

This replaces drm_mtrr_{add,del} with arch_phys_wc_{add,del}.  The
interface is simplified (because the base and size parameters to
drm_mtrr_del never did anything), and it no longer adds MTRRs on
systems that don't need them.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
 drivers/gpu/drm/ast/ast_ttm.c         | 13 +++--------
 drivers/gpu/drm/cirrus/cirrus_ttm.c   | 15 ++++--------
 drivers/gpu/drm/mgag200/mgag200_ttm.c | 14 ++++--------
 drivers/gpu/drm/nouveau/nouveau_ttm.c | 13 ++++-------
 drivers/gpu/drm/savage/savage_bci.c   | 43 ++++++++++++-----------------------
 drivers/gpu/drm/savage/savage_drv.h   |  5 +---
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c   | 10 ++++----
 include/drm/drmP.h                    | 29 -----------------------
 8 files changed, 35 insertions(+), 107 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_ttm.c b/drivers/gpu/drm/ast/ast_ttm.c
index 3602731..c4574fd 100644
--- a/drivers/gpu/drm/ast/ast_ttm.c
+++ b/drivers/gpu/drm/ast/ast_ttm.c
@@ -271,26 +271,19 @@ int ast_mm_init(struct ast_private *ast)
 		return ret;
 	}
 
-	ast->fb_mtrr = drm_mtrr_add(pci_resource_start(dev->pdev, 0),
-				    pci_resource_len(dev->pdev, 0),
-				    DRM_MTRR_WC);
+	ast->fb_mtrr = arch_phys_wc_add(pci_resource_start(dev->pdev, 0),
+					pci_resource_len(dev->pdev, 0));
 
 	return 0;
 }
 
 void ast_mm_fini(struct ast_private *ast)
 {
-	struct drm_device *dev = ast->dev;
 	ttm_bo_device_release(&ast->ttm.bdev);
 
 	ast_ttm_global_release(ast);
 
-	if (ast->fb_mtrr >= 0) {
-		drm_mtrr_del(ast->fb_mtrr,
-			     pci_resource_start(dev->pdev, 0),
-			     pci_resource_len(dev->pdev, 0), DRM_MTRR_WC);
-		ast->fb_mtrr = -1;
-	}
+	arch_phys_wc_del(ast->fb_mtrr);
 }
 
 void ast_ttm_placement(struct ast_bo *bo, int domain)
diff --git a/drivers/gpu/drm/cirrus/cirrus_ttm.c b/drivers/gpu/drm/cirrus/cirrus_ttm.c
index 1413a26..09f06d3 100644
--- a/drivers/gpu/drm/cirrus/cirrus_ttm.c
+++ b/drivers/gpu/drm/cirrus/cirrus_ttm.c
@@ -271,9 +271,8 @@ int cirrus_mm_init(struct cirrus_device *cirrus)
 		return ret;
 	}
 
-	cirrus->fb_mtrr = drm_mtrr_add(pci_resource_start(dev->pdev, 0),
-				    pci_resource_len(dev->pdev, 0),
-				    DRM_MTRR_WC);
+	cirrus->fb_mtrr = arch_phys_wc_add(pci_resource_start(dev->pdev, 0),
+					   pci_resource_len(dev->pdev, 0));
 
 	cirrus->mm_inited = true;
 	return 0;
@@ -281,8 +280,6 @@ int cirrus_mm_init(struct cirrus_device *cirrus)
 
 void cirrus_mm_fini(struct cirrus_device *cirrus)
 {
-	struct drm_device *dev = cirrus->dev;
-
 	if (!cirrus->mm_inited)
 		return;
 
@@ -290,12 +287,8 @@ void cirrus_mm_fini(struct cirrus_device *cirrus)
 
 	cirrus_ttm_global_release(cirrus);
 
-	if (cirrus->fb_mtrr >= 0) {
-		drm_mtrr_del(cirrus->fb_mtrr,
-			     pci_resource_start(dev->pdev, 0),
-			     pci_resource_len(dev->pdev, 0), DRM_MTRR_WC);
-		cirrus->fb_mtrr = -1;
-	}
+	arch_phys_wc_del(cirrus->fb_mtrr);
+	cirrus->fb_mtrr = 0;
 }
 
 void cirrus_ttm_placement(struct cirrus_bo *bo, int domain)
diff --git a/drivers/gpu/drm/mgag200/mgag200_ttm.c b/drivers/gpu/drm/mgag200/mgag200_ttm.c
index 8fc9d92..5c6f3c8 100644
--- a/drivers/gpu/drm/mgag200/mgag200_ttm.c
+++ b/drivers/gpu/drm/mgag200/mgag200_ttm.c
@@ -270,26 +270,20 @@ int mgag200_mm_init(struct mga_device *mdev)
 		return ret;
 	}
 
-	mdev->fb_mtrr = drm_mtrr_add(pci_resource_start(dev->pdev, 0),
-				    pci_resource_len(dev->pdev, 0),
-				    DRM_MTRR_WC);
+	mdev->fb_mtrr = arch_phys_wc_add(pci_resource_start(dev->pdev, 0),
+					 pci_resource_len(dev->pdev, 0));
 
 	return 0;
 }
 
 void mgag200_mm_fini(struct mga_device *mdev)
 {
-	struct drm_device *dev = mdev->dev;
 	ttm_bo_device_release(&mdev->ttm.bdev);
 
 	mgag200_ttm_global_release(mdev);
 
-	if (mdev->fb_mtrr >= 0) {
-		drm_mtrr_del(mdev->fb_mtrr,
-			     pci_resource_start(dev->pdev, 0),
-			     pci_resource_len(dev->pdev, 0), DRM_MTRR_WC);
-		mdev->fb_mtrr = -1;
-	}
+	arch_phys_wc_del(mdev->fb_mtrr);
+	mdev->fb_mtrr = 0;
 }
 
 void mgag200_ttm_placement(struct mgag200_bo *bo, int domain)
diff --git a/drivers/gpu/drm/nouveau/nouveau_ttm.c b/drivers/gpu/drm/nouveau/nouveau_ttm.c
index 9be9cb5..63fa6a5 100644
--- a/drivers/gpu/drm/nouveau/nouveau_ttm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_ttm.c
@@ -377,9 +377,8 @@ nouveau_ttm_init(struct nouveau_drm *drm)
 		return ret;
 	}
 
-	drm->ttm.mtrr = drm_mtrr_add(pci_resource_start(dev->pdev, 1),
-				     pci_resource_len(dev->pdev, 1),
-				     DRM_MTRR_WC);
+	drm->ttm.mtrr = arch_phys_wc_add(pci_resource_start(dev->pdev, 1),
+					 pci_resource_len(dev->pdev, 1));
 
 	/* GART init */
 	if (drm->agp.stat != ENABLED) {
@@ -414,10 +413,6 @@ nouveau_ttm_fini(struct nouveau_drm *drm)
 
 	nouveau_ttm_global_release(drm);
 
-	if (drm->ttm.mtrr >= 0) {
-		drm_mtrr_del(drm->ttm.mtrr,
-			     pci_resource_start(drm->dev->pdev, 1),
-			     pci_resource_len(drm->dev->pdev, 1), DRM_MTRR_WC);
-		drm->ttm.mtrr = -1;
-	}
+	arch_phys_wc_del(drm->ttm.mtrr);
+	drm->ttm.mtrr = 0;
 }
diff --git a/drivers/gpu/drm/savage/savage_bci.c b/drivers/gpu/drm/savage/savage_bci.c
index b55c1d6..bd6b2cf 100644
--- a/drivers/gpu/drm/savage/savage_bci.c
+++ b/drivers/gpu/drm/savage/savage_bci.c
@@ -570,9 +570,6 @@ int savage_driver_firstopen(struct drm_device *dev)
 	unsigned int fb_rsrc, aper_rsrc;
 	int ret = 0;
 
-	dev_priv->mtrr[0].handle = -1;
-	dev_priv->mtrr[1].handle = -1;
-	dev_priv->mtrr[2].handle = -1;
 	if (S3_SAVAGE3D_SERIES(dev_priv->chipset)) {
 		fb_rsrc = 0;
 		fb_base = pci_resource_start(dev->pdev, 0);
@@ -584,21 +581,14 @@ int savage_driver_firstopen(struct drm_device *dev)
 		if (pci_resource_len(dev->pdev, 0) == 0x08000000) {
 			/* Don't make MMIO write-cobining! We need 3
 			 * MTRRs. */
-			dev_priv->mtrr[0].base = fb_base;
-			dev_priv->mtrr[0].size = 0x01000000;
-			dev_priv->mtrr[0].handle =
-			    drm_mtrr_add(dev_priv->mtrr[0].base,
-				         dev_priv->mtrr[0].size, DRM_MTRR_WC);
-			dev_priv->mtrr[1].base = fb_base + 0x02000000;
-			dev_priv->mtrr[1].size = 0x02000000;
-			dev_priv->mtrr[1].handle =
-			    drm_mtrr_add(dev_priv->mtrr[1].base,
-					 dev_priv->mtrr[1].size, DRM_MTRR_WC);
-			dev_priv->mtrr[2].base = fb_base + 0x04000000;
-			dev_priv->mtrr[2].size = 0x04000000;
-			dev_priv->mtrr[2].handle =
-			    drm_mtrr_add(dev_priv->mtrr[2].base,
-					 dev_priv->mtrr[2].size, DRM_MTRR_WC);
+			dev_priv->mtrr_handles[0] =
+				arch_phys_wc_add(fb_base, 0x01000000);
+			dev_priv->mtrr_handles[1] =
+				arch_phys_wc_add(fb_base + 0x02000000,
+						 0x02000000);
+			dev_priv->mtrr_handles[2] =
+				arch_phys_wc_add(fb_base + 0x04000000,
+						0x04000000);
 		} else {
 			DRM_ERROR("strange pci_resource_len %08llx\n",
 				  (unsigned long long)
@@ -616,11 +606,9 @@ int savage_driver_firstopen(struct drm_device *dev)
 		if (pci_resource_len(dev->pdev, 1) == 0x08000000) {
 			/* Can use one MTRR to cover both fb and
 			 * aperture. */
-			dev_priv->mtrr[0].base = fb_base;
-			dev_priv->mtrr[0].size = 0x08000000;
-			dev_priv->mtrr[0].handle =
-			    drm_mtrr_add(dev_priv->mtrr[0].base,
-					 dev_priv->mtrr[0].size, DRM_MTRR_WC);
+			dev_priv->mtrr_handles[0] =
+				arch_phys_wc_add(fb_base,
+						 0x08000000);
 		} else {
 			DRM_ERROR("strange pci_resource_len %08llx\n",
 				  (unsigned long long)
@@ -660,11 +648,10 @@ void savage_driver_lastclose(struct drm_device *dev)
 	drm_savage_private_t *dev_priv = dev->dev_private;
 	int i;
 
