| Message ID | 20240516161751.479558-2-jfalempe@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | drm/mgag200: Add an option to disable Write-Combine | expand |
Am 16.05.24 um 18:17 schrieb Jocelyn Falempe: > This reverts commit bfa4437fd3938ae2e186e7664b2db65bb8775670. > > This workaround doesn't work reliably on all servers. > I'll replace it with an option to disable Write-Combine, > which has more impact on performance, but fix the latency > issue on all hardware. > > Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com> Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de> > --- > drivers/gpu/drm/mgag200/Kconfig | 12 ------------ > drivers/gpu/drm/mgag200/mgag200_drv.c | 17 ----------------- > drivers/gpu/drm/mgag200/mgag200_mode.c | 8 -------- > 3 files changed, 37 deletions(-) > > diff --git a/drivers/gpu/drm/mgag200/Kconfig b/drivers/gpu/drm/mgag200/Kconfig > index 5e4d48df4854c..b28c5e4828f47 100644 > --- a/drivers/gpu/drm/mgag200/Kconfig > +++ b/drivers/gpu/drm/mgag200/Kconfig > @@ -11,15 +11,3 @@ config DRM_MGAG200 > MGA G200 desktop chips and the server variants. It requires 0.3.0 > of the modesetting userspace driver, and a version of mga driver > that will fail on KMS enabled devices. > - > -config DRM_MGAG200_IOBURST_WORKAROUND > - bool "Disable buffer caching" > - depends on DRM_MGAG200 && PREEMPT_RT && X86 > - help > - Enable a workaround to avoid I/O bursts within the mgag200 driver at > - the expense of overall display performance. > - It restores the <v5.10 behavior, by mapping the framebuffer in system > - RAM as Write-Combining, and flushing the cache after each write. > - This is only useful on x86_64 if you want to run processes with > - deterministic latency. > - If unsure, say N. > diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c b/drivers/gpu/drm/mgag200/mgag200_drv.c > index 65f2ed18b31c5..3883f25ca4d8b 100644 > --- a/drivers/gpu/drm/mgag200/mgag200_drv.c > +++ b/drivers/gpu/drm/mgag200/mgag200_drv.c > @@ -84,20 +84,6 @@ resource_size_t mgag200_probe_vram(void __iomem *mem, resource_size_t size) > return offset - 65536; > } > > -#if defined(CONFIG_DRM_MGAG200_IOBURST_WORKAROUND) > -static struct drm_gem_object *mgag200_create_object(struct drm_device *dev, size_t size) > -{ > - struct drm_gem_shmem_object *shmem; > - > - shmem = kzalloc(sizeof(*shmem), GFP_KERNEL); > - if (!shmem) > - return NULL; > - > - shmem->map_wc = true; > - return &shmem->base; > -} > -#endif > - > /* > * DRM driver > */ > @@ -113,9 +99,6 @@ static const struct drm_driver mgag200_driver = { > .major = DRIVER_MAJOR, > .minor = DRIVER_MINOR, > .patchlevel = DRIVER_PATCHLEVEL, > -#if defined(CONFIG_DRM_MGAG200_IOBURST_WORKAROUND) > - .gem_create_object = mgag200_create_object, > -#endif > DRM_GEM_SHMEM_DRIVER_OPS, > }; > > diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c > index fc54851d3384d..d3d820f7a77d7 100644 > --- a/drivers/gpu/drm/mgag200/mgag200_mode.c > +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c > @@ -13,7 +13,6 @@ > > #include <drm/drm_atomic.h> > #include <drm/drm_atomic_helper.h> > -#include <drm/drm_cache.h> > #include <drm/drm_damage_helper.h> > #include <drm/drm_edid.h> > #include <drm/drm_format_helper.h> > @@ -438,13 +437,6 @@ static void mgag200_handle_damage(struct mga_device *mdev, const struct iosys_ma > > iosys_map_incr(&dst, drm_fb_clip_offset(fb->pitches[0], fb->format, clip)); > drm_fb_memcpy(&dst, fb->pitches, vmap, fb, clip); > - > - /* Flushing the cache greatly improves latency on x86_64 */ > -#if defined(CONFIG_DRM_MGAG200_IOBURST_WORKAROUND) > - if (!vmap->is_iomem) > - drm_clflush_virt_range(vmap->vaddr + clip->y1 * fb->pitches[0], > - drm_rect_height(clip) * fb->pitches[0]); > -#endif > } > > /*
diff --git a/drivers/gpu/drm/mgag200/Kconfig b/drivers/gpu/drm/mgag200/Kconfig index 5e4d48df4854c..b28c5e4828f47 100644 --- a/drivers/gpu/drm/mgag200/Kconfig +++ b/drivers/gpu/drm/mgag200/Kconfig @@ -11,15 +11,3 @@ config DRM_MGAG200 MGA G200 desktop chips and the server variants. It requires 0.3.0 of the modesetting userspace driver, and a version of mga driver that will fail on KMS enabled devices. - -config DRM_MGAG200_IOBURST_WORKAROUND - bool "Disable buffer caching" - depends on DRM_MGAG200 && PREEMPT_RT && X86 - help - Enable a workaround to avoid I/O bursts within the mgag200 driver at - the expense of overall display performance. - It restores the <v5.10 behavior, by mapping the framebuffer in system - RAM as Write-Combining, and flushing the cache after each write. - This is only useful on x86_64 if you want to run processes with - deterministic latency. - If unsure, say N. diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c b/drivers/gpu/drm/mgag200/mgag200_drv.c index 65f2ed18b31c5..3883f25ca4d8b 100644 --- a/drivers/gpu/drm/mgag200/mgag200_drv.c +++ b/drivers/gpu/drm/mgag200/mgag200_drv.c @@ -84,20 +84,6 @@ resource_size_t mgag200_probe_vram(void __iomem *mem, resource_size_t size) return offset - 65536; } -#if defined(CONFIG_DRM_MGAG200_IOBURST_WORKAROUND) -static struct drm_gem_object *mgag200_create_object(struct drm_device *dev, size_t size) -{ - struct drm_gem_shmem_object *shmem; - - shmem = kzalloc(sizeof(*shmem), GFP_KERNEL); - if (!shmem) - return NULL; - - shmem->map_wc = true; - return &shmem->base; -} -#endif - /* * DRM driver */ @@ -113,9 +99,6 @@ static const struct drm_driver mgag200_driver = { .major = DRIVER_MAJOR, .minor = DRIVER_MINOR, .patchlevel = DRIVER_PATCHLEVEL, -#if defined(CONFIG_DRM_MGAG200_IOBURST_WORKAROUND) - .gem_create_object = mgag200_create_object, -#endif DRM_GEM_SHMEM_DRIVER_OPS, }; diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c index fc54851d3384d..d3d820f7a77d7 100644 --- a/drivers/gpu/drm/mgag200/mgag200_mode.c +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c @@ -13,7 +13,6 @@ #include <drm/drm_atomic.h> #include <drm/drm_atomic_helper.h> -#include <drm/drm_cache.h> #include <drm/drm_damage_helper.h> #include <drm/drm_edid.h> #include <drm/drm_format_helper.h> @@ -438,13 +437,6 @@ static void mgag200_handle_damage(struct mga_device *mdev, const struct iosys_ma iosys_map_incr(&dst, drm_fb_clip_offset(fb->pitches[0], fb->format, clip)); drm_fb_memcpy(&dst, fb->pitches, vmap, fb, clip); - - /* Flushing the cache greatly improves latency on x86_64 */ -#if defined(CONFIG_DRM_MGAG200_IOBURST_WORKAROUND) - if (!vmap->is_iomem) - drm_clflush_virt_range(vmap->vaddr + clip->y1 * fb->pitches[0], - drm_rect_height(clip) * fb->pitches[0]); -#endif } /*
This reverts commit bfa4437fd3938ae2e186e7664b2db65bb8775670. This workaround doesn't work reliably on all servers. I'll replace it with an option to disable Write-Combine, which has more impact on performance, but fix the latency issue on all hardware. Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com> --- drivers/gpu/drm/mgag200/Kconfig | 12 ------------ drivers/gpu/drm/mgag200/mgag200_drv.c | 17 ----------------- drivers/gpu/drm/mgag200/mgag200_mode.c | 8 -------- 3 files changed, 37 deletions(-)