On 03/06/2021 22:21, Alyssa Rosenzweig wrote:
> The value of the AFBC_FEATURES register is required by userspace to
> determine AFBC support on Bifrost. A user on our IRC channel (#panfrost)
> reported a workload that raised a fault on one system's Mali G31 but
> worked flawlessly with another system's Mali G31. We determined the
> cause to be missing AFBC support on one vendor's Mali implementation --
> it turns out AFBC is optional on Bifrost!
I was surprised this had been missed, but it turns out the DDK doesn't
care so kbase doesn't expose it either! I guess this is one of those
"recompile the driver to support your hardware" cases with the blob.
> Whether AFBC is supported or not is exposed in the AFBC_FEATURES
> register on Bifrost, which reads back as 0 on Midgard. A zero value
> indicates AFBC is fully supported, provided the architecture itself
> supports AFBC, allowing backwards-compatibility with Midgard. Bits 0 and
> 15 indicate that AFBC support is absent for texturing and rendering
> respectively.
>
> The user experiencing the fault reports that AFBC_FEATURES reads back
> 0x10001 on their system, confirming the architectural lack of AFBC.
> Userspace needs this this parameter to know to disable AFBC on that
> chip, and perhaps others.
>
> v2: Fix typo from copy-paste fail.
>
> v3: Bump the UABI version. This commit was cherry-picked from another
> series so chalking this up to a rebase fail.
I'd like to say third time's the charm, but...
>
> Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@xxxxxxxxxxxxx>
> Cc: Rob Herring <robh@xxxxxxxxxx>
> Cc: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
> Cc: Steven Price <steven.price@xxxxxxx>
> ---
> drivers/gpu/drm/panfrost/panfrost_device.h | 1 +
> drivers/gpu/drm/panfrost/panfrost_drv.c | 3 ++-
> drivers/gpu/drm/panfrost/panfrost_gpu.c | 1 +
> drivers/gpu/drm/panfrost/panfrost_regs.h | 1 +
> include/uapi/drm/panfrost_drm.h | 1 +
> 5 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_device.h b/drivers/gpu/drm/panfrost/panfrost_device.h
> index 597cf1459..f614e9877 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_device.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_device.h
> @@ -45,6 +45,7 @@ struct panfrost_features {
> u32 thread_max_workgroup_sz;
> u32 thread_max_barrier_sz;
> u32 coherency_features;
> + u32 afbc_features;
> u32 texture_features[4];
> u32 js_features[16];
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index ca07098a6..365ee53f0 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -63,6 +63,7 @@ static int panfrost_ioctl_get_param(struct drm_device *ddev, void *data, struct
> PANFROST_FEATURE(THREAD_MAX_BARRIER_SZ,
> thread_max_barrier_sz);
> PANFROST_FEATURE(COHERENCY_FEATURES, coherency_features);
> + PANFROST_FEATURE(AFBC_FEATURES, afbc_features);
> PANFROST_FEATURE_ARRAY(TEXTURE_FEATURES, texture_features, 3);
> PANFROST_FEATURE_ARRAY(JS_FEATURES, js_features, 15);
> PANFROST_FEATURE(NR_CORE_GROUPS, nr_core_groups);
> @@ -559,7 +560,7 @@ static const struct drm_driver panfrost_drm_driver = {
Missing context:
> /*
> * Panfrost driver version:
> * - 1.0 - initial interface
> * - 1.1 - adds HEAP and NOEXEC flags for CREATE_BO
> */
It would be good to add the new version in this comment to document what
it adds. With that added:
Reviewed-by: Steven Price <steven.price@xxxxxxx>
Steve
> .desc = "panfrost DRM",
> .date = "20180908",
> .major = 1,
> - .minor = 1,
> + .minor = 2,
>
> .gem_create_object = panfrost_gem_create_object,
> .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gpu.c b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> index 2aae636f1..0e70e27fd 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gpu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> @@ -228,6 +228,7 @@ static void panfrost_gpu_init_features(struct panfrost_device *pfdev)
> pfdev->features.thread_max_workgroup_sz = gpu_read(pfdev, GPU_THREAD_MAX_WORKGROUP_SIZE);
> pfdev->features.thread_max_barrier_sz = gpu_read(pfdev, GPU_THREAD_MAX_BARRIER_SIZE);
> pfdev->features.coherency_features = gpu_read(pfdev, GPU_COHERENCY_FEATURES);
> + pfdev->features.afbc_features = gpu_read(pfdev, GPU_AFBC_FEATURES);
> for (i = 0; i < 4; i++)
> pfdev->features.texture_features[i] = gpu_read(pfdev, GPU_TEXTURE_FEATURES(i));
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_regs.h b/drivers/gpu/drm/panfrost/panfrost_regs.h
> index eddaa62ad..dc9df5457 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_regs.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_regs.h
> @@ -82,6 +82,7 @@
>
> #define GPU_TEXTURE_FEATURES(n) (0x0B0 + ((n) * 4))
> #define GPU_JS_FEATURES(n) (0x0C0 + ((n) * 4))
> +#define GPU_AFBC_FEATURES (0x4C) /* (RO) AFBC support on Bifrost */
>
> #define GPU_SHADER_PRESENT_LO 0x100 /* (RO) Shader core present bitmap, low word */
> #define GPU_SHADER_PRESENT_HI 0x104 /* (RO) Shader core present bitmap, high word */
> diff --git a/include/uapi/drm/panfrost_drm.h b/include/uapi/drm/panfrost_drm.h
> index ec19db1ee..061e700dd 100644
> --- a/include/uapi/drm/panfrost_drm.h
> +++ b/include/uapi/drm/panfrost_drm.h
> @@ -171,6 +171,7 @@ enum drm_panfrost_param {
> DRM_PANFROST_PARAM_JS_FEATURES15,
> DRM_PANFROST_PARAM_NR_CORE_GROUPS,
> DRM_PANFROST_PARAM_THREAD_TLS_ALLOC,
> + DRM_PANFROST_PARAM_AFBC_FEATURES,
> };
>
> struct drm_panfrost_get_param {
>