-	for (i = 0; i < 3; ++i)
-		if (dev_priv->mtrr[i].handle >= 0)
-			drm_mtrr_del(dev_priv->mtrr[i].handle,
-				 dev_priv->mtrr[i].base,
-				 dev_priv->mtrr[i].size, DRM_MTRR_WC);
+	for (i = 0; i < 3; ++i) {
+		arch_phys_wc_del(dev_priv->mtrr_handles[i]);
+		dev_priv->mtrr_handles[i] = 0;
+	}
 }
 
 int savage_driver_unload(struct drm_device *dev)
diff --git a/drivers/gpu/drm/savage/savage_drv.h b/drivers/gpu/drm/savage/savage_drv.h
index df2aac6..c05082a 100644
--- a/drivers/gpu/drm/savage/savage_drv.h
+++ b/drivers/gpu/drm/savage/savage_drv.h
@@ -160,10 +160,7 @@ typedef struct drm_savage_private {
 	drm_local_map_t *cmd_dma;
 	drm_local_map_t fake_dma;
 
-	struct {
-		int handle;
-		unsigned long base, size;
-	} mtrr[3];
+	int mtrr_handles[3];
 
 	/* BCI and status-related stuff */
 	volatile uint32_t *status_ptr, *bci_ptr;
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index 07dfd82..78e2164 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -565,8 +565,8 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
 		dev_priv->has_gmr = false;
 	}
 
-	dev_priv->mmio_mtrr = drm_mtrr_add(dev_priv->mmio_start,
-					   dev_priv->mmio_size, DRM_MTRR_WC);
+	dev_priv->mmio_mtrr = arch_phys_wc_add(dev_priv->mmio_start,
+					       dev_priv->mmio_size);
 
 	dev_priv->mmio_virt = ioremap_wc(dev_priv->mmio_start,
 					 dev_priv->mmio_size);
@@ -664,8 +664,7 @@ out_no_device:
 out_err4:
 	iounmap(dev_priv->mmio_virt);
 out_err3:
-	drm_mtrr_del(dev_priv->mmio_mtrr, dev_priv->mmio_start,
-		     dev_priv->mmio_size, DRM_MTRR_WC);
+	arch_phys_wc_del(dev_priv->mmio_mtrr);
 	if (dev_priv->has_gmr)
 		(void) ttm_bo_clean_mm(&dev_priv->bdev, VMW_PL_GMR);
 	(void)ttm_bo_clean_mm(&dev_priv->bdev, TTM_PL_VRAM);
@@ -709,8 +708,7 @@ static int vmw_driver_unload(struct drm_device *dev)
 
 	ttm_object_device_release(&dev_priv->tdev);
 	iounmap(dev_priv->mmio_virt);
-	drm_mtrr_del(dev_priv->mmio_mtrr, dev_priv->mmio_start,
-		     dev_priv->mmio_size, DRM_MTRR_WC);
+	arch_phys_wc_del(dev_priv->mmio_mtrr);
 	if (dev_priv->has_gmr)
 		(void)ttm_bo_clean_mm(&dev_priv->bdev, VMW_PL_GMR);
 	(void)ttm_bo_clean_mm(&dev_priv->bdev, TTM_PL_VRAM);
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 2d94d74..3e6cfa0 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1249,37 +1249,8 @@ static inline int drm_core_has_MTRR(struct drm_device *dev)
 {
 	return drm_core_check_feature(dev, DRIVER_USE_MTRR);
 }
-
-#define DRM_MTRR_WC		MTRR_TYPE_WRCOMB
-
-static inline int drm_mtrr_add(unsigned long offset, unsigned long size,
-			       unsigned int flags)
-{
-	return mtrr_add(offset, size, flags, 1);
-}
-
-static inline int drm_mtrr_del(int handle, unsigned long offset,
-			       unsigned long size, unsigned int flags)
-{
-	return mtrr_del(handle, offset, size);
-}
-
 #else
 #define drm_core_has_MTRR(dev) (0)
-
-#define DRM_MTRR_WC		0
-
-static inline int drm_mtrr_add(unsigned long offset, unsigned long size,
-			       unsigned int flags)
-{
-	return 0;
-}
-
-static inline int drm_mtrr_del(int handle, unsigned long offset,
-			       unsigned long size, unsigned int flags)
-{
-	return 0;
-}
 #endif
 
 static inline void drm_device_set_unplugged(struct drm_device *dev)
-- 
1.8.1.4

[RFC/PATCH v2 3/8] drm: Update drm_addmap and drm_mmap to use PAT WC instead of MTRRs

[Andy Lutomirski]

Previously, DRM_FRAME_BUFFER mappings, as well as DRM_REGISTERS
mappings with DRM_WRITE_COMBINING set, resulted in an unconditional
MTRR being added but the actual mappings being created as UC-.

Now these mappings have the MTRR added only if needed, but they will
be mapped with pgprot_writecombine.

The non-WC DRM_REGISTERS case now uses pgprot_noncached instead of
hardcoding the bit twiddling.

The DRM_AGP case is unchanged for now.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---

Unlike v1, this should work well even for drivers that call
drmAddMap from userspace.  I didn't understand how the flags were
supposed to work last time around.

 drivers/gpu/drm/drm_bufs.c | 17 +++++++++--------
 drivers/gpu/drm/drm_vm.c   | 23 +++++++++++------------
 2 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c
index 0128147..0190fce 100644
--- a/drivers/gpu/drm/drm_bufs.c
+++ b/drivers/gpu/drm/drm_bufs.c
@@ -210,12 +210,16 @@ static int drm_addmap_core(struct drm_device * dev, resource_size_t offset,
 		if (drm_core_has_MTRR(dev)) {
 			if (map->type == _DRM_FRAME_BUFFER ||
 			    (map->flags & _DRM_WRITE_COMBINING)) {
-				map->mtrr = mtrr_add(map->offset, map->size,
-						     MTRR_TYPE_WRCOMB, 1);
+				map->mtrr =
+					arch_phys_wc_add(map->offset, map->size);
 			}
 		}
 		if (map->type == _DRM_REGISTERS) {
-			map->handle = ioremap(map->offset, map->size);
+			if (map->flags & _DRM_WRITE_COMBINING)
+				map->handle = ioremap_wc(map->offset,
+							 map->size);
+			else
+				map->handle = ioremap(map->offset, map->size);
 			if (!map->handle) {
 				kfree(map);
 				return -ENOMEM;
@@ -451,11 +455,8 @@ int drm_rmmap_locked(struct drm_device *dev, struct drm_local_map *map)
 		iounmap(map->handle);
 		/* FALLTHROUGH */
 	case _DRM_FRAME_BUFFER:
-		if (drm_core_has_MTRR(dev) && map->mtrr >= 0) {
-			int retcode;
-			retcode = mtrr_del(map->mtrr, map->offset, map->size);
-			DRM_DEBUG("mtrr_del=%d\n", retcode);
-		}
+		if (drm_core_has_MTRR(dev))
+			arch_phys_wc_del(map->mtrr);
 		break;
 	case _DRM_SHM:
 		vfree(map->handle);
diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
index db7bd29..163f436 100644
--- a/drivers/gpu/drm/drm_vm.c
+++ b/drivers/gpu/drm/drm_vm.c
@@ -43,14 +43,18 @@
 static void drm_vm_open(struct vm_area_struct *vma);
 static void drm_vm_close(struct vm_area_struct *vma);
 
-static pgprot_t drm_io_prot(uint32_t map_type, struct vm_area_struct *vma)
+static pgprot_t drm_io_prot(struct drm_local_map *map,
+			    struct vm_area_struct *vma)
 {
 	pgprot_t tmp = vm_get_page_prot(vma->vm_flags);
 
 #if defined(__i386__) || defined(__x86_64__)
-	if (boot_cpu_data.x86 > 3 && map_type != _DRM_AGP) {
-		pgprot_val(tmp) |= _PAGE_PCD;
-		pgprot_val(tmp) &= ~_PAGE_PWT;
+	if (map->type != _DRM_AGP) {
+		if (map->type == _DRM_FRAME_BUFFER ||
+		    map->flags & _DRM_WRITE_COMBINING)
+			tmp = pgprot_writecombine(tmp);
+		else
+			tmp = pgprot_noncached(tmp);
 	}
 #elif defined(__powerpc__)
 	pgprot_val(tmp) |= _PAGE_NO_CACHE;
@@ -250,13 +254,8 @@ static void drm_vm_shm_close(struct vm_area_struct *vma)
 			switch (map->type) {
 			case _DRM_REGISTERS:
 			case _DRM_FRAME_BUFFER:
-				if (drm_core_has_MTRR(dev) && map->mtrr >= 0) {
-					int retcode;
-					retcode = mtrr_del(map->mtrr,
-							   map->offset,
-							   map->size);
-					DRM_DEBUG("mtrr_del = %d\n", retcode);
-				}
+				if (drm_core_has_MTRR(dev))
+					arch_phys_wc_del(map->mtrr);
 				iounmap(map->handle);
 				break;
 			case _DRM_SHM:
@@ -617,7 +616,7 @@ int drm_mmap_locked(struct file *filp, struct vm_area_struct *vma)
 	case _DRM_REGISTERS:
 		offset = drm_core_get_reg_ofs(dev);
 		vma->vm_flags |= VM_IO;	/* not in core dump */
-		vma->vm_page_prot = drm_io_prot(map->type, vma);
+		vma->vm_page_prot = drm_io_prot(map, vma);
 		if (io_remap_pfn_range(vma, vma->vm_start,
 				       (map->offset + offset) >> PAGE_SHIFT,
 				       vma->vm_end - vma->vm_start,
-- 
1.8.1.4

[RFC/PATCH v2 4/8] drm,agpgart: Use pgprot_writecombine for AGP maps and make the MTRR optional

[Andy Lutomirski]

I'm not sure I understand the intent of the previous behavior.  mmap
on /dev/agpgart and DRM_AGP maps had no cache flags set, so they
would be fully cacheable.  But the DRM code (most of the time) would
add a write-combining MTRR that would change the effective memory
type to WC.

