Hi Am 27.01.22 um 12:42 schrieb Daniel Vetter:
On Thu, Jan 27, 2022 at 11:26:21AM +0100, Thomas Zimmermann wrote:Mark screen buffers in system memory with FB_VIRTFB. Otherwise, the buffers are mmap'ed as I/O memory (i.e., VM_IO). For shadow buffers, also set the FB_READS_FAST hint.Maybe clarify that this only holds for the defio case, and since we have our own shadow copy for that anyway it shouldn't matter. I'm also not sure how much the memcpy gains us compared to just redrawing ... What's the motivation here, or just something you spotted?
Correctness mostly. fbdev's fbdefio tests for (the absence of) this flag and sets VM_IO accordingly.
It's actually for userspace. Maybe userspace tests these flags as well and can optimize memcpy pattern for different types of caching. But I wouldn't expect it TBH.
Best regards Thomas
-DanielSigned-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx> --- drivers/gpu/drm/drm_fb_helper.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index ed43b987d306..f15127a32f7a 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -2346,6 +2346,7 @@ static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper, fbi->fbops = &drm_fbdev_fb_ops; fbi->screen_size = sizes->surface_height * fb->pitches[0]; fbi->fix.smem_len = fbi->screen_size; + fbi->flags = FBINFO_DEFAULT;drm_fb_helper_fill_info(fbi, fb_helper, sizes); @@ -2353,19 +2354,21 @@ static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,fbi->screen_buffer = vzalloc(fbi->screen_size); if (!fbi->screen_buffer) return -ENOMEM; + fbi->flags |= FBINFO_VIRTFB | FBINFO_READS_FAST;fbi->fbdefio = &drm_fbdev_defio;- fb_deferred_io_init(fbi); } else { /* buffer is mapped for HW framebuffer */ ret = drm_client_buffer_vmap(fb_helper->buffer, &map); if (ret) return ret; - if (map.is_iomem) + if (map.is_iomem) { fbi->screen_base = map.vaddr_iomem; - else + } else { fbi->screen_buffer = map.vaddr; + fbi->flags |= FBINFO_VIRTFB; + }/** Shamelessly leak the physical address to user-space. As -- 2.34.1
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev
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