diff options
Diffstat (limited to 'drivers/gpu/drm/mgag200')
| -rw-r--r-- | drivers/gpu/drm/mgag200/Kconfig | 12 | ||||
| -rw-r--r-- | drivers/gpu/drm/mgag200/mgag200_drv.c | 17 | ||||
| -rw-r--r-- | drivers/gpu/drm/mgag200/mgag200_mode.c | 8 |
3 files changed, 37 insertions, 0 deletions
diff --git a/drivers/gpu/drm/mgag200/Kconfig b/drivers/gpu/drm/mgag200/Kconfig index b28c5e4828f4..5e4d48df4854 100644 --- a/drivers/gpu/drm/mgag200/Kconfig +++ b/drivers/gpu/drm/mgag200/Kconfig @@ -11,3 +11,15 @@ 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 54fce00e2136..573dbe256aa8 100644 --- a/drivers/gpu/drm/mgag200/mgag200_drv.c +++ b/drivers/gpu/drm/mgag200/mgag200_drv.c @@ -84,6 +84,20 @@ 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 */ @@ -99,6 +113,9 @@ 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 0eb769dd76ce..e17cb4c5f774 100644 --- a/drivers/gpu/drm/mgag200/mgag200_mode.c +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c @@ -13,6 +13,7 @@ #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> @@ -436,6 +437,13 @@ 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 } /* |