The new behavior just requests WC explicitly for all AGP maps.

If there is any code out there that expects cacheable access to the
AGP aperture (because the drm driver doesn't request an MTRR or
because it's using /dev/agpgart directly), then it will now end up
with a UC or WC mapping, depending on the architecture and PAT
availability.  But cacheable access to the aperture seems like it's
asking for trouble, because, AIUI, the aperture is an alias of RAM.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---

It's conceivable that libpciaccess could have issues with this due to
memtype conflicts, but I think this is unlikely (as long as a WC
mapping gets there first, I think the conflict resolution rules will
all work out).  In any case, everything that maps the AGP aperture
ought to be using /dev/agpgart or the DRM API, in which case
everything should be okay.

I don't have anything with an AGP slot to test AFAIK.

 drivers/char/agp/frontend.c |  8 +++++---
 drivers/gpu/drm/drm_pci.c   |  8 ++++----
 drivers/gpu/drm/drm_stub.c  | 10 ++--------
 drivers/gpu/drm/drm_vm.c    | 11 ++++-------
 4 files changed, 15 insertions(+), 22 deletions(-)

diff --git a/drivers/char/agp/frontend.c b/drivers/char/agp/frontend.c
index 2e04433..1b19239 100644
--- a/drivers/char/agp/frontend.c
+++ b/drivers/char/agp/frontend.c
@@ -603,7 +603,8 @@ static int agp_mmap(struct file *file, struct vm_area_struct *vma)
 			vma->vm_ops = kerninfo.vm_ops;
 		} else if (io_remap_pfn_range(vma, vma->vm_start,
 				(kerninfo.aper_base + offset) >> PAGE_SHIFT,
-					    size, vma->vm_page_prot)) {
+				size,
+				pgprot_writecombine(vma->vm_page_prot))) {
 			goto out_again;
 		}
 		mutex_unlock(&(agp_fe.agp_mutex));
@@ -618,8 +619,9 @@ static int agp_mmap(struct file *file, struct vm_area_struct *vma)
 		if (kerninfo.vm_ops) {
 			vma->vm_ops = kerninfo.vm_ops;
 		} else if (io_remap_pfn_range(vma, vma->vm_start,
-					    kerninfo.aper_base >> PAGE_SHIFT,
-					    size, vma->vm_page_prot)) {
+				kerninfo.aper_base >> PAGE_SHIFT,
+				size,
+				pgprot_writecombine(vma->vm_page_prot))) {
 			goto out_again;
 		}
 		mutex_unlock(&(agp_fe.agp_mutex));
diff --git a/drivers/gpu/drm/drm_pci.c b/drivers/gpu/drm/drm_pci.c
index bd719e9..d0f6699 100644
--- a/drivers/gpu/drm/drm_pci.c
+++ b/drivers/gpu/drm/drm_pci.c
@@ -278,10 +278,10 @@ int drm_pci_agp_init(struct drm_device *dev)
 		}
 		if (drm_core_has_MTRR(dev)) {
 			if (dev->agp)
-				dev->agp->agp_mtrr =
-					mtrr_add(dev->agp->agp_info.aper_base,
-						 dev->agp->agp_info.aper_size *
-						 1024 * 1024, MTRR_TYPE_WRCOMB, 1);
+				dev->agp->agp_mtrr = arch_phys_wc_add(
+					dev->agp->agp_info.aper_base,
+					dev->agp->agp_info.aper_size *
+					1024 * 1024);
 		}
 	}
 	return 0;
diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index 7d30802..9e2acdf 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -451,14 +451,8 @@ void drm_put_dev(struct drm_device *dev)
 
 	drm_lastclose(dev);
 
-	if (drm_core_has_MTRR(dev) && drm_core_has_AGP(dev) &&
-	    dev->agp && dev->agp->agp_mtrr >= 0) {
-		int retval;
-		retval = mtrr_del(dev->agp->agp_mtrr,
-				  dev->agp->agp_info.aper_base,
-				  dev->agp->agp_info.aper_size * 1024 * 1024);
-		DRM_DEBUG("mtrr_del=%d\n", retval);
-	}
+	if (drm_core_has_MTRR(dev) && drm_core_has_AGP(dev) && dev->agp)
+		arch_phys_wc_del(dev->agp->agp_mtrr);
 
 	if (dev->driver->unload)
 		dev->driver->unload(dev);
diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
index 163f436..b1e4ec8 100644
--- a/drivers/gpu/drm/drm_vm.c
+++ b/drivers/gpu/drm/drm_vm.c
@@ -49,13 +49,10 @@ static pgprot_t drm_io_prot(struct drm_local_map *map,
 	pgprot_t tmp = vm_get_page_prot(vma->vm_flags);
 
 #if defined(__i386__) || defined(__x86_64__)
-	if (map->type != _DRM_AGP) {
-		if (map->type == _DRM_FRAME_BUFFER ||
-		    map->flags & _DRM_WRITE_COMBINING)
-			tmp = pgprot_writecombine(tmp);
-		else
-			tmp = pgprot_noncached(tmp);
-	}
+	if (map->type == _DRM_REGISTERS && !(map->flags & _DRM_WRITE_COMBINING))
+		tmp = pgprot_noncached(tmp);
+	else
+		tmp = pgprot_writecombine(tmp);
 #elif defined(__powerpc__)
 	pgprot_val(tmp) |= _PAGE_NO_CACHE;
 	if (map_type == _DRM_REGISTERS)
-- 
1.8.1.4

[RFC/PATCH v2 5/8] i915: Use arch_phys_wc_{add,del}

[Andy Lutomirski]

i915 open-coded logic that was essentially equivalent to the new API.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---

Changes from v1: More cleanup

 drivers/gpu/drm/i915/i915_dma.c | 44 ++++++-----------------------------------
 1 file changed, 6 insertions(+), 38 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 4fa6beb..cfdfb45 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -42,7 +42,6 @@
 #include <linux/vga_switcheroo.h>
 #include <linux/slab.h>
 #include <acpi/video.h>
-#include <asm/pat.h>
 
 #define LP_RING(d) (&((struct drm_i915_private *)(d))->ring[RCS])
 
@@ -1393,29 +1392,6 @@ void i915_master_destroy(struct drm_device *dev, struct drm_master *master)
 	master->driver_priv = NULL;
 }
 
-static void
-i915_mtrr_setup(struct drm_i915_private *dev_priv, unsigned long base,
-		unsigned long size)
-{
-	dev_priv->mm.gtt_mtrr = -1;
-
-#if defined(CONFIG_X86_PAT)
-	if (cpu_has_pat)
-		return;
-#endif
-
-	/* Set up a WC MTRR for non-PAT systems.  This is more common than
-	 * one would think, because the kernel disables PAT on first
-	 * generation Core chips because WC PAT gets overridden by a UC
-	 * MTRR if present.  Even if a UC MTRR isn't present.
-	 */
-	dev_priv->mm.gtt_mtrr = mtrr_add(base, size, MTRR_TYPE_WRCOMB, 1);
-	if (dev_priv->mm.gtt_mtrr < 0) {
-		DRM_INFO("MTRR allocation failed.  Graphics "
-			 "performance may suffer.\n");
-	}
-}
-
 static void i915_kick_out_firmware_fb(struct drm_i915_private *dev_priv)
 {
 	struct apertures_struct *ap;
@@ -1552,8 +1528,8 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 		goto out_rmmap;
 	}
 
-	i915_mtrr_setup(dev_priv, dev_priv->gtt.mappable_base,
-			aperture_size);
+	dev_priv->mm.gtt_mtrr = arch_phys_wc_add(dev_priv->gtt.mappable_base,
+						 aperture_size);
 
 	/* The i915 workqueue is primarily used for batched retirement of
 	 * requests (and thus managing bo) once the task has been completed
@@ -1656,12 +1632,8 @@ out_gem_unload:
 	intel_teardown_mchbar(dev);
 	destroy_workqueue(dev_priv->wq);
 out_mtrrfree:
-	if (dev_priv->mm.gtt_mtrr >= 0) {
-		mtrr_del(dev_priv->mm.gtt_mtrr,
-			 dev_priv->gtt.mappable_base,
-			 aperture_size);
-		dev_priv->mm.gtt_mtrr = -1;
-	}
+	arch_phys_wc_del(dev_priv->mm.gtt_mtrr);
+	dev_priv->mm.gtt_mtrr = 0;
 	io_mapping_free(dev_priv->gtt.mappable);
 out_rmmap:
 	pci_iounmap(dev->pdev, dev_priv->regs);
@@ -1697,12 +1669,8 @@ int i915_driver_unload(struct drm_device *dev)
 	cancel_delayed_work_sync(&dev_priv->mm.retire_work);
 
 	io_mapping_free(dev_priv->gtt.mappable);
-	if (dev_priv->mm.gtt_mtrr >= 0) {
-		mtrr_del(dev_priv->mm.gtt_mtrr,
-			 dev_priv->gtt.mappable_base,
-			 dev_priv->gtt.mappable_end);
-		dev_priv->mm.gtt_mtrr = -1;
-	}
+	arch_phys_wc_del(dev_priv->mm.gtt_mtrr);
+	dev_priv->mm.gtt_mtrr = 0;
 
 	acpi_video_unregister();
 
-- 
1.8.1.4

[RFC/PATCH v2 6/8] radeon: Switch to arch_phys_wc_add and add a missing ..._del

[Andy Lutomirski]

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
 drivers/gpu/drm/radeon/radeon_object.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index d3aface..15cd34b 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -321,8 +321,8 @@ void radeon_bo_force_delete(struct radeon_device *rdev)
 int radeon_bo_init(struct radeon_device *rdev)
 {
 	/* Add an MTRR for the VRAM */
-	rdev->mc.vram_mtrr = mtrr_add(rdev->mc.aper_base, rdev->mc.aper_size,
-			MTRR_TYPE_WRCOMB, 1);
+	rdev->mc.vram_mtrr = arch_phys_wc_add(rdev->mc.aper_base,
+					      rdev->mc.aper_size);
 	DRM_INFO("Detected VRAM RAM=%lluM, BAR=%lluM\n",
 		rdev->mc.mc_vram_size >> 20,
 		(unsigned long long)rdev->mc.aper_size >> 20);
@@ -334,6 +334,7 @@ int radeon_bo_init(struct radeon_device *rdev)
 void radeon_bo_fini(struct radeon_device *rdev)
 {
 	radeon_ttm_fini(rdev);
+	arch_phys_wc_del(rdev->mc.vram_mtrr);
 }
 
 void radeon_bo_list_add_object(struct radeon_bo_list *lobj,
-- 
1.8.1.4

[RFC/PATCH v2 7/8] uvesafb: Clean up MTRR code

[Andy Lutomirski]

The old code allowed very strange memory types.  Now it works like
all the other video drivers: ioremap_wc is used unconditionally,
and MTRRs are set if PAT is unavailable (unless MTRR is disabled
by a module parameter).

