[PATCH 09/10] drm/mgag200: Acquire I/O-register lock in DDC code

[Thomas Zimmermann]

The modeset lock protects the DDC code from concurrent modeset
operations, which use the same registers. Move that code from the
connector helpers into the DDC helpers .pre_xfer() and .post_xfer().

Both, .pre_xfer() and .post_xfer(), enclose the transfer of data blocks
over the I2C channel in the internal I2C function bit_xfer(). Both
calls are executed unconditionally if present. Invoking DDC transfers
from any where within the driver now takes the lock.

Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
---
 drivers/gpu/drm/mgag200/mgag200_ddc.c  | 24 ++++++++++++++++++++++++
 drivers/gpu/drm/mgag200/mgag200_mode.c |  9 ---------
 2 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/mgag200/mgag200_ddc.c 
b/drivers/gpu/drm/mgag200/mgag200_ddc.c
index 3fa11b190943e..6d81ea8931e88 100644
--- a/drivers/gpu/drm/mgag200/mgag200_ddc.c
+++ b/drivers/gpu/drm/mgag200/mgag200_ddc.c
@@ -99,6 +99,28 @@ static int mgag200_ddc_algo_bit_data_getscl(void *data)
        return (mga_i2c_read_gpio(ddc->mdev) & ddc->clock) ? 1 : 0;
 }
 
+static int mgag200_ddc_algo_bit_data_pre_xfer(struct i2c_adapter *adapter)
+{
+       struct mgag200_ddc *ddc = i2c_get_adapdata(adapter);
+       struct mga_device *mdev = ddc->mdev;
+
+       /*
+        * Protect access to I/O registers from concurrent modesetting
+        * by acquiring the I/O-register lock.
+        */
+       mutex_lock(&mdev->rmmio_lock);
+
+       return 0;
+}
+
+static void mgag200_ddc_algo_bit_data_post_xfer(struct i2c_adapter *adapter)
+{
+       struct mgag200_ddc *ddc = i2c_get_adapdata(adapter);
+       struct mga_device *mdev = ddc->mdev;
+
+       mutex_unlock(&mdev->rmmio_lock);
+}
+
 static void mgag200_ddc_release(struct drm_device *dev, void *res)
 {
        struct mgag200_ddc *ddc = res;
@@ -133,6 +155,8 @@ struct i2c_adapter *mgag200_ddc_create(struct mga_device 
*mdev)
        bit->setscl = mgag200_ddc_algo_bit_data_setscl;
        bit->getsda = mgag200_ddc_algo_bit_data_getsda;
        bit->getscl = mgag200_ddc_algo_bit_data_getscl;
+       bit->pre_xfer = mgag200_ddc_algo_bit_data_pre_xfer;
+       bit->post_xfer = mgag200_ddc_algo_bit_data_post_xfer;
        bit->udelay = 10;
        bit->timeout = usecs_to_jiffies(2200);
 
diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c 
b/drivers/gpu/drm/mgag200/mgag200_mode.c
index cd1f48b2f9986..a04c2b550be02 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -743,23 +743,14 @@ void mgag200_crtc_atomic_destroy_state(struct drm_crtc 
*crtc, struct drm_crtc_st
 
 int mgag200_vga_connector_helper_get_modes(struct drm_connector *connector)
 {
-       struct mga_device *mdev = to_mga_device(connector->dev);
        const struct drm_edid *drm_edid;
        int count;
 
-       /*
-        * Protect access to I/O registers from concurrent modesetting
-        * by acquiring the I/O-register lock.
-        */
-       mutex_lock(&mdev->rmmio_lock);
-
        drm_edid = drm_edid_read(connector);
        drm_edid_connector_update(connector, drm_edid);
        count = drm_edid_connector_add_modes(connector);
        drm_edid_free(drm_edid);
 
-       mutex_unlock(&mdev->rmmio_lock);
-
        return count;
 }
 
-- 
2.45.0