On Thu, Feb 17, 2022 at 04:22:25PM +0800, Hsin-Yi Wang wrote: > 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. Hi Hsin-Yi, thanks for the patch! Reviewed-by: Xin Ji <xji@xxxxxxxxxxxxxxxx> Thanks, Xin > > Fixes: adca62ec370c ("drm/bridge: anx7625: Support reading edid through aux channel") > Signed-off-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> > --- > v1->v2: Offline discussed with Xin Ji, it's better to clear the bit on > read commands only. > --- > drivers/gpu/drm/bridge/analogix/anx7625.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c > index 633618bafd75d3..2805e9bed2c2f4 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 */ > -- > 2.35.1.265.g69c8d7142f-goog