UC, WB, and WT support is gone.  If there are MTRR conflicts that prevent
addition of a WC MTRR, adding a non-conflicting MTRR is pointless; it's
better to just turn off MTRR support entirely.

As an added bonus, any MTRR added is freed on unload.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
 Documentation/fb/uvesafb.txt | 16 ++++------
 drivers/video/uvesafb.c      | 70 +++++++++++---------------------------------
 include/video/uvesafb.h      |  1 +
 3 files changed, 23 insertions(+), 64 deletions(-)

diff --git a/Documentation/fb/uvesafb.txt b/Documentation/fb/uvesafb.txt
index eefdd91..f6362d8 100644
--- a/Documentation/fb/uvesafb.txt
+++ b/Documentation/fb/uvesafb.txt
@@ -81,17 +81,11 @@ pmipal  Use the protected mode interface for palette changes.
 
 mtrr:n  Setup memory type range registers for the framebuffer
         where n:
-              0 - disabled (equivalent to nomtrr) (default)
-              1 - uncachable
-              2 - write-back
-              3 - write-combining
-              4 - write-through
-
-        If you see the following in dmesg, choose the type that matches
-        the old one.  In this example, use "mtrr:2".
-...
-mtrr: type mismatch for e0000000,8000000 old: write-back new: write-combining
-...
+              0 - disabled (equivalent to nomtrr)
+              3 - write-combining (default)
+
+	Values other than 0 and 3 will result in a warning and will be
+	treated just like 3.
 
 nomtrr  Do not use memory type range registers.
 
diff --git a/drivers/video/uvesafb.c b/drivers/video/uvesafb.c
index d428445..8701f96 100644
--- a/drivers/video/uvesafb.c
+++ b/drivers/video/uvesafb.c
@@ -24,9 +24,6 @@
 #ifdef CONFIG_X86
 #include <video/vga.h>
 #endif
-#ifdef CONFIG_MTRR
-#include <asm/mtrr.h>
-#endif
 #include "edid.h"
 
 static struct cb_id uvesafb_cn_id = {
@@ -1540,67 +1537,30 @@ static void uvesafb_init_info(struct fb_info *info, struct vbe_mode_ib *mode)
 
 static void uvesafb_init_mtrr(struct fb_info *info)
 {
-#ifdef CONFIG_MTRR
+	struct uvesafb_par *par = info->par;
+
 	if (mtrr && !(info->fix.smem_start & (PAGE_SIZE - 1))) {
 		int temp_size = info->fix.smem_len;
-		unsigned int type = 0;
 
-		switch (mtrr) {
-		case 1:
-			type = MTRR_TYPE_UNCACHABLE;
-			break;
-		case 2:
-			type = MTRR_TYPE_WRBACK;
-			break;
-		case 3:
-			type = MTRR_TYPE_WRCOMB;
-			break;
-		case 4:
-			type = MTRR_TYPE_WRTHROUGH;
-			break;
-		default:
-			type = 0;
-			break;
-		}
+		int rc;
 
-		if (type) {
-			int rc;
+		/* Find the largest power-of-two */
+		temp_size = roundup_pow_of_two(temp_size);
 
-			/* Find the largest power-of-two */
-			temp_size = roundup_pow_of_two(temp_size);
+		/* Try and find a power of two to add */
+		do {
+			rc = arch_phys_wc_add(info->fix.smem_start, temp_size);
+			temp_size >>= 1;
+		} while (temp_size >= PAGE_SIZE && rc == -EINVAL);
 
-			/* Try and find a power of two to add */
-			do {
-				rc = mtrr_add(info->fix.smem_start,
-					      temp_size, type, 1);
-				temp_size >>= 1;
-			} while (temp_size >= PAGE_SIZE && rc == -EINVAL);
-		}
+		if (rc >= 0)
+			par->mtrr_handle = rc;
 	}
-#endif /* CONFIG_MTRR */
 }
 
 static void uvesafb_ioremap(struct fb_info *info)
 {
-#ifdef CONFIG_X86
-	switch (mtrr) {
-	case 1: /* uncachable */
-		info->screen_base = ioremap_nocache(info->fix.smem_start, info->fix.smem_len);
-		break;
-	case 2: /* write-back */
-		info->screen_base = ioremap_cache(info->fix.smem_start, info->fix.smem_len);
-		break;
-	case 3: /* write-combining */
-		info->screen_base = ioremap_wc(info->fix.smem_start, info->fix.smem_len);
-		break;
-	case 4: /* write-through */
-	default:
-		info->screen_base = ioremap(info->fix.smem_start, info->fix.smem_len);
-		break;
-	}
-#else
-	info->screen_base = ioremap(info->fix.smem_start, info->fix.smem_len);
-#endif /* CONFIG_X86 */
+	info->screen_base = ioremap_wc(info->fix.smem_start, info->fix.smem_len);
 }
 
 static ssize_t uvesafb_show_vbe_ver(struct device *dev,
@@ -1851,6 +1811,7 @@ static int uvesafb_remove(struct platform_device *dev)
 		unregister_framebuffer(info);
 		release_region(0x3c0, 32);
 		iounmap(info->screen_base);
+		arch_phys_wc_del(par->mtrr_handle);
 		release_mem_region(info->fix.smem_start, info->fix.smem_len);
 		fb_destroy_modedb(info->monspecs.modedb);
 		fb_dealloc_cmap(&info->cmap);
@@ -1930,6 +1891,9 @@ static int uvesafb_setup(char *options)
 		}
 	}
 
+	if (mtrr != 3 && mtrr != 1)
+		pr_warn("uvesafb: mtrr should be set to 0 or 3; %d is unsupported", mtrr);
+
 	return 0;
 }
 #endif /* !MODULE */
diff --git a/include/video/uvesafb.h b/include/video/uvesafb.h
index 1a91850..30f5362 100644
--- a/include/video/uvesafb.h
+++ b/include/video/uvesafb.h
@@ -134,6 +134,7 @@ struct uvesafb_par {
 
 	int mode_idx;
 	struct vbe_crtc_ib crtc;
+	int mtrr_handle;
 };
 
 #endif /* _UVESAFB_H */
-- 
1.8.1.4

[RFC/PATCH v2 8/8] drm: Remove mtrr_add and mtrr_del fallback hack for non-MTRR systems

[Andy Lutomirski]

There are no users left in drivers/gpu.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---

This is new in v2.  The code I'm deleting is kind of gross.

 include/drm/drmP.h         |  5 +----
 include/drm/drm_os_linux.h | 16 ----------------
 2 files changed, 1 insertion(+), 20 deletions(-)

diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 3e6cfa0..7a9fef5 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -55,16 +55,13 @@
 #include <linux/mm.h>
 #include <linux/cdev.h>
 #include <linux/mutex.h>
+#include <linux/io.h>
 #include <linux/slab.h>
 #if defined(__alpha__) || defined(__powerpc__)
 #include <asm/pgtable.h>	/* For pte_wrprotect */
 #endif
-#include <asm/io.h>
 #include <asm/mman.h>
 #include <asm/uaccess.h>
-#ifdef CONFIG_MTRR
-#include <asm/mtrr.h>
-#endif
 #if defined(CONFIG_AGP) || defined(CONFIG_AGP_MODULE)
 #include <linux/types.h>
 #include <linux/agp_backend.h>
diff --git a/include/drm/drm_os_linux.h b/include/drm/drm_os_linux.h
index 3933691..35c7c2b 100644
--- a/include/drm/drm_os_linux.h
+++ b/include/drm/drm_os_linux.h
@@ -65,22 +65,6 @@ struct no_agp_kern {
 #define DRM_AGP_KERN            struct no_agp_kern
 #endif
 
-#if !(__OS_HAS_MTRR)
-static __inline__ int mtrr_add(unsigned long base, unsigned long size,
-			       unsigned int type, char increment)
-{
-	return -ENODEV;
-}
-
-static __inline__ int mtrr_del(int reg, unsigned long base, unsigned long size)
-{
-	return -ENODEV;
-}
-
-#define MTRR_TYPE_WRCOMB     1
-
-#endif
-
 /** Other copying of data to kernel space */
 #define DRM_COPY_FROM_USER(arg1, arg2, arg3)		\
 	copy_from_user(arg1, arg2, arg3)
-- 
1.8.1.4

Re: [RFC/PATCH v2 0/8] Clean up write-combining MTRR addition

[Jerome Glisse]

On Thu, May 9, 2013 at 3:46 PM, Andy Lutomirski <luto@amacapital.net> wrote:
> A fair number of drivers (mostly graphics) add write-combining MTRRs.
> Most ignore errors and most add the MTRR even on PAT systems which don't
> need to use MTRRs.

This comment is wrong, as i said we need MTRR on PAT system for VRAM.

