Hi Matthias,

On 02/10/2019 21:44, Matthias Kaehlcke wrote:

The DDC/CI protocol involves sending a multi-byte request to the display via I2C, which is typically followed by a multi-byte response. The internal I2C controller only allows single byte reads/writes or reads of 8 sequential bytes, hence DDC/CI is not supported when the internal I2C controller is used. The I2C transfers complete without errors, however the data in the response is garbage. Abort transfers to/from slave address 0x37 (DDC) with -EOPNOTSUPP, to make it evident that the communication is failing.

Signed-off-by: Matthias Kaehlcke mka@chromium.org Reviewed-by: Douglas Anderson dianders@chromium.org Reviewed-by: Sean Paul sean@poorly.run Acked-by: Neil Armstrong narmstrong@baylibre.com

---

Sorry for the delay with sending v2, I completely forgot about this patch ...

Changes in v2:

• updated comment with 'TOFIX' entry as requested by Neil
• added Neil's 'Acked-by' tag

drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 10 ++++++++++ 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c index 52d220a70362..ac24bceaf415 100644 --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c @@ -41,6 +41,7 @@

#include <media/cec-notifier.h>

+#define DDC_CI_ADDR 0x37 #define DDC_SEGMENT_ADDR 0x30

#define HDMI_EDID_LEN 512 @@ -439,6 +440,15 @@ static int dw_hdmi_i2c_xfer(struct i2c_adapter *adap, u8 addr = msgs[0].addr; int i, ret = 0;

• if (addr == DDC_CI_ADDR)

• /*
  

•  * The internal I2C controller does not support the multi-byte
  

•  * read and write operations needed for DDC/CI.
  

•  * TOFIX: Blacklist the DDC/CI address until we filter out
  

•  * unsupported I2C operations.
  

•  */
  

• return -EOPNOTSUPP;
  

• dev_dbg(hdmi->dev, "xfer: num: %d, addr: %#x\n", num, addr);

  for (i = 0; i < num; i++) {

Applying to drm-misc-next

Thanks ! Neil