[PATCH 1/2] drm/msm: gpu: don't abuse dma_alloc for non-DMA allocations

From: Arnd Bergmann
Date: Tue Jun 20 2017 - 16:17:45 EST

In zap_shader_load_mdt(), we pass a pointer to a phys_addr_t
into dmam_alloc_coherent, which the compiler warns about:

drivers/gpu/drm/msm/adreno/a5xx_gpu.c: In function 'zap_shader_load_mdt':
drivers/gpu/drm/msm/adreno/a5xx_gpu.c:54:50: error: passing argument 3 of 'dmam_alloc_coherent' from incompatible pointer type [-Werror=incompatible-pointer-types]

The returned DMA address is later passed on to a function that
takes a phys_addr_t, so it's clearly wrong to use the DMA
mapping interface here: the memory may be uncached, or the
address may be completely wrong if there is an IOMMU connected
to the device.

My interpretation is that using dmam_alloc_coherent() had two

a) get a chunk of consecutive memory that may be larger than
the limit for kmalloc()

b) use the devres infrastructure to simplify the unwinding
in the error case.

I think ideally we'd use a devres-based version of
alloc_pages_exact() here, but since that doesn't exist,
let's use devm_get_free_pages() instead. This wastes a little
memory as the size gets rounded up to a power of two, but
is otherwise harmless. If we want to save memory here, calling
devm_free_pages() to release the memory once it is no longer
needed is probably better anyway.

Fixes: 7c65817e6d38 ("drm/msm: gpu: Enable zap shader for A5XX")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
drivers/gpu/drm/msm/adreno/a5xx_gpu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
index b4b54f1c24bc..eee9ac81aaa1 100644
--- a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
@@ -51,11 +51,13 @@ static int zap_shader_load_mdt(struct device *dev, const char *fwname)

/* Allocate memory for the firmware image */
- mem_region = dmam_alloc_coherent(dev, mem_size, &mem_phys, GFP_KERNEL);
+ mem_region = (void *)devm_get_free_pages(dev, GFP_KERNEL,
+ get_order(mem_size));
if (!mem_region) {
ret = -ENOMEM;
goto out;
+ mem_phys = virt_to_phys(mem_region);

/* Load the rest of the MDT */
ret = qcom_mdt_load(dev, fw, fwname, GPU_PAS_ID, mem_region, mem_phys,