From: Hsin-Yi Wang Date: Thu, 17 Feb 2022 08:22:25 +0000 (+0800) Subject: drm/bridge: Clear the DP_AUX_I2C_MOT bit passed in aux read command. X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c0bbed9051b6eb293be6128d060bb49e999ef7d4;p=linux.git drm/bridge: Clear the DP_AUX_I2C_MOT bit passed in aux read command. If the previous transfer didn't end with a command without DP_AUX_I2C_MOT, the next read trasnfer will miss the first byte. But if the command in previous transfer is requested with length 0, it's a no-op to anx7625 since it can't process this command. anx7625 requires the last command to be read command with length > 0. It's observed that if we clear the DP_AUX_I2C_MOT in read transfer, we can still get correct data. Clear the read commands with DP_AUX_I2C_MOT bit to fix this issue. Fixes: adca62ec370c ("drm/bridge: anx7625: Support reading edid through aux channel") Signed-off-by: Hsin-Yi Wang Reviewed-by: Xin Ji Signed-off-by: Robert Foss Link: https://patchwork.freedesktop.org/patch/msgid/20220217082224.1823916-1-hsinyi@chromium.org --- diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c index 9aab879a88513..31ecf5626f1d9 100644 --- a/drivers/gpu/drm/bridge/analogix/anx7625.c +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c @@ -253,6 +253,8 @@ static int anx7625_aux_trans(struct anx7625_data *ctx, u8 op, u32 address, addrm = (address >> 8) & 0xFF; addrh = (address >> 16) & 0xFF; + if (!is_write) + op &= ~DP_AUX_I2C_MOT; cmd = DPCD_CMD(len, op); /* Set command and length */