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drm/panfrost: Add AFBC_FEATURES parameter

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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!

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 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.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210604130011.3203-1-alyssa.rosenzweig@collabora.com
This commit is contained in:
Alyssa Rosenzweig 2021-06-04 09:00:11 -04:00 committed by Steven Price
parent cb1c81467a
commit 3e2926f875
5 changed files with 7 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

1
drivers/gpu/drm/panfrost/panfrost_device.h
View file

@ -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];

4
drivers/gpu/drm/panfrost/panfrost_drv.c
View file

@ -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);
@ -547,6 +548,7 @@ DEFINE_DRM_GEM_FOPS(panfrost_drm_driver_fops);
* Panfrost driver version:
* - 1.0 - initial interface
* - 1.1 - adds HEAP and NOEXEC flags for CREATE_BO
* - 1.2 - adds AFBC_FEATURES query
*/
static const struct drm_driver panfrost_drm_driver = {
.driver_features = DRIVER_RENDER | DRIVER_GEM | DRIVER_SYNCOBJ,
@ -559,7 +561,7 @@ static const struct drm_driver panfrost_drm_driver = {
.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,

1
drivers/gpu/drm/panfrost/panfrost_gpu.c
View file

@ -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));

1
drivers/gpu/drm/panfrost/panfrost_regs.h
View file

@ -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 */

1
include/uapi/drm/panfrost_drm.h
View file

@ -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 {