diff mbox series

[v1,3/4] iommu/tegra: gart: Constify number of GART pages

Message ID 954659be6760130f6ffd5e733db2ad58cbb8e6e4.1523304324.git.digetx@gmail.com
State Deferred
Headers show
Series Tegra GART fixes and improvements | expand

Commit Message

Dmitry Osipenko April 9, 2018, 8:07 p.m. UTC 
GART has a fixed aperture size, hence the number of pages is constant.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/iommu/tegra-gart.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

Comments

Thierry Reding April 27, 2018, 9:49 a.m. UTC | #1 
On Mon, Apr 09, 2018 at 11:07:21PM +0300, Dmitry Osipenko wrote:
> GART has a fixed aperture size, hence the number of pages is constant.
> 
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  drivers/iommu/tegra-gart.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)

This doesn't really give a good explanation of why you want to do this.
While it is certainly true that the aperture is fixed in size, I can
imagine cases where somebody would want to restrict the aperture size
(perhaps there's a fixed mapping somewhere near the end of the mapping
that Linux shouldn't touch, or the GART aperture could be reduced to
simulate out of IOVA memory situations).

Without a good explanation why this is necessary I don't see why the
current code should be changed.

Thierry
diff mbox series

Patch

diff --git a/drivers/iommu/tegra-gart.c b/drivers/iommu/tegra-gart.c
index 89ec24c6952c..4a0607669d34 100644
--- a/drivers/iommu/tegra-gart.c
+++ b/drivers/iommu/tegra-gart.c
@@ -33,6 +33,8 @@ 
 
 #include <asm/cacheflush.h>
 
+#define GART_APERTURE_SIZE	SZ_32M
+
 /* bitmap of the page sizes currently supported */
 #define GART_IOMMU_PGSIZES	(SZ_4K)
 
@@ -47,6 +49,8 @@ 
 #define GART_PAGE_MASK						\
 	(~(GART_PAGE_SIZE - 1) & ~GART_ENTRY_PHYS_ADDR_VALID)
 
+#define GART_PAGECOUNT		(GART_APERTURE_SIZE >> GART_PAGE_SHIFT)
+
 struct gart_client {
 	struct device		*dev;
 	struct list_head	list;
@@ -55,7 +59,6 @@  struct gart_client {
 struct gart_device {
 	void __iomem		*regs;
 	u32			*savedata;
-	u32			page_count;	/* total remappable size */
 	dma_addr_t		iovmm_base;	/* offset to vmm_area */
 	spinlock_t		pte_lock;	/* for pagetable */
 	struct list_head	client;
@@ -91,7 +94,7 @@  static struct gart_domain *to_gart_domain(struct iommu_domain *dom)
 
 #define for_each_gart_pte(gart, iova)					\
 	for (iova = gart->iovmm_base;					\
-	     iova < gart->iovmm_base + GART_PAGE_SIZE * gart->page_count; \
+	     iova < gart->iovmm_base + GART_APERTURE_SIZE; 		\
 	     iova += GART_PAGE_SIZE)
 
 static inline void gart_set_pte(struct gart_device *gart,
@@ -158,7 +161,7 @@  static inline bool gart_iova_range_valid(struct gart_device *gart,
 	iova_start = iova;
 	iova_end = iova_start + bytes - 1;
 	gart_start = gart->iovmm_base;
-	gart_end = gart_start + gart->page_count * GART_PAGE_SIZE - 1;
+	gart_end = gart_start + GART_APERTURE_SIZE - 1;
 
 	if (iova_start < gart_start)
 		return false;
@@ -241,7 +244,7 @@  static struct iommu_domain *gart_iommu_domain_alloc(unsigned type)
 	gart_domain->gart = gart;
 	gart_domain->domain.geometry.aperture_start = gart->iovmm_base;
 	gart_domain->domain.geometry.aperture_end = gart->iovmm_base +
-					gart->page_count * GART_PAGE_SIZE - 1;
+							GART_APERTURE_SIZE - 1;
 	gart_domain->domain.geometry.force_aperture = true;
 
 	return &gart_domain->domain;
@@ -463,9 +466,8 @@  static int tegra_gart_probe(struct platform_device *pdev)
 	INIT_LIST_HEAD(&gart->client);
 	gart->regs = gart_regs;
 	gart->iovmm_base = (dma_addr_t)res_remap->start;
-	gart->page_count = (resource_size(res_remap) >> GART_PAGE_SHIFT);
 
-	gart->savedata = vmalloc(sizeof(u32) * gart->page_count);
+	gart->savedata = vmalloc(sizeof(u32) * GART_PAGECOUNT);
 	if (!gart->savedata) {
 		dev_err(dev, "failed to allocate context save area\n");
 		return -ENOMEM;