drm/ast: Turn ioregs_lock to modeset_lock

The lock for the I/O registers is only relevant during mode-setting
operations. It protects the registers from concurrent access from
reading EDID information.

Reduce lock coverage to mode setting, rename the lock and move it
entirely into the mode-setting code. No functional changes, as the
I/O lock was never used for anything else than mode setting.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231116100240.22975-2-tzimmermann@suse.de

drivers/gpu/drm/ast/ast_drv.h

@@ -192,7 +192,6 @@ to_ast_bmc_connector(struct drm_connector *connector)
 struct ast_device {
 	struct drm_device base;
 
-	struct mutex ioregs_lock; /* Protects access to I/O registers in ioregs */
 	void __iomem *regs;
 	void __iomem *ioregs;
 	void __iomem *dp501_fw_buf;
@@ -207,6 +206,8 @@ struct ast_device {
 	unsigned long	vram_size;
 	unsigned long	vram_fb_available;
 
+	struct mutex modeset_lock; /* Protects access to modeset I/O registers in ioregs */
+
 	struct ast_plane primary_plane;
 	struct ast_plane cursor_plane;
 	struct drm_crtc crtc;

drivers/gpu/drm/ast/ast_main.c

@@ -440,10 +440,6 @@ struct ast_device *ast_device_create(const struct drm_driver *drv,
 
 	pci_set_drvdata(pdev, dev);
 
-	ret = drmm_mutex_init(dev, &ast->ioregs_lock);
-	if (ret)
-		return ERR_PTR(ret);
-
 	ast->regs = pcim_iomap(pdev, 1, 0);
 	if (!ast->regs)
 		return ERR_PTR(-EIO);

drivers/gpu/drm/ast/ast_mode.c

@@ -1358,13 +1358,13 @@ static int ast_vga_connector_helper_get_modes(struct drm_connector *connector)
 	 * Protect access to I/O registers from concurrent modesetting
 	 * by acquiring the I/O-register lock.
 	 */
-	mutex_lock(&ast->ioregs_lock);
+	mutex_lock(&ast->modeset_lock);
 
 	edid = drm_get_edid(connector, &ast_vga_connector->i2c->adapter);
 	if (!edid)
 		goto err_mutex_unlock;
 
-	mutex_unlock(&ast->ioregs_lock);
+	mutex_unlock(&ast->modeset_lock);
 
 	count = drm_add_edid_modes(connector, edid);
 	kfree(edid);
@@ -1372,7 +1372,7 @@ static int ast_vga_connector_helper_get_modes(struct drm_connector *connector)
 	return count;
 
 err_mutex_unlock:
-	mutex_unlock(&ast->ioregs_lock);
+	mutex_unlock(&ast->modeset_lock);
 err_drm_connector_update_edid_property:
 	drm_connector_update_edid_property(connector, NULL);
 	return 0;
@@ -1464,13 +1464,13 @@ static int ast_sil164_connector_helper_get_modes(struct drm_connector *connector
 	 * Protect access to I/O registers from concurrent modesetting
 	 * by acquiring the I/O-register lock.
 	 */
-	mutex_lock(&ast->ioregs_lock);
+	mutex_lock(&ast->modeset_lock);
 
 	edid = drm_get_edid(connector, &ast_sil164_connector->i2c->adapter);
 	if (!edid)
 		goto err_mutex_unlock;
 
-	mutex_unlock(&ast->ioregs_lock);
+	mutex_unlock(&ast->modeset_lock);
 
 	count = drm_add_edid_modes(connector, edid);
 	kfree(edid);
@@ -1478,7 +1478,7 @@ static int ast_sil164_connector_helper_get_modes(struct drm_connector *connector
 	return count;
 
 err_mutex_unlock:
-	mutex_unlock(&ast->ioregs_lock);
+	mutex_unlock(&ast->modeset_lock);
 err_drm_connector_update_edid_property:
 	drm_connector_update_edid_property(connector, NULL);
 	return 0;
@@ -1670,13 +1670,13 @@ static int ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
 	 * Protect access to I/O registers from concurrent modesetting
 	 * by acquiring the I/O-register lock.
 	 */
-	mutex_lock(&ast->ioregs_lock);
+	mutex_lock(&ast->modeset_lock);
 
 	succ = ast_astdp_read_edid(connector->dev, edid);
 	if (succ < 0)
 		goto err_mutex_unlock;
 
-	mutex_unlock(&ast->ioregs_lock);
+	mutex_unlock(&ast->modeset_lock);
 
 	drm_connector_update_edid_property(connector, edid);
 	count = drm_add_edid_modes(connector, edid);
@@ -1685,7 +1685,7 @@ static int ast_astdp_connector_helper_get_modes(struct drm_connector *connector)
 	return count;
 
 err_mutex_unlock:
-	mutex_unlock(&ast->ioregs_lock);
+	mutex_unlock(&ast->modeset_lock);
 	kfree(edid);
 err_drm_connector_update_edid_property:
 	drm_connector_update_edid_property(connector, NULL);
@@ -1870,9 +1870,9 @@ static void ast_mode_config_helper_atomic_commit_tail(struct drm_atomic_state *s
 	 * display modes. Protect access to I/O registers by acquiring
 	 * the I/O-register lock. Released in atomic_flush().
 	 */
-	mutex_lock(&ast->ioregs_lock);
+	mutex_lock(&ast->modeset_lock);
 	drm_atomic_helper_commit_tail_rpm(state);
-	mutex_unlock(&ast->ioregs_lock);
+	mutex_unlock(&ast->modeset_lock);
 }
 
 static const struct drm_mode_config_helper_funcs ast_mode_config_helper_funcs = {
@@ -1910,6 +1910,10 @@ int ast_mode_config_init(struct ast_device *ast)
 	struct drm_connector *physical_connector = NULL;
 	int ret;
 
+	ret = drmm_mutex_init(dev, &ast->modeset_lock);
+	if (ret)
+		return ret;
+
 	ret = drmm_mode_config_init(dev);
 	if (ret)
 		return ret;