| