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drm/bridge: Clear the DP_AUX_I2C_MOT bit passed in aux read command.

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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: adca62ec37 ("drm/bridge: anx7625: Support reading edid through aux channel")
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Xin Ji <xji@analogixsemi.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220217082224.1823916-1-hsinyi@chromium.org
This commit is contained in:
Hsin-Yi Wang 2022-02-17 16:22:25 +08:00 committed by Robert Foss
parent 7e302637ba
commit c0bbed9051
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GPG Key ID: 3EFD900F76D1D784
1 changed files with 2 additions and 0 deletions
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2
drivers/gpu/drm/bridge/analogix/anx7625.c
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@ -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 */