Cheers,
Jerome

> This series adds new functions arch_phys_wc_{add,del} that, on PAT-less
> x86 systems with MTRRs, add MTRRs and report errors, and that do nothing
> otherwise.  (Other architectures, if any, with a similar mechanism could
> implement them.)
>
> I've only tested the radeon driver, since I don't have test hardware
> easily available for the other drivers.
>
> Benefits include:
>  - Simpler code
>  - No more complaints about MTRR conflict warnings on PAT systems
>  - Eventual unexporting of the MTRR API?
>
> This series eliminates about half of the mtrr_add calls in drivers/.
>
> Changes from v1:
>  - Helpers renamed
>  - Lots of bugs fixed
>
> The series is also at:
> https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/log/?h=mtrr_cleanup/rfc_v2
>
> Andy Lutomirski (8):
>   Add arch_phys_wc_{add,del} to manipulate WC MTRRs if needed
>   drm (ast,cirrus,mgag200,nouveau,savage,vmwgfx): Remove
>     drm_mtrr_{add,del}
>   drm: Update drm_addmap and drm_mmap to use PAT WC instead of MTRRs
>   drm,agpgart: Use pgprot_writecombine for AGP maps and make the MTRR
>     optional
>   i915: Use arch_phys_wc_{add,del}
>   radeon: Switch to arch_phys_wc_add and add a missing ..._del
>   uvesafb: Clean up MTRR code
>   drm: Remove mtrr_add and mtrr_del fallback hack for non-MTRR systems
>
>  Documentation/fb/uvesafb.txt           | 16 +++-----
>  arch/x86/include/asm/io.h              |  7 ++++
>  arch/x86/include/asm/mtrr.h            |  5 ++-
>  arch/x86/kernel/cpu/mtrr/main.c        | 48 +++++++++++++++++++++++
>  drivers/char/agp/frontend.c            |  8 ++--
>  drivers/gpu/drm/ast/ast_ttm.c          | 13 ++-----
>  drivers/gpu/drm/cirrus/cirrus_ttm.c    | 15 ++------
>  drivers/gpu/drm/drm_bufs.c             | 17 +++++----
>  drivers/gpu/drm/drm_pci.c              |  8 ++--
>  drivers/gpu/drm/drm_stub.c             | 10 +----
>  drivers/gpu/drm/drm_vm.c               | 22 +++++------
>  drivers/gpu/drm/i915/i915_dma.c        | 44 +++------------------
>  drivers/gpu/drm/mgag200/mgag200_ttm.c  | 14 ++-----
>  drivers/gpu/drm/nouveau/nouveau_ttm.c  | 13 ++-----
>  drivers/gpu/drm/radeon/radeon_object.c |  5 ++-
>  drivers/gpu/drm/savage/savage_bci.c    | 43 ++++++++-------------
>  drivers/gpu/drm/savage/savage_drv.h    |  5 +--
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c    | 10 ++---
>  drivers/video/uvesafb.c                | 70 +++++++++-------------------------
>  include/drm/drmP.h                     | 34 +----------------
>  include/drm/drm_os_linux.h             | 16 --------
>  include/linux/io.h                     | 25 ++++++++++++
>  include/video/uvesafb.h                |  1 +
>  23 files changed, 181 insertions(+), 268 deletions(-)
>
> --
> 1.8.1.4
>

Re: [RFC/PATCH v2 0/8] Clean up write-combining MTRR addition

[Andy Lutomirski]

On Thu, May 9, 2013 at 4:44 PM, Jerome Glisse <j.glisse@gmail.com> wrote:
> On Thu, May 9, 2013 at 3:46 PM, Andy Lutomirski <luto@amacapital.net> wrote:
>> A fair number of drivers (mostly graphics) add write-combining MTRRs.
>> Most ignore errors and most add the MTRR even on PAT systems which don't
>> need to use MTRRs.
>
> This comment is wrong, as i said we need MTRR on PAT system for VRAM.

I didn't follow it last time.

 - If userspace is setting an MTRR directly, then it will work exactly
as before -- this patch has no effect on the userspace MTRR APIs.

 - If userspace uses the drm map interface with DRM_FRAME_BUFFER or
DRM_WRITE_COMBINING, there won't be an MTRR but the range will still
be WC.

 - If userspace uses GEM or TTM, then everything should still use WC
(TTM has explicit handling for this, which I presume is correct, and
i915, the major GEM user, already doesn't set an MTRR).

 - If userspace does not map the range, then either the kernel driver
is buggy or it doesn't matter because there's no map.

Is there a case I've missed?

--Andy

Re: [RFC/PATCH v2 1/8] Add arch_phys_wc_{add,del} to manipulate WC MTRRs if needed

[Daniel Vetter]

On Thu, May 09, 2013 at 12:46:20PM -0700, Andy Lutomirski wrote:
> Several drivers currently use mtrr_add through various #ifdef guards
> and/or drm wrappers.  The vast majority of them want to add WC MTRRs
> on x86 systems and don't actually need the MTRR if PAT (i.e.
> ioremap_wc, etc) are working.
> 
> arch_phys_wc_add and arch_phys_wc_del are new functions, available
> on all architectures and configurations, that add WC MTRRs on x86 if
> needed (and handle errors) and do nothing at all otherwise.  They're
> also easier to use than mtrr_add and mtrr_del, so the call sites can
> be simplified.
> 
> As an added benefit, this will avoid wasting MTRRs and possibly
> warning pointlessly on PAT-supporting systems.
> 
> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
> ---
>  arch/x86/include/asm/io.h       |  7 ++++++
>  arch/x86/include/asm/mtrr.h     |  5 ++++-
>  arch/x86/kernel/cpu/mtrr/main.c | 48 +++++++++++++++++++++++++++++++++++++++++
>  include/linux/io.h              | 25 +++++++++++++++++++++
>  4 files changed, 84 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
> index d8e8eef..34f69cb 100644
> --- a/arch/x86/include/asm/io.h
> +++ b/arch/x86/include/asm/io.h
> @@ -345,4 +345,11 @@ extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
>  
>  #define IO_SPACE_LIMIT 0xffff
>  
> +#ifdef CONFIG_MTRR
> +extern int __must_check arch_phys_wc_add(unsigned long base,
> +					 unsigned long size);
> +extern void arch_phys_wc_del(int handle);
> +#define arch_phys_wc_add arch_phys_wc_add
> +#endif
> +
>  #endif /* _ASM_X86_IO_H */
> diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
> index e235582..10d0fba 100644
> --- a/arch/x86/include/asm/mtrr.h
> +++ b/arch/x86/include/asm/mtrr.h
> @@ -26,7 +26,10 @@
>  #include <uapi/asm/mtrr.h>
>  
>  
> -/*  The following functions are for use by other drivers  */
> +/*
> + * The following functions are for use by other drivers that cannot use
> + * arch_phys_wc_add and arch_phys_wc_del.
> + */
>  # ifdef CONFIG_MTRR
>  extern u8 mtrr_type_lookup(u64 addr, u64 end);
>  extern void mtrr_save_fixed_ranges(void *);
> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> index 726bf96..23bd49a 100644
> --- a/arch/x86/kernel/cpu/mtrr/main.c
> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> @@ -51,6 +51,7 @@
>  #include <asm/e820.h>
>  #include <asm/mtrr.h>
>  #include <asm/msr.h>
> +#include <asm/pat.h>
>  
>  #include "mtrr.h"
>  
> @@ -524,6 +525,53 @@ int mtrr_del(int reg, unsigned long base, unsigned long size)
>  }
>  EXPORT_SYMBOL(mtrr_del);
>  
> +/**
> + * arch_phys_wc_add - add a WC MTRR and handle errors if PAT is unavailable
> + * @base: Physical base address
> + * @size: Size of region
> + *
> + * If PAT is available, this does nothing.  If PAT is unavailable, it
> + * attempts to add a WC MTRR covering size bytes starting at base and
> + * logs an error if this fails.
> + *
> + * Drivers must store the return value to pass to mtrr_del_wc_if_needed,
> + * but drivers should not try to interpret that return value.
> + */
> +int arch_phys_wc_add(unsigned long base, unsigned long size)
> +{
> +	int ret;
> +
> +	if (pat_enabled)
> +		return 0;  /* Success!  (We don't need to do anything.) */

Shouldn't we #define a big number for this case since mtrr_add returns
0-based mtrr indices? Rather unlikely that the very first mtrr is unused I
know, but still feels like a cleaner interface. And we don't need to leak
that #define out at all to users of this interface.
-Daniel

> +
> +	ret = mtrr_add(base, size, MTRR_TYPE_WRCOMB, true);
> +	if (ret < 0) {
> +		pr_warn("Failed to add WC MTRR for [%p-%p]; performance may suffer.",
> +			(void *)base, (void *)(base + size - 1));
> +		return ret;
> +	}
> +	return ret + 1000;
> +}
> +EXPORT_SYMBOL(arch_phys_wc_add);
> +
> +/*
> + * arch_phys_wc_del - undoes arch_phys_wc_add
> + * @handle: Return value from arch_phys_wc_add
> + *
> + * This cleans up after mtrr_add_wc_if_needed.
> + *
> + * The API guarantees that mtrr_del_wc_if_needed(error code) and
> + * mtrr_del_wc_if_needed(0) do nothing.
> + */
> +extern void arch_phys_wc_del(int handle)
> +{
> +	if (handle >= 1) {
> +		WARN_ON(handle < 1000);
> +		mtrr_del(handle - 1000, 0, 0);
> +	}
> +}
> +EXPORT_SYMBOL(arch_phys_wc_del);
> +
>  /*
>   * HACK ALERT!
>   * These should be called implicitly, but we can't yet until all the initcall
> diff --git a/include/linux/io.h b/include/linux/io.h
> index 069e407..f4f42fa 100644
> --- a/include/linux/io.h
> +++ b/include/linux/io.h
> @@ -76,4 +76,29 @@ void devm_ioremap_release(struct device *dev, void *res);
>  #define arch_has_dev_port()     (1)
>  #endif
>  
> +/*
> + * Some systems (x86 without PAT) have a somewhat reliable way to mark a
> + * physical address range such that uncached mappings will actually
> + * end up write-combining.  This facility should be used in conjunction
> + * with pgprot_writecombine, ioremap-wc, or set_memory_wc, since it has
> + * no effect if the per-page mechanisms are functional.
> + * (On x86 without PAT, these functions manipulate MTRRs.)
> + *
> + * arch_phys_del_wc(0) or arch_phys_del_wc(any error code) is guaranteed
> + * to have no effect.
> + */
> +#ifndef arch_phys_wc_add
> +static inline int __must_check arch_phys_wc_add(unsigned long base,
> +						unsigned long size)
> +{
> +	return 0;  /* It worked (i.e. did nothing). */
> +}
> +
> +static inline void arch_phys_wc_del(int handle)
> +{
> +}
> +
> +#define arch_phys_wc_add arch_phys_wc_add
> +#endif
> +
>  #endif /* _LINUX_IO_H */
> -- 
> 1.8.1.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC/PATCH v2 5/8] i915: Use arch_phys_wc_{add,del}

[Daniel Vetter]

On Thu, May 09, 2013 at 12:46:24PM -0700, Andy Lutomirski wrote:
> i915 open-coded logic that was essentially equivalent to the new API.
> 
> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
> ---
> 
> Changes from v1: More cleanup
> 
>  drivers/gpu/drm/i915/i915_dma.c | 44 ++++++-----------------------------------
>  1 file changed, 6 insertions(+), 38 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 4fa6beb..cfdfb45 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -42,7 +42,6 @@
>  #include <linux/vga_switcheroo.h>
>  #include <linux/slab.h>
>  #include <acpi/video.h>
> -#include <asm/pat.h>
>  
>  #define LP_RING(d) (&((struct drm_i915_private *)(d))->ring[RCS])
>  
> @@ -1393,29 +1392,6 @@ void i915_master_destroy(struct drm_device *dev, struct drm_master *master)
>  	master->driver_priv = NULL;
>  }
>  
> -static void
> -i915_mtrr_setup(struct drm_i915_private *dev_priv, unsigned long base,
> -		unsigned long size)
> -{
> -	dev_priv->mm.gtt_mtrr = -1;
> -
> -#if defined(CONFIG_X86_PAT)
> -	if (cpu_has_pat)
> -		return;
> -#endif
> -
> -	/* Set up a WC MTRR for non-PAT systems.  This is more common than
> -	 * one would think, because the kernel disables PAT on first
> -	 * generation Core chips because WC PAT gets overridden by a UC
> -	 * MTRR if present.  Even if a UC MTRR isn't present.
> -	 */
> -	dev_priv->mm.gtt_mtrr = mtrr_add(base, size, MTRR_TYPE_WRCOMB, 1);
> -	if (dev_priv->mm.gtt_mtrr < 0) {
> -		DRM_INFO("MTRR allocation failed.  Graphics "
> -			 "performance may suffer.\n");
> -	}
> -}
> -
>  static void i915_kick_out_firmware_fb(struct drm_i915_private *dev_priv)
>  {
>  	struct apertures_struct *ap;
> @@ -1552,8 +1528,8 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
>  		goto out_rmmap;
>  	}
>  
> -	i915_mtrr_setup(dev_priv, dev_priv->gtt.mappable_base,
> -			aperture_size);
> +	dev_priv->mm.gtt_mtrr = arch_phys_wc_add(dev_priv->gtt.mappable_base,
> +						 aperture_size);
>  
>  	/* The i915 workqueue is primarily used for batched retirement of
>  	 * requests (and thus managing bo) once the task has been completed
> @@ -1656,12 +1632,8 @@ out_gem_unload:
>  	intel_teardown_mchbar(dev);
>  	destroy_workqueue(dev_priv->wq);
>  out_mtrrfree:
> -	if (dev_priv->mm.gtt_mtrr >= 0) {
> -		mtrr_del(dev_priv->mm.gtt_mtrr,
> -			 dev_priv->gtt.mappable_base,
> -			 aperture_size);
> -		dev_priv->mm.gtt_mtrr = -1;
> -	}
> +	arch_phys_wc_del(dev_priv->mm.gtt_mtrr);
> +	dev_priv->mm.gtt_mtrr = 0;

I think you can drop this gtt_mtrr = 0 asignment (and the one below) since
the driver will be unloaded anyway and no longer care. And with my
bikeshed on the first 1 patch it'd be wrong, too.
-Daniel

>  	io_mapping_free(dev_priv->gtt.mappable);
>  out_rmmap:
>  	pci_iounmap(dev->pdev, dev_priv->regs);
> @@ -1697,12 +1669,8 @@ int i915_driver_unload(struct drm_device *dev)
>  	cancel_delayed_work_sync(&dev_priv->mm.retire_work);
>  
>  	io_mapping_free(dev_priv->gtt.mappable);
> -	if (dev_priv->mm.gtt_mtrr >= 0) {
> -		mtrr_del(dev_priv->mm.gtt_mtrr,
> -			 dev_priv->gtt.mappable_base,
> -			 dev_priv->gtt.mappable_end);
> -		dev_priv->mm.gtt_mtrr = -1;
> -	}
> +	arch_phys_wc_del(dev_priv->mm.gtt_mtrr);
> +	dev_priv->mm.gtt_mtrr = 0;
>  
>  	acpi_video_unregister();
>  
> -- 
> 1.8.1.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC/PATCH v2 0/8] Clean up write-combining MTRR addition

[Daniel Vetter]

On Thu, May 09, 2013 at 12:46:19PM -0700, Andy Lutomirski wrote:
> A fair number of drivers (mostly graphics) add write-combining MTRRs.
> Most ignore errors and most add the MTRR even on PAT systems which don't
> need to use MTRRs.
> 
> This series adds new functions arch_phys_wc_{add,del} that, on PAT-less
> x86 systems with MTRRs, add MTRRs and report errors, and that do nothing
> otherwise.  (Other architectures, if any, with a similar mechanism could
> implement them.)
> 
> I've only tested the radeon driver, since I don't have test hardware
> easily available for the other drivers.
> 
> Benefits include:
>  - Simpler code
>  - No more complaints about MTRR conflict warnings on PAT systems
>  - Eventual unexporting of the MTRR API?
> 
> This series eliminates about half of the mtrr_add calls in drivers/.
> 
> Changes from v1:
>  - Helpers renamed
>  - Lots of bugs fixed
> 
> The series is also at:
> https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/log/?h=mtrr_cleanup/rfc_v2
> 
> Andy Lutomirski (8):
>   Add arch_phys_wc_{add,del} to manipulate WC MTRRs if needed
>   drm (ast,cirrus,mgag200,nouveau,savage,vmwgfx): Remove
>     drm_mtrr_{add,del}
>   drm: Update drm_addmap and drm_mmap to use PAT WC instead of MTRRs
>   drm,agpgart: Use pgprot_writecombine for AGP maps and make the MTRR
>     optional
>   i915: Use arch_phys_wc_{add,del}
>   radeon: Switch to arch_phys_wc_add and add a missing ..._del
>   uvesafb: Clean up MTRR code
>   drm: Remove mtrr_add and mtrr_del fallback hack for non-MTRR systems

With my two comments addressed, the entire series is

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

My knowledge for the userspace driver created drm maps in drm_vm.c is a
bit shoddy. Otoh most of the code I've seen using that is _horribly_
broken (as in userspace creates a register map that the kernel uses, with
no refcounting at all). Your changes look correct though, so I think this
is about as good as it gets.

Yours, Daniel
> 
>  Documentation/fb/uvesafb.txt           | 16 +++-----
>  arch/x86/include/asm/io.h              |  7 ++++
>  arch/x86/include/asm/mtrr.h            |  5 ++-
>  arch/x86/kernel/cpu/mtrr/main.c        | 48 +++++++++++++++++++++++
>  drivers/char/agp/frontend.c            |  8 ++--
>  drivers/gpu/drm/ast/ast_ttm.c          | 13 ++-----
>  drivers/gpu/drm/cirrus/cirrus_ttm.c    | 15 ++------
>  drivers/gpu/drm/drm_bufs.c             | 17 +++++----
>  drivers/gpu/drm/drm_pci.c              |  8 ++--
>  drivers/gpu/drm/drm_stub.c             | 10 +----
>  drivers/gpu/drm/drm_vm.c               | 22 +++++------
>  drivers/gpu/drm/i915/i915_dma.c        | 44 +++------------------
>  drivers/gpu/drm/mgag200/mgag200_ttm.c  | 14 ++-----
>  drivers/gpu/drm/nouveau/nouveau_ttm.c  | 13 ++-----
>  drivers/gpu/drm/radeon/radeon_object.c |  5 ++-
>  drivers/gpu/drm/savage/savage_bci.c    | 43 ++++++++-------------
>  drivers/gpu/drm/savage/savage_drv.h    |  5 +--
>  drivers/gpu/drm/vmwgfx/vmwgfx_drv.c    | 10 ++---
>  drivers/video/uvesafb.c                | 70 +++++++++-------------------------
>  include/drm/drmP.h                     | 34 +----------------
>  include/drm/drm_os_linux.h             | 16 --------
>  include/linux/io.h                     | 25 ++++++++++++
>  include/video/uvesafb.h                |  1 +
>  23 files changed, 181 insertions(+), 268 deletions(-)
> 
> -- 
> 1.8.1.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC/PATCH v2 1/8] Add arch_phys_wc_{add,del} to manipulate WC MTRRs if needed

[Andy Lutomirski]

On Fri, May 10, 2013 at 2:19 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Thu, May 09, 2013 at 12:46:20PM -0700, Andy Lutomirski wrote:
>> Several drivers currently use mtrr_add through various #ifdef guards
>> and/or drm wrappers.  The vast majority of them want to add WC MTRRs
>> on x86 systems and don't actually need the MTRR if PAT (i.e.
>> ioremap_wc, etc) are working.
>>
>> arch_phys_wc_add and arch_phys_wc_del are new functions, available
>> on all architectures and configurations, that add WC MTRRs on x86 if
>> needed (and handle errors) and do nothing at all otherwise.  They're
>> also easier to use than mtrr_add and mtrr_del, so the call sites can
>> be simplified.
>>
>> As an added benefit, this will avoid wasting MTRRs and possibly
>> warning pointlessly on PAT-supporting systems.
>>
>> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
>> ---
>>  arch/x86/include/asm/io.h       |  7 ++++++
>>  arch/x86/include/asm/mtrr.h     |  5 ++++-
>>  arch/x86/kernel/cpu/mtrr/main.c | 48 +++++++++++++++++++++++++++++++++++++++++
>>  include/linux/io.h              | 25 +++++++++++++++++++++
>>  4 files changed, 84 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
>> index d8e8eef..34f69cb 100644
>> --- a/arch/x86/include/asm/io.h
>> +++ b/arch/x86/include/asm/io.h
>> @@ -345,4 +345,11 @@ extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
>>
>>  #define IO_SPACE_LIMIT 0xffff
>>
>> +#ifdef CONFIG_MTRR
>> +extern int __must_check arch_phys_wc_add(unsigned long base,
>> +                                      unsigned long size);
>> +extern void arch_phys_wc_del(int handle);
>> +#define arch_phys_wc_add arch_phys_wc_add
>> +#endif
>> +
>>  #endif /* _ASM_X86_IO_H */
>> diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
>> index e235582..10d0fba 100644
>> --- a/arch/x86/include/asm/mtrr.h
>> +++ b/arch/x86/include/asm/mtrr.h
>> @@ -26,7 +26,10 @@
>>  #include <uapi/asm/mtrr.h>
>>
>>
>> -/*  The following functions are for use by other drivers  */
>> +/*
>> + * The following functions are for use by other drivers that cannot use
>> + * arch_phys_wc_add and arch_phys_wc_del.
>> + */
>>  # ifdef CONFIG_MTRR
>>  extern u8 mtrr_type_lookup(u64 addr, u64 end);
>>  extern void mtrr_save_fixed_ranges(void *);
>> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
>> index 726bf96..23bd49a 100644
>> --- a/arch/x86/kernel/cpu/mtrr/main.c
>> +++ b/arch/x86/kernel/cpu/mtrr/main.c
>> @@ -51,6 +51,7 @@
>>  #include <asm/e820.h>
>>  #include <asm/mtrr.h>
>>  #include <asm/msr.h>
>> +#include <asm/pat.h>
>>
>>  #include "mtrr.h"
>>
>> @@ -524,6 +525,53 @@ int mtrr_del(int reg, unsigned long base, unsigned long size)
>>  }
>>  EXPORT_SYMBOL(mtrr_del);
>>
>> +/**
>> + * arch_phys_wc_add - add a WC MTRR and handle errors if PAT is unavailable
>> + * @base: Physical base address
>> + * @size: Size of region
>> + *
>> + * If PAT is available, this does nothing.  If PAT is unavailable, it
>> + * attempts to add a WC MTRR covering size bytes starting at base and
>> + * logs an error if this fails.
>> + *
>> + * Drivers must store the return value to pass to mtrr_del_wc_if_needed,
>> + * but drivers should not try to interpret that return value.
>> + */
>> +int arch_phys_wc_add(unsigned long base, unsigned long size)
>> +{
>> +     int ret;
>> +
>> +     if (pat_enabled)
>> +             return 0;  /* Success!  (We don't need to do anything.) */
>
> Shouldn't we #define a big number for this case since mtrr_add returns
> 0-based mtrr indices? Rather unlikely that the very first mtrr is unused I
> know, but still feels like a cleaner interface. And we don't need to leak
> that #define out at all to users of this interface.

