From: Xin Ji <xji@analogixsemi.com>
To: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Robert Foss <robert.foss@linaro.org>,
Neil Armstrong <narmstrong@baylibre.com>,
Jernej Skrabec <jernej.skrabec@gmail.com>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
Daniel Vetter <daniel@ffwll.ch>,
Andrzej Hajda <andrzej.hajda@intel.com>
Subject: Re: [PATCH v2] drm/bridge: Clear the DP_AUX_I2C_MOT bit passed in aux read command.
Date: Thu, 17 Feb 2022 16:31:19 +0800 [thread overview]
Message-ID: <20220217083119.GA3781632@anxtwsw-Precision-3640-Tower> (raw)
In-Reply-To: <20220217082224.1823916-1-hsinyi@chromium.org>
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@analogixsemi.com>
Thanks,
Xin
>
> Fixes: adca62ec370c ("drm/bridge: anx7625: Support reading edid through aux channel")
> Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
> ---
> 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
next prev parent reply other threads:[~2022-02-17 8:31 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-17 8:22 [PATCH v2] drm/bridge: Clear the DP_AUX_I2C_MOT bit passed in aux read command Hsin-Yi Wang
2022-02-17 8:31 ` Xin Ji [this message]
2022-03-01 8:57 ` Hsin-Yi Wang
2022-03-01 13:03 ` Robert Foss
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