diff --git a/drivers/gpu/drm/mgag200/Kconfig b/drivers/gpu/drm/mgag200/Kconfig index b28c5e4828f47..5e4d48df4854c 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 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 0eb769dd76ce0..e17cb4c5f7741 100644 --- a/drivers/gpu/drm/mgag200/mgag200_mode.c +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c @@ -13,6 +13,7 @@ #include #include +#include #include #include #include @@ -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 } /*