drm/mgag200: Acquire I/O lock while reading EDID

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 946965594140 ("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: 946965594140 ("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

diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index 73d5a4a42b3a023ea6c31b5476c5b1d8f79ab4ae..762b9657ae8d354c63fd8080415445101bc2607c 100644 (file)
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -691,16 +691,26 @@ 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;
 }