I did something more like that in v1, but I like having the property
that arch_phys_wc_del(0) does nothing as opposed to possibly breaking
the system.  Given that almost all of these things are stored in
kzalloced space, this seems safer to me.  The return value here could
just as easily be -ENOSYS, but nothing should care.

There is an issue, though: the drm maps interface is leaking the
return values to userspace via a couple of ioctls, so I should fix it
to at least return the correct value.  (Why that interface includes an
mtrr number is a mystery to me.)

Have I convinced you that my bike shed color is okay?  I'll send out a
v3 later today with a fix for the leaking-to-userspace issue and I'll
fix the i915 thing.

--Andy

Re: [RFC/PATCH v2 1/8] Add arch_phys_wc_{add,del} to manipulate WC MTRRs if needed

[Daniel Vetter]

On Fri, May 10, 2013 at 11:00:56AM -0700, Andy Lutomirski wrote:
> On Fri, May 10, 2013 at 2:19 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
> > On Thu, May 09, 2013 at 12:46:20PM -0700, Andy Lutomirski wrote:
> >> Several drivers currently use mtrr_add through various #ifdef guards
> >> and/or drm wrappers.  The vast majority of them want to add WC MTRRs
> >> on x86 systems and don't actually need the MTRR if PAT (i.e.
> >> ioremap_wc, etc) are working.
> >>
> >> arch_phys_wc_add and arch_phys_wc_del are new functions, available
> >> on all architectures and configurations, that add WC MTRRs on x86 if
> >> needed (and handle errors) and do nothing at all otherwise.  They're
> >> also easier to use than mtrr_add and mtrr_del, so the call sites can
> >> be simplified.
> >>
> >> As an added benefit, this will avoid wasting MTRRs and possibly
> >> warning pointlessly on PAT-supporting systems.
> >>
> >> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
> >> ---
> >>  arch/x86/include/asm/io.h       |  7 ++++++
> >>  arch/x86/include/asm/mtrr.h     |  5 ++++-
> >>  arch/x86/kernel/cpu/mtrr/main.c | 48 +++++++++++++++++++++++++++++++++++++++++
> >>  include/linux/io.h              | 25 +++++++++++++++++++++
> >>  4 files changed, 84 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
> >> index d8e8eef..34f69cb 100644
> >> --- a/arch/x86/include/asm/io.h
> >> +++ b/arch/x86/include/asm/io.h
> >> @@ -345,4 +345,11 @@ extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
> >>
> >>  #define IO_SPACE_LIMIT 0xffff
> >>
> >> +#ifdef CONFIG_MTRR
> >> +extern int __must_check arch_phys_wc_add(unsigned long base,
> >> +                                      unsigned long size);
> >> +extern void arch_phys_wc_del(int handle);
> >> +#define arch_phys_wc_add arch_phys_wc_add
> >> +#endif
> >> +
> >>  #endif /* _ASM_X86_IO_H */
> >> diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
> >> index e235582..10d0fba 100644
> >> --- a/arch/x86/include/asm/mtrr.h
> >> +++ b/arch/x86/include/asm/mtrr.h
> >> @@ -26,7 +26,10 @@
> >>  #include <uapi/asm/mtrr.h>
> >>
> >>
> >> -/*  The following functions are for use by other drivers  */
> >> +/*
> >> + * The following functions are for use by other drivers that cannot use
> >> + * arch_phys_wc_add and arch_phys_wc_del.
> >> + */
> >>  # ifdef CONFIG_MTRR
> >>  extern u8 mtrr_type_lookup(u64 addr, u64 end);
> >>  extern void mtrr_save_fixed_ranges(void *);
> >> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> >> index 726bf96..23bd49a 100644
> >> --- a/arch/x86/kernel/cpu/mtrr/main.c
> >> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> >> @@ -51,6 +51,7 @@
> >>  #include <asm/e820.h>
> >>  #include <asm/mtrr.h>
> >>  #include <asm/msr.h>
> >> +#include <asm/pat.h>
> >>
> >>  #include "mtrr.h"
> >>
> >> @@ -524,6 +525,53 @@ int mtrr_del(int reg, unsigned long base, unsigned long size)
> >>  }
> >>  EXPORT_SYMBOL(mtrr_del);
> >>
> >> +/**
> >> + * arch_phys_wc_add - add a WC MTRR and handle errors if PAT is unavailable
> >> + * @base: Physical base address
> >> + * @size: Size of region
> >> + *
> >> + * If PAT is available, this does nothing.  If PAT is unavailable, it
> >> + * attempts to add a WC MTRR covering size bytes starting at base and
> >> + * logs an error if this fails.
> >> + *
> >> + * Drivers must store the return value to pass to mtrr_del_wc_if_needed,
> >> + * but drivers should not try to interpret that return value.
> >> + */
> >> +int arch_phys_wc_add(unsigned long base, unsigned long size)
> >> +{
> >> +     int ret;
> >> +
> >> +     if (pat_enabled)
> >> +             return 0;  /* Success!  (We don't need to do anything.) */
> >
> > Shouldn't we #define a big number for this case since mtrr_add returns
> > 0-based mtrr indices? Rather unlikely that the very first mtrr is unused I
> > know, but still feels like a cleaner interface. And we don't need to leak
> > that #define out at all to users of this interface.
> 
> I did something more like that in v1, but I like having the property
> that arch_phys_wc_del(0) does nothing as opposed to possibly breaking
> the system.  Given that almost all of these things are stored in
> kzalloced space, this seems safer to me.  The return value here could
> just as easily be -ENOSYS, but nothing should care.
> 
> There is an issue, though: the drm maps interface is leaking the
> return values to userspace via a couple of ioctls, so I should fix it
> to at least return the correct value.  (Why that interface includes an
> mtrr number is a mystery to me.)

Old drm interfaces are horrible. Best approach is to simply stay far away
from them ...

> Have I convinced you that my bike shed color is okay?  I'll send out a
> v3 later today with a fix for the leaking-to-userspace issue and I'll
> fix the i915 thing.

A comment in your arch_phys_wc_add/del functions that we do have an mtrr
with index 0, but won't ever get that would be fine with me. Still feels a
bit irky though ;-)

Cheers, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC/PATCH v2 1/8] Add arch_phys_wc_{add,del} to manipulate WC MTRRs if needed

[Andy Lutomirski]

On Fri, May 10, 2013 at 12:09 PM, Daniel Vetter <daniel@ffwll.ch> wrote:
> On Fri, May 10, 2013 at 11:00:56AM -0700, Andy Lutomirski wrote:
>> On Fri, May 10, 2013 at 2:19 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
>> > On Thu, May 09, 2013 at 12:46:20PM -0700, Andy Lutomirski wrote:
>> >> Several drivers currently use mtrr_add through various #ifdef guards
>> >> and/or drm wrappers.  The vast majority of them want to add WC MTRRs
>> >> on x86 systems and don't actually need the MTRR if PAT (i.e.
>> >> ioremap_wc, etc) are working.
>> >>
>> >> arch_phys_wc_add and arch_phys_wc_del are new functions, available
>> >> on all architectures and configurations, that add WC MTRRs on x86 if
>> >> needed (and handle errors) and do nothing at all otherwise.  They're
>> >> also easier to use than mtrr_add and mtrr_del, so the call sites can
>> >> be simplified.
>> >>
>> >> As an added benefit, this will avoid wasting MTRRs and possibly
>> >> warning pointlessly on PAT-supporting systems.
>> >>
>> >> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
>> >> ---
>> >>  arch/x86/include/asm/io.h       |  7 ++++++
>> >>  arch/x86/include/asm/mtrr.h     |  5 ++++-
>> >>  arch/x86/kernel/cpu/mtrr/main.c | 48 +++++++++++++++++++++++++++++++++++++++++
>> >>  include/linux/io.h              | 25 +++++++++++++++++++++
>> >>  4 files changed, 84 insertions(+), 1 deletion(-)
>> >>
>> >> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
>> >> index d8e8eef..34f69cb 100644
>> >> --- a/arch/x86/include/asm/io.h
>> >> +++ b/arch/x86/include/asm/io.h
>> >> @@ -345,4 +345,11 @@ extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
>> >>
>> >>  #define IO_SPACE_LIMIT 0xffff
>> >>
>> >> +#ifdef CONFIG_MTRR
>> >> +extern int __must_check arch_phys_wc_add(unsigned long base,
>> >> +                                      unsigned long size);
>> >> +extern void arch_phys_wc_del(int handle);
>> >> +#define arch_phys_wc_add arch_phys_wc_add
>> >> +#endif
>> >> +
>> >>  #endif /* _ASM_X86_IO_H */
>> >> diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
>> >> index e235582..10d0fba 100644
>> >> --- a/arch/x86/include/asm/mtrr.h
>> >> +++ b/arch/x86/include/asm/mtrr.h
>> >> @@ -26,7 +26,10 @@
>> >>  #include <uapi/asm/mtrr.h>
>> >>
>> >>
>> >> -/*  The following functions are for use by other drivers  */
>> >> +/*
>> >> + * The following functions are for use by other drivers that cannot use
>> >> + * arch_phys_wc_add and arch_phys_wc_del.
>> >> + */
>> >>  # ifdef CONFIG_MTRR
>> >>  extern u8 mtrr_type_lookup(u64 addr, u64 end);
>> >>  extern void mtrr_save_fixed_ranges(void *);
>> >> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
>> >> index 726bf96..23bd49a 100644
>> >> --- a/arch/x86/kernel/cpu/mtrr/main.c
>> >> +++ b/arch/x86/kernel/cpu/mtrr/main.c
>> >> @@ -51,6 +51,7 @@
>> >>  #include <asm/e820.h>
>> >>  #include <asm/mtrr.h>
>> >>  #include <asm/msr.h>
>> >> +#include <asm/pat.h>
>> >>
>> >>  #include "mtrr.h"
>> >>
>> >> @@ -524,6 +525,53 @@ int mtrr_del(int reg, unsigned long base, unsigned long size)
>> >>  }
>> >>  EXPORT_SYMBOL(mtrr_del);
>> >>
>> >> +/**
>> >> + * arch_phys_wc_add - add a WC MTRR and handle errors if PAT is unavailable
>> >> + * @base: Physical base address
>> >> + * @size: Size of region
>> >> + *
>> >> + * If PAT is available, this does nothing.  If PAT is unavailable, it
>> >> + * attempts to add a WC MTRR covering size bytes starting at base and
>> >> + * logs an error if this fails.
>> >> + *
>> >> + * Drivers must store the return value to pass to mtrr_del_wc_if_needed,
>> >> + * but drivers should not try to interpret that return value.
>> >> + */
>> >> +int arch_phys_wc_add(unsigned long base, unsigned long size)
>> >> +{
>> >> +     int ret;
>> >> +
>> >> +     if (pat_enabled)
>> >> +             return 0;  /* Success!  (We don't need to do anything.) */
>> >
>> > Shouldn't we #define a big number for this case since mtrr_add returns
>> > 0-based mtrr indices? Rather unlikely that the very first mtrr is unused I
>> > know, but still feels like a cleaner interface. And we don't need to leak
>> > that #define out at all to users of this interface.
>>
>> I did something more like that in v1, but I like having the property
>> that arch_phys_wc_del(0) does nothing as opposed to possibly breaking
>> the system.  Given that almost all of these things are stored in
>> kzalloced space, this seems safer to me.  The return value here could
>> just as easily be -ENOSYS, but nothing should care.
>>
>> There is an issue, though: the drm maps interface is leaking the
>> return values to userspace via a couple of ioctls, so I should fix it
>> to at least return the correct value.  (Why that interface includes an
>> mtrr number is a mystery to me.)
>
> Old drm interfaces are horrible. Best approach is to simply stay far away
> from them ...
>
>> Have I convinced you that my bike shed color is okay?  I'll send out a
>> v3 later today with a fix for the leaking-to-userspace issue and I'll
>> fix the i915 thing.
>
> A comment in your arch_phys_wc_add/del functions that we do have an mtrr
> with index 0, but won't ever get that would be fine with me. Still feels a
> bit irky though ;-)

Hmm.  Maybe you missed the hack I ended up using a couple of lines
below.  I'm always using strictly positive values to indicate a real
MTRR -- I'm adding 1000 to the result if we actually do anything.  So
a return value of 0 is genuinely safe.  (I still have to fix up the
two places in the drm code that pass that hacked-up value back to
userspace.)

--Andy

Re: [RFC/PATCH v2 1/8] Add arch_phys_wc_{add,del} to manipulate WC MTRRs if needed

[Daniel Vetter]

On Fri, May 10, 2013 at 12:27:54PM -0700, Andy Lutomirski wrote:
> On Fri, May 10, 2013 at 12:09 PM, Daniel Vetter <daniel@ffwll.ch> wrote:
> > On Fri, May 10, 2013 at 11:00:56AM -0700, Andy Lutomirski wrote:
> >> On Fri, May 10, 2013 at 2:19 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
> >> > On Thu, May 09, 2013 at 12:46:20PM -0700, Andy Lutomirski wrote:
> >> >> Several drivers currently use mtrr_add through various #ifdef guards
> >> >> and/or drm wrappers.  The vast majority of them want to add WC MTRRs
> >> >> on x86 systems and don't actually need the MTRR if PAT (i.e.
> >> >> ioremap_wc, etc) are working.
> >> >>
> >> >> arch_phys_wc_add and arch_phys_wc_del are new functions, available
> >> >> on all architectures and configurations, that add WC MTRRs on x86 if
> >> >> needed (and handle errors) and do nothing at all otherwise.  They're
> >> >> also easier to use than mtrr_add and mtrr_del, so the call sites can
> >> >> be simplified.
> >> >>
> >> >> As an added benefit, this will avoid wasting MTRRs and possibly
> >> >> warning pointlessly on PAT-supporting systems.
> >> >>
> >> >> Signed-off-by: Andy Lutomirski <luto@amacapital.net>
> >> >> ---
> >> >>  arch/x86/include/asm/io.h       |  7 ++++++
> >> >>  arch/x86/include/asm/mtrr.h     |  5 ++++-
> >> >>  arch/x86/kernel/cpu/mtrr/main.c | 48 +++++++++++++++++++++++++++++++++++++++++
> >> >>  include/linux/io.h              | 25 +++++++++++++++++++++
> >> >>  4 files changed, 84 insertions(+), 1 deletion(-)
> >> >>
> >> >> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
> >> >> index d8e8eef..34f69cb 100644
> >> >> --- a/arch/x86/include/asm/io.h
> >> >> +++ b/arch/x86/include/asm/io.h
> >> >> @@ -345,4 +345,11 @@ extern bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
> >> >>
> >> >>  #define IO_SPACE_LIMIT 0xffff
> >> >>
> >> >> +#ifdef CONFIG_MTRR
> >> >> +extern int __must_check arch_phys_wc_add(unsigned long base,
> >> >> +                                      unsigned long size);
> >> >> +extern void arch_phys_wc_del(int handle);
> >> >> +#define arch_phys_wc_add arch_phys_wc_add
> >> >> +#endif
> >> >> +
> >> >>  #endif /* _ASM_X86_IO_H */
> >> >> diff --git a/arch/x86/include/asm/mtrr.h b/arch/x86/include/asm/mtrr.h
> >> >> index e235582..10d0fba 100644
> >> >> --- a/arch/x86/include/asm/mtrr.h
> >> >> +++ b/arch/x86/include/asm/mtrr.h
> >> >> @@ -26,7 +26,10 @@
> >> >>  #include <uapi/asm/mtrr.h>
> >> >>
> >> >>
> >> >> -/*  The following functions are for use by other drivers  */
> >> >> +/*
> >> >> + * The following functions are for use by other drivers that cannot use
> >> >> + * arch_phys_wc_add and arch_phys_wc_del.
> >> >> + */
> >> >>  # ifdef CONFIG_MTRR
> >> >>  extern u8 mtrr_type_lookup(u64 addr, u64 end);
> >> >>  extern void mtrr_save_fixed_ranges(void *);
> >> >> diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
> >> >> index 726bf96..23bd49a 100644
> >> >> --- a/arch/x86/kernel/cpu/mtrr/main.c
> >> >> +++ b/arch/x86/kernel/cpu/mtrr/main.c
> >> >> @@ -51,6 +51,7 @@
> >> >>  #include <asm/e820.h>
> >> >>  #include <asm/mtrr.h>
> >> >>  #include <asm/msr.h>
> >> >> +#include <asm/pat.h>
> >> >>
> >> >>  #include "mtrr.h"
> >> >>
> >> >> @@ -524,6 +525,53 @@ int mtrr_del(int reg, unsigned long base, unsigned long size)
> >> >>  }
> >> >>  EXPORT_SYMBOL(mtrr_del);
> >> >>
> >> >> +/**
> >> >> + * arch_phys_wc_add - add a WC MTRR and handle errors if PAT is unavailable
> >> >> + * @base: Physical base address
> >> >> + * @size: Size of region
> >> >> + *
> >> >> + * If PAT is available, this does nothing.  If PAT is unavailable, it
> >> >> + * attempts to add a WC MTRR covering size bytes starting at base and
> >> >> + * logs an error if this fails.
> >> >> + *
> >> >> + * Drivers must store the return value to pass to mtrr_del_wc_if_needed,
> >> >> + * but drivers should not try to interpret that return value.
> >> >> + */
> >> >> +int arch_phys_wc_add(unsigned long base, unsigned long size)
> >> >> +{
> >> >> +     int ret;
> >> >> +
> >> >> +     if (pat_enabled)
> >> >> +             return 0;  /* Success!  (We don't need to do anything.) */
> >> >
> >> > Shouldn't we #define a big number for this case since mtrr_add returns
> >> > 0-based mtrr indices? Rather unlikely that the very first mtrr is unused I
> >> > know, but still feels like a cleaner interface. And we don't need to leak
> >> > that #define out at all to users of this interface.
> >>
> >> I did something more like that in v1, but I like having the property
> >> that arch_phys_wc_del(0) does nothing as opposed to possibly breaking
> >> the system.  Given that almost all of these things are stored in
> >> kzalloced space, this seems safer to me.  The return value here could
> >> just as easily be -ENOSYS, but nothing should care.
> >>
> >> There is an issue, though: the drm maps interface is leaking the
> >> return values to userspace via a couple of ioctls, so I should fix it
> >> to at least return the correct value.  (Why that interface includes an
> >> mtrr number is a mystery to me.)
> >
> > Old drm interfaces are horrible. Best approach is to simply stay far away
> > from them ...
> >
> >> Have I convinced you that my bike shed color is okay?  I'll send out a
> >> v3 later today with a fix for the leaking-to-userspace issue and I'll
> >> fix the i915 thing.
> >
> > A comment in your arch_phys_wc_add/del functions that we do have an mtrr
> > with index 0, but won't ever get that would be fine with me. Still feels a
> > bit irky though ;-)
> 
> Hmm.  Maybe you missed the hack I ended up using a couple of lines
> below.  I'm always using strictly positive values to indicate a real
> MTRR -- I'm adding 1000 to the result if we actually do anything.  So
> a return value of 0 is genuinely safe.  (I still have to fix up the
> two places in the drm code that pass that hacked-up value back to
> userspace.)

Oops, I've indeed missed that one. Only noticed the special 0 and started
hunting down the semantics of mtrr_add. With that cleared up this is

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch