linux-kernel - [PATCH] drm/ssd130x: Synchronize access to dma-buf imported GEM BOs

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Message-Id: <20220927095249.1919385-1-javierm@redhat.com>
Date:   Tue, 27 Sep 2022 11:52:49 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Zimmermann <tzimmermann@...e.de>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH] drm/ssd130x: Synchronize access to dma-buf imported GEM BOs

Synchronize CPU access to GEM BOs with other drivers when updating the
screen buffer. Imported DMA buffers might otherwise contain stale data.

Suggested-by: Thomas Zimmermann <tzimmermann@...e.de>
Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
---

 drivers/gpu/drm/solomon/ssd130x.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/solomon/ssd130x.c b/drivers/gpu/drm/solomon/ssd130x.c
index a537692100d1..bc41a5ae810a 100644
--- a/drivers/gpu/drm/solomon/ssd130x.c
+++ b/drivers/gpu/drm/solomon/ssd130x.c
@@ -555,11 +555,18 @@ static int ssd130x_fb_blit_rect(struct drm_framebuffer *fb, const struct iosys_m
 	if (!buf)
 		return -ENOMEM;
 
+	ret = drm_gem_fb_begin_cpu_access(fb, DMA_FROM_DEVICE);
+	if (ret)
+		goto out_free;
+
 	iosys_map_set_vaddr(&dst, buf);
 	drm_fb_xrgb8888_to_mono(&dst, &dst_pitch, vmap, fb, rect);
 
+	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
+
 	ssd130x_update_rect(ssd130x, buf, rect);
 
+out_free:
 	kfree(buf);
 
 	return ret;
-- 
2.37.3