diff options
| author | Matthias Kaehlcke <mka@chromium.org> | 2019-10-02 12:44:06 -0700 |
|---|---|---|
| committer | Neil Armstrong <narmstrong@baylibre.com> | 2019-10-07 14:27:48 +0200 |
| commit | bee447e224b2645911c5d06e35dc90d8433fcef6 (patch) | |
| tree | 892a6b7226dd636cf637507b637d2e50f8bc938e /drivers/gpu/drm/bridge | |
| parent | 4340ec45e895c4bd25e9bcdb3b88cd192fd9512c (diff) | |
drm/bridge: dw-hdmi: Refuse DDC/CI transfers on the internal I2C controller
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>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191002124354.v2.1.I709dfec496f5f0b44a7b61dcd4937924da8d8382@changeid
Diffstat (limited to 'drivers/gpu/drm/bridge')
| -rw-r--r-- | drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c index d77fb8af61b8..a15fbf71b9d7 100644 --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c @@ -37,6 +37,7 @@ #include "dw-hdmi-cec.h" #include "dw-hdmi.h" +#define DDC_CI_ADDR 0x37 #define DDC_SEGMENT_ADDR 0x30 #define HDMI_EDID_LEN 512 @@ -399,6 +400,15 @@ 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++) { |