On Tue 20 Jun 13:16 PDT 2017, Arnd Bergmann wrote:
> 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
> purposes:
>
> 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 <a...@arndb.de>
Acked-by: Bjorn Andersson <bjorn.anders...@linaro.org>
Regards,
Bjorn
> ---
> 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,
> --
> 2.9.0
>
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