On Tue, Mar 4, 2025 at 4:41 PM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote:
>
> Hi
>
> Am 04.03.25 um 07:33 schrieb Huacai Chen:
> > Commit f2fa5a99ca81ce105653 ("drm/ast: Convert ast to SHMEM") converts
> > ast from VRAM helper to SHMEM helper. The convertion makesast support
> > higher display resolutions, but the performance decreases significantly
> > on platforms which don't support writecombine (fallback to uncached).
> >
> > This patch implements both SHMEM helper and VRAM helper for ast driver
> > at the same time. A module parameter ast.shmem is added, 1 means SHMEM
> > hepler, 0 means VRAM helper, and the default (-1) means auto selection
> > according to drm_arch_can_wc_memory().
>
> Sorry won't happen. There's one memory manager and that's it.
>
> The question is why there is a difference between the two. Because
> conceptually, it's both software rendering that copies the final image
> into video ram. Why is that much faster with VRAM helpers?
Correct me if I'm wrong.
SHMEM helper means "copy damage data to a fixed VRAM buffer", VRAM
helper means "double buffers and swapping the two". So if WC is not
supported, SHMEM helper is slower from visible effect.
Huacai
>
> Best regards
> Thomas
>
> >
> > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/ast/Kconfig | 3 +
> > drivers/gpu/drm/ast/ast_drv.c | 31 ++++++++--
> > drivers/gpu/drm/ast/ast_drv.h | 6 +-
> > drivers/gpu/drm/ast/ast_mm.c | 11 +++-
> > drivers/gpu/drm/ast/ast_mode.c | 105 +++++++++++++++++++++++++--------
> > 5 files changed, 124 insertions(+), 32 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ast/Kconfig b/drivers/gpu/drm/ast/Kconfig
> > index da0663542e8a..ed07ef70072f 100644
> > --- a/drivers/gpu/drm/ast/Kconfig
> > +++ b/drivers/gpu/drm/ast/Kconfig
> > @@ -5,6 +5,9 @@ config DRM_AST
> > select DRM_CLIENT_SELECTION
> > select DRM_GEM_SHMEM_HELPER
> > select DRM_KMS_HELPER
> > + select DRM_TTM
> > + select DRM_TTM_HELPER
> > + select DRM_VRAM_HELPER
> > select I2C
> > select I2C_ALGOBIT
> > help
> > diff --git a/drivers/gpu/drm/ast/ast_drv.c b/drivers/gpu/drm/ast/ast_drv.c
> > index ff3bcdd1cff2..a0c693844f1e 100644
> > --- a/drivers/gpu/drm/ast/ast_drv.c
> > +++ b/drivers/gpu/drm/ast/ast_drv.c
> > @@ -33,9 +33,12 @@
> >
> > #include <drm/clients/drm_client_setup.h>
> > #include <drm/drm_atomic_helper.h>
> > +#include <drm/drm_cache.h>
> > #include <drm/drm_drv.h>
> > #include <drm/drm_fbdev_shmem.h>
> > +#include <drm/drm_fbdev_ttm.h>
> > #include <drm/drm_gem_shmem_helper.h>
> > +#include <drm/drm_gem_vram_helper.h>
> > #include <drm/drm_module.h>
> > #include <drm/drm_probe_helper.h>
> >
> > @@ -46,13 +49,18 @@ static int ast_modeset = -1;
> > MODULE_PARM_DESC(modeset, "Disable/Enable modesetting");
> > module_param_named(modeset, ast_modeset, int, 0400);
> >
> > +int ast_shmem = -1;
> > +
> > +MODULE_PARM_DESC(shmem, "1 = SHMEM helper, 0 = VRAM helper, -1 = Auto");
> > +module_param_named(shmem, ast_shmem, int, 0400);
> > +
> > /*
> > * DRM driver
> > */
> >
> > DEFINE_DRM_GEM_FOPS(ast_fops);
> >
> > -static const struct drm_driver ast_driver = {
> > +static struct drm_driver ast_driver = {
> > .driver_features = DRIVER_ATOMIC |
> > DRIVER_GEM |
> > DRIVER_MODESET,
> > @@ -63,9 +71,6 @@ static const struct drm_driver ast_driver = {
> > .major = DRIVER_MAJOR,
> > .minor = DRIVER_MINOR,
> > .patchlevel = DRIVER_PATCHLEVEL,
> > -
> > - DRM_GEM_SHMEM_DRIVER_OPS,
> > - DRM_FBDEV_SHMEM_DRIVER_OPS,
> > };
> >
> > /*
> > @@ -280,6 +285,24 @@ static int ast_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> > struct drm_device *drm;
> > bool need_post = false;
> >
> > + if (ast_shmem == -1)
> > + ast_shmem = drm_arch_can_wc_memory() ? 1 : 0;
> > +
> > + if (ast_shmem) {
> > + ast_driver.dumb_create = drm_gem_shmem_dumb_create;
> > + ast_driver.gem_prime_import_sg_table = drm_gem_shmem_prime_import_sg_table;
> > +#ifdef CONFIG_DRM_FBDEV_EMULATION
> > + ast_driver.fbdev_probe = drm_fbdev_shmem_driver_fbdev_probe;
> > +#endif
> > + } else {
> > + ast_driver.dumb_create = drm_gem_vram_driver_dumb_create;
> > + ast_driver.dumb_map_offset = drm_gem_ttm_dumb_map_offset;
> > + ast_driver.debugfs_init = drm_vram_mm_debugfs_init;
> > +#ifdef CONFIG_DRM_FBDEV_EMULATION
> > + ast_driver.fbdev_probe = drm_fbdev_ttm_driver_fbdev_probe;
> > +#endif
> > + }
> > +
> > ret = aperture_remove_conflicting_pci_devices(pdev, ast_driver.name);
> > if (ret)
> > return ret;
> > diff --git a/drivers/gpu/drm/ast/ast_drv.h b/drivers/gpu/drm/ast/ast_drv.h
> > index 6b4305ac07d4..3fcf6717ad8a 100644
> > --- a/drivers/gpu/drm/ast/ast_drv.h
> > +++ b/drivers/gpu/drm/ast/ast_drv.h
> > @@ -29,6 +29,7 @@
> > #define __AST_DRV_H__
> >
> > #include <linux/io.h>
> > +#include <linux/iosys-map.h>
> > #include <linux/types.h>
> >
> > #include <drm/drm_connector.h>
> > @@ -53,6 +54,8 @@
> >
> > #define __AST_CHIP(__gen, __index) ((__gen) << 16 | (__index))
> >
> > +extern int ast_shmem;
> > +
> > enum ast_chip {
> > /* 1st gen */
> > AST1000 = __AST_CHIP(1, 0), // unused
> > @@ -130,7 +133,8 @@ enum ast_config_mode {
> > struct ast_plane {
> > struct drm_plane base;
> >
> > - void __iomem *vaddr;
> > + struct drm_gem_vram_object *gbo;
> > + struct iosys_map map;
> > u64 offset;
> > unsigned long size;
> > };
> > diff --git a/drivers/gpu/drm/ast/ast_mm.c b/drivers/gpu/drm/ast/ast_mm.c
> > index 6dfe6d9777d4..588326b7d53e 100644
> > --- a/drivers/gpu/drm/ast/ast_mm.c
> > +++ b/drivers/gpu/drm/ast/ast_mm.c
> > @@ -28,6 +28,7 @@
> >
> > #include <linux/pci.h>
> >
> > +#include <drm/drm_gem_vram_helper.h>
> > #include <drm/drm_managed.h>
> > #include <drm/drm_print.h>
> >
> > @@ -87,9 +88,13 @@ int ast_mm_init(struct ast_device *ast)
> >
> > vram_size = ast_get_vram_size(ast);
> >
> > - ast->vram = devm_ioremap_wc(dev->dev, base, vram_size);
> > - if (!ast->vram)
> > - return -ENOMEM;
> > + if (!ast_shmem)
> > + drmm_vram_helper_init(dev, base, vram_size);
> > + else {
> > + ast->vram = devm_ioremap_wc(dev->dev, base, vram_size);
> > + if (!ast->vram)
> > + return -ENOMEM;
> > + }
> >
> > ast->vram_base = base;
> > ast->vram_size = vram_size;
> > diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
> > index 9d5321c81e68..0744d1ac5dfb 100644
> > --- a/drivers/gpu/drm/ast/ast_mode.c
> > +++ b/drivers/gpu/drm/ast/ast_mode.c
> > @@ -41,6 +41,7 @@
> > #include <drm/drm_gem_atomic_helper.h>
> > #include <drm/drm_gem_framebuffer_helper.h>
> > #include <drm/drm_gem_shmem_helper.h>
> > +#include <drm/drm_gem_vram_helper.h>
> > #include <drm/drm_managed.h>
> > #include <drm/drm_panic.h>
> > #include <drm/drm_probe_helper.h>
> > @@ -566,8 +567,7 @@ static void ast_wait_for_vretrace(struct ast_device *ast)
> > */
> >
> > static int ast_plane_init(struct drm_device *dev, struct ast_plane *ast_plane,
> > - void __iomem *vaddr, u64 offset, unsigned long size,
> > - uint32_t possible_crtcs,
> > + u64 offset, unsigned long size, uint32_t possible_crtcs,
> > const struct drm_plane_funcs *funcs,
> > const uint32_t *formats, unsigned int format_count,
> > const uint64_t *format_modifiers,
> > @@ -575,7 +575,6 @@ static int ast_plane_init(struct drm_device *dev, struct ast_plane *ast_plane,
> > {
> > struct drm_plane *plane = &ast_plane->base;
> >
> > - ast_plane->vaddr = vaddr;
> > ast_plane->offset = offset;
> > ast_plane->size = size;
> >
> > @@ -630,7 +629,7 @@ static void ast_handle_damage(struct ast_plane *ast_plane, struct iosys_map *src
> > struct drm_framebuffer *fb,
> > const struct drm_rect *clip)
> > {
> > - struct iosys_map dst = IOSYS_MAP_INIT_VADDR_IOMEM(ast_plane->vaddr);
> > + struct iosys_map dst = ast_plane->map;
> >
> > iosys_map_incr(&dst, drm_fb_clip_offset(fb->pitches[0], fb->format, clip));
> > drm_fb_memcpy(&dst, fb->pitches, src, fb, clip);
> > @@ -650,6 +649,7 @@ static void ast_primary_plane_helper_atomic_update(struct drm_plane *plane,
> > struct drm_crtc *crtc = plane_state->crtc;
> > struct drm_crtc_state *crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
> > struct drm_rect damage;
> > + struct drm_gem_vram_object *gbo;
> > struct drm_atomic_helper_damage_iter iter;
> >
> > if (!old_fb || (fb->format != old_fb->format) || crtc_state->mode_changed) {
> > @@ -660,9 +660,15 @@ static void ast_primary_plane_helper_atomic_update(struct drm_plane *plane,
> > ast_set_vbios_color_reg(ast, fb->format, vbios_mode_info);
> > }
> >
> > - drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
> > - drm_atomic_for_each_plane_damage(&iter, &damage) {
> > - ast_handle_damage(ast_plane, shadow_plane_state->data, fb, &damage);
> > + if (!ast_shmem) {
> > + gbo = drm_gem_vram_of_gem(fb->obj[0]);
> > + ast_plane->offset = drm_gem_vram_offset(gbo);
> > + ast_set_start_address_crt1(ast, (u32)ast_plane->offset);
> > + } else {
> > + drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
> > + drm_atomic_for_each_plane_damage(&iter, &damage) {
> > + ast_handle_damage(ast_plane, shadow_plane_state->data, fb, &damage);
> > + }
> > }
> >
> > /*
> > @@ -704,19 +710,18 @@ static int ast_primary_plane_helper_get_scanout_buffer(struct drm_plane *plane,
> > {
> > struct ast_plane *ast_plane = to_ast_plane(plane);
> >
> > - if (plane->state && plane->state->fb && ast_plane->vaddr) {
> > + if (plane->state && plane->state->fb && ast_plane->map.vaddr_iomem) {
> > sb->format = plane->state->fb->format;
> > sb->width = plane->state->fb->width;
> > sb->height = plane->state->fb->height;
> > sb->pitch[0] = plane->state->fb->pitches[0];
> > - iosys_map_set_vaddr_iomem(&sb->map[0], ast_plane->vaddr);
> > + iosys_map_set_vaddr_iomem(&sb->map[0], ast_plane->map.vaddr_iomem);
> > return 0;
> > }
> > return -ENODEV;
> > }
> >
> > -static const struct drm_plane_helper_funcs ast_primary_plane_helper_funcs = {
> > - DRM_GEM_SHADOW_PLANE_HELPER_FUNCS,
> > +static struct drm_plane_helper_funcs ast_primary_plane_helper_funcs = {
> > .atomic_check = ast_primary_plane_helper_atomic_check,
> > .atomic_update = ast_primary_plane_helper_atomic_update,
> > .atomic_enable = ast_primary_plane_helper_atomic_enable,
> > @@ -724,11 +729,10 @@ static const struct drm_plane_helper_funcs ast_primary_plane_helper_funcs = {
> > .get_scanout_buffer = ast_primary_plane_helper_get_scanout_buffer,
> > };
> >
> > -static const struct drm_plane_funcs ast_primary_plane_funcs = {
> > +static struct drm_plane_funcs ast_primary_plane_funcs = {
> > .update_plane = drm_atomic_helper_update_plane,
> > .disable_plane = drm_atomic_helper_disable_plane,
> > .destroy = drm_plane_cleanup,
> > - DRM_GEM_SHADOW_PLANE_FUNCS,
> > };
> >
> > static int ast_primary_plane_init(struct ast_device *ast)
> > @@ -737,12 +741,28 @@ static int ast_primary_plane_init(struct ast_device *ast)
> > struct ast_plane *ast_primary_plane = &ast->primary_plane;
> > struct drm_plane *primary_plane = &ast_primary_plane->base;
> > void __iomem *vaddr = ast->vram;
> > - u64 offset = 0; /* with shmem, the primary plane is always at offset 0 */
> > + u64 offset = 0; /* the primary plane is initially at offset 0 */
> > unsigned long cursor_size = roundup(AST_HWC_SIZE + AST_HWC_SIGNATURE_SIZE, PAGE_SIZE);
> > unsigned long size = ast->vram_fb_available - cursor_size;
> > int ret;
> >
> > - ret = ast_plane_init(dev, ast_primary_plane, vaddr, offset, size,
> > + if (ast_shmem) {
> > + ast_primary_plane_funcs.reset = drm_gem_reset_shadow_plane;
> > + ast_primary_plane_funcs.atomic_duplicate_state = drm_gem_duplicate_shadow_plane_state;
> > + ast_primary_plane_funcs.atomic_destroy_state = drm_gem_destroy_shadow_plane_state;
> > + ast_primary_plane_helper_funcs.begin_fb_access = drm_gem_begin_shadow_fb_access;
> > + ast_primary_plane_helper_funcs.end_fb_access = drm_gem_end_shadow_fb_access;
> > + } else {
> > + ast_primary_plane_funcs.reset = drm_atomic_helper_plane_reset;
> > + ast_primary_plane_funcs.atomic_duplicate_state = drm_atomic_helper_plane_duplicate_state;
> > + ast_primary_plane_funcs.atomic_destroy_state = drm_atomic_helper_plane_destroy_state;
> > + ast_primary_plane_helper_funcs.prepare_fb = drm_gem_vram_plane_helper_prepare_fb;
> > + ast_primary_plane_helper_funcs.cleanup_fb = drm_gem_vram_plane_helper_cleanup_fb;
> > + }
> > +
> > + iosys_map_set_vaddr_iomem(&ast_primary_plane->map, vaddr);
> > +
> > + ret = ast_plane_init(dev, ast_primary_plane, offset, size,
> > 0x01, &ast_primary_plane_funcs,
> > ast_primary_plane_formats, ARRAY_SIZE(ast_primary_plane_formats),
> > NULL, DRM_PLANE_TYPE_PRIMARY);
> > @@ -902,10 +922,11 @@ static void ast_cursor_plane_helper_atomic_update(struct drm_plane *plane,
> > struct drm_plane_state *old_plane_state = drm_atomic_get_old_plane_state(state, plane);
> > struct ast_device *ast = to_ast_device(plane->dev);
> > struct iosys_map src_map = shadow_plane_state->data[0];
> > + struct iosys_map dst_map = ast_plane->map;
> > struct drm_rect damage;
> > const u8 *src = src_map.vaddr; /* TODO: Use mapping abstraction properly */
> > u64 dst_off = ast_plane->offset;
> > - u8 __iomem *dst = ast_plane->vaddr; /* TODO: Use mapping abstraction properly */
> > + u8 __iomem *dst = dst_map.vaddr_iomem; /* TODO: Use mapping abstraction properly */
> > u8 __iomem *sig = dst + AST_HWC_SIZE; /* TODO: Use mapping abstraction properly */
> > unsigned int offset_x, offset_y;
> > u16 x, y;
> > @@ -967,10 +988,22 @@ static const struct drm_plane_helper_funcs ast_cursor_plane_helper_funcs = {
> > .atomic_disable = ast_cursor_plane_helper_atomic_disable,
> > };
> >
> > -static const struct drm_plane_funcs ast_cursor_plane_funcs = {
> > +static void ast_cursor_plane_destroy(struct drm_plane *plane)
> > +{
> > + struct ast_plane *ast_plane = to_ast_plane(plane);
> > + struct drm_gem_vram_object *gbo = ast_plane->gbo;
> > + struct iosys_map map = ast_plane->map;
> > +
> > + drm_gem_vram_vunmap(gbo, &map);
> > + drm_gem_vram_unpin(gbo);
> > + drm_gem_vram_put(gbo);
> > +
> > + drm_plane_cleanup(plane);
> > +}
> > +
> > +static struct drm_plane_funcs ast_cursor_plane_funcs = {
> > .update_plane = drm_atomic_helper_update_plane,
> > .disable_plane = drm_atomic_helper_disable_plane,
> > - .destroy = drm_plane_cleanup,
> > DRM_GEM_SHADOW_PLANE_FUNCS,
> > };
> >
> > @@ -979,6 +1012,8 @@ static int ast_cursor_plane_init(struct ast_device *ast)
> > struct drm_device *dev = &ast->base;
> > struct ast_plane *ast_cursor_plane = &ast->cursor_plane;
> > struct drm_plane *cursor_plane = &ast_cursor_plane->base;
> > + struct drm_gem_vram_object *gbo;
> > + struct iosys_map map;
> > size_t size;
> > void __iomem *vaddr;
> > u64 offset;
> > @@ -994,10 +1029,25 @@ static int ast_cursor_plane_init(struct ast_device *ast)
> > if (ast->vram_fb_available < size)
> > return -ENOMEM;
> >
> > - vaddr = ast->vram + ast->vram_fb_available - size;
> > - offset = ast->vram_fb_available - size;
> > + if (ast_shmem) {
> > + vaddr = ast->vram + ast->vram_fb_available - size;
> > + offset = ast->vram_fb_available - size;
> > + iosys_map_set_vaddr_iomem(&ast_cursor_plane->map, vaddr);
> > + ast_cursor_plane_funcs.destroy = drm_plane_cleanup;
> > + } else {
> > + gbo = drm_gem_vram_create(dev, size, 0);
> > + if (IS_ERR(gbo))
> > + return PTR_ERR(gbo);
> > +
> > + drm_gem_vram_pin(gbo, DRM_GEM_VRAM_PL_FLAG_VRAM | DRM_GEM_VRAM_PL_FLAG_TOPDOWN);
> > + drm_gem_vram_vmap(gbo, &map);
> > + offset = drm_gem_vram_offset(gbo);
> > + ast_cursor_plane->gbo = gbo;
> > + ast_cursor_plane->map = map;
> > + ast_cursor_plane_funcs.destroy = ast_cursor_plane_destroy;
> > + }
> >
> > - ret = ast_plane_init(dev, ast_cursor_plane, vaddr, offset, size,
> > + ret = ast_plane_init(dev, ast_cursor_plane, offset, size,
> > 0x01, &ast_cursor_plane_funcs,
> > ast_cursor_plane_formats, ARRAY_SIZE(ast_cursor_plane_formats),
> > NULL, DRM_PLANE_TYPE_CURSOR);
> > @@ -1348,9 +1398,7 @@ static enum drm_mode_status ast_mode_config_mode_valid(struct drm_device *dev,
> > return MODE_OK;
> > }
> >
> > -static const struct drm_mode_config_funcs ast_mode_config_funcs = {
> > - .fb_create = drm_gem_fb_create_with_dirty,
> > - .mode_valid = ast_mode_config_mode_valid,
> > +static struct drm_mode_config_funcs ast_mode_config_funcs = {
> > .atomic_check = drm_atomic_helper_check,
> > .atomic_commit = drm_atomic_helper_commit,
> > };
> > @@ -1372,6 +1420,15 @@ int ast_mode_config_init(struct ast_device *ast)
> > dev->mode_config.min_width = 0;
> > dev->mode_config.min_height = 0;
> > dev->mode_config.preferred_depth = 24;
> > + dev->mode_config.prefer_shadow = !ast_shmem;
> > +
> > + if (!ast_shmem) {
> > + ast_mode_config_funcs.fb_create = drm_gem_fb_create;
> > + ast_mode_config_funcs.mode_valid = drm_vram_helper_mode_valid;
> > + } else {
> > + ast_mode_config_funcs.fb_create = drm_gem_fb_create_with_dirty;
> > + ast_mode_config_funcs.mode_valid = ast_mode_config_mode_valid;
> > + }
> >
> > if (ast->chip == AST2100 || // GEN2, but not AST1100 (?)
> > ast->chip == AST2200 || // GEN3, but not AST2150 (?)
>
> --
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Frankenstrasse 146, 90461 Nuernberg, Germany
> GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
> HRB 36809 (AG Nuernberg)
>
