Oh! Just a friendly tip, I fixed this before pushing your patch:
➜ drm-maint git:(drm-misc-fixes) dim push
dim: 0b1d54cedbb4 ("drm/dp_mst: correct the shifting in DP_REMOTE_I2C_READ"): Fixes: SHA1 needs at least 12 digits:
dim: ad7f8a1f9ce (drm/helper: add Displayport multi-stream helper (v0.6))
dim: ERROR: issues in commits detected, aborting
For the future, we have a set of DRM maintainer tools (they're quite useful
for people who aren't maintainers though!) that you can use to make sure your
patch is formatted correctly ahead of time:
https://drm.pages.freedesktop.org/maintainer-tools/dim.html
Particularly useful commands:
* dim sparse # Checks for trivial code issues, like set but unused variables
* dim checkpatch # Checks for code style issues
* dim fixes $COMMIT_ID # Adds an appropriately formatted Fixes: tag
* dim cite $COMMIT_ID # Adds an appropriately formatted Reference: tag
On Fri, 2020-01-03 at 13:50 +0800, Wayne Lin wrote:
> [Why]
> According to DP spec, it should shift left 4 digits for NO_STOP_BIT
> in REMOTE_I2C_READ message. Not 5 digits.
>
> In current code, NO_STOP_BIT is always set to zero which means I2C
> master is always generating a I2C stop at the end of each I2C write
> transaction while handling REMOTE_I2C_READ sideband message. This issue
> might have the generated I2C signal not meeting the requirement. Take
> random read in I2C for instance, I2C master should generate a repeat
> start to start to read data after writing the read address. This issue
> will cause the I2C master to generate a stop-start rather than a
> re-start which is not expected in I2C random read.
>
> [How]
> Correct the shifting value of NO_STOP_BIT for DP_REMOTE_I2C_READ case in
> drm_dp_encode_sideband_req().
>
> Changes since v1:(https://patchwork.kernel.org/patch/11312667/)
> * Add more descriptions in commit and cc to stable
>
> Fixes: ad7f8a1f9ce (drm/helper: add Displayport multi-stream helper (v0.6))
> Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
> Signed-off-by: Wayne Lin <Wayne.Lin@xxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 1cf5f8b8bbb8..9d24c98bece1 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -393,7 +393,7 @@ drm_dp_encode_sideband_req(const struct
> drm_dp_sideband_msg_req_body *req,
> memcpy(&buf[idx], req-
> >u.i2c_read.transactions[i].bytes, req-
> >u.i2c_read.transactions[i].num_bytes);
> idx += req->u.i2c_read.transactions[i].num_bytes;
>
> - buf[idx] = (req-
> >u.i2c_read.transactions[i].no_stop_bit & 0x1) << 5;
> + buf[idx] = (req-
> >u.i2c_read.transactions[i].no_stop_bit & 0x1) << 4;
> buf[idx] |= (req-
> >u.i2c_read.transactions[i].i2c_transaction_delay & 0xf);
> idx++;
> }
--
Cheers,
Lyude Paul
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