[PATCH 5.19 0310/1157] drm/mgag200: Acquire I/O lock while reading EDID

Greg Kroah-Hartman
2022-08-15T23:25:25Z

From: Thomas Zimmermann <tzimmermann@suse.de>

[ Upstream commit 5913ab941d6ea782e841234c76958c6872ea752d ]

DDC operation conflicts with concurrent mode setting. Acquire the
driver's I/O lock in get_modes to prevent this. This change should
have been part of commit 931e3f3a0e99 ("drm/mgag200: Protect
concurrent access to I/O registers with lock"), but apparently got
lost somewhere.

v3:
* fix commit message to say 'drm/mgag200' (Jocelyn)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 931e3f3a0e99 ("drm/mgag200: Protect concurrent access to I/O registers with lock")
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Tested-by: Jocelyn Falempe <jfalempe@redhat.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Jocelyn Falempe <jfalempe@redhat.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Cc: dri-devel@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/20220516134343.6085-2-tzimmermann@suse.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/mgag200/mgag200_mode.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index abde7655477d..4ad8d62c5631 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -667,16 +667,26 @@ static void mgag200_disable_display(struct mga_device *mdev)

static int mga_vga_get_modes(struct drm_connector *connector)
{
+ struct mga_device *mdev = to_mga_device(connector->dev);
struct mga_connector *mga_connector = to_mga_connector(connector);
struct edid *edid;
int ret = 0;

+ /*
+ * Protect access to I/O registers from concurrent modesetting
+ * by acquiring the I/O-register lock.
+ */
+ mutex_lock(&mdev->rmmio_lock);
+
edid = drm_get_edid(connector, &mga_connector->i2c->adapter);
if (edid) {
drm_connector_update_edid_property(connector, edid);
ret = drm_add_edid_modes(connector, edid);
kfree(edid);
}
+
+ mutex_unlock(&mdev->rmmio_lock);
+
return ret;
}

--
2.35.1