Unverified Commit f0a1ab65 authored by Matt Coster's avatar Matt Coster
Browse files

drm/imagination: Use cached memory with dma_coherent 



The TI k3-j721s2 platform does not allow us to use uncached memory
(which is what the driver currently does) without disabling cache snooping
on the AXI ACE-Lite interface, which would be too much of a performance
hit.

Given the platform is dma-coherent, we can simply force all
device-accessible memory allocations through the CPU cache. In fact, this
can be done whenever the dma_coherent attribute is present.

Reviewed-by: default avatarFrank Binns <frank.binns@imgtec.com>
Link: https://lore.kernel.org/r/20250410-sets-bxs-4-64-patch-v1-v6-15-eda620c5865f@imgtec.com


Signed-off-by: default avatarMatt Coster <matt.coster@imgtec.com>
parent 171f378d

drivers/gpu/drm/imagination/pvr_gem.c

+7 −3
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <linux/log2.h>

#include <linux/mutex.h>

#include <linux/pagemap.h>

#include <linux/property.h>

#include <linux/refcount.h>

#include <linux/scatterlist.h>
@@ -334,6 +335,7 @@ struct drm_gem_object *pvr_gem_create_object(struct drm_device *drm_dev, size_t 
struct pvr_gem_object *

pvr_gem_object_create(struct pvr_device *pvr_dev, size_t size, u64 flags)

{

	struct drm_device *drm_dev = from_pvr_device(pvr_dev);

	struct drm_gem_shmem_object *shmem_obj;

	struct pvr_gem_object *pvr_obj;

	struct sg_table *sgt;
@@ -343,7 +345,10 @@ pvr_gem_object_create(struct pvr_device *pvr_dev, size_t size, u64 flags) 
	if (size == 0 || !pvr_gem_object_flags_validate(flags))

		return ERR_PTR(-EINVAL);



	shmem_obj = drm_gem_shmem_create(from_pvr_device(pvr_dev), size);

	if (device_get_dma_attr(drm_dev->dev) == DEV_DMA_COHERENT)

		flags |= PVR_BO_CPU_CACHED;



	shmem_obj = drm_gem_shmem_create(drm_dev, size);

	if (IS_ERR(shmem_obj))

		return ERR_CAST(shmem_obj);
@@ -358,8 +363,7 @@ pvr_gem_object_create(struct pvr_device *pvr_dev, size_t size, u64 flags) 
		goto err_shmem_object_free;

	}



	dma_sync_sgtable_for_device(shmem_obj->base.dev->dev, sgt,

				    DMA_BIDIRECTIONAL);

	dma_sync_sgtable_for_device(drm_dev->dev, sgt, DMA_BIDIRECTIONAL);



	/*

	 * Do this last because pvr_gem_object_zero() requires a fully

drivers/gpu/drm/imagination/pvr_gem.h

+4 −2
Original line number Diff line number Diff line
@@ -44,8 +44,10 @@ struct pvr_file; 
 * Bits not defined anywhere are "undefined".

 *

 * CPU mapping options

 *    :PVR_BO_CPU_CACHED: By default, all GEM objects are mapped write-combined on the CPU. Set this

 *       flag to override this behaviour and map the object cached.

 *    :PVR_BO_CPU_CACHED: By default, all GEM objects are mapped write-combined on the CPU. Set

 *       this flag to override this behaviour and map the object cached. If the dma_coherent

 *       property is present in devicetree, all allocations will be mapped as if this flag was set.

 *       This does not require any additional consideration at allocation time.

 *

 * Firmware options

 *    :PVR_BO_FW_NO_CLEAR_ON_RESET: By default, all FW objects are cleared and reinitialised on hard

drivers/gpu/drm/imagination/pvr_mmu.c

+7 −1
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/dma-mapping.h>

#include <linux/kmemleak.h>

#include <linux/minmax.h>

#include <linux/property.h>

#include <linux/sizes.h>



#define PVR_SHIFT_FROM_SIZE(size_) (__builtin_ctzll(size_))
@@ -259,6 +260,7 @@ pvr_mmu_backing_page_init(struct pvr_mmu_backing_page *page, 
	struct device *dev = from_pvr_device(pvr_dev)->dev;



	struct page *raw_page;

	pgprot_t prot;

	int err;



	dma_addr_t dma_addr;
@@ -268,7 +270,11 @@ pvr_mmu_backing_page_init(struct pvr_mmu_backing_page *page, 
	if (!raw_page)

		return -ENOMEM;



	host_ptr = vmap(&raw_page, 1, VM_MAP, pgprot_writecombine(PAGE_KERNEL));

	prot = PAGE_KERNEL;

	if (device_get_dma_attr(dev) != DEV_DMA_COHERENT)

		prot = pgprot_writecombine(prot);



	host_ptr = vmap(&raw_page, 1, VM_MAP, prot);

	if (!host_ptr) {

		err = -ENOMEM;

		goto err_free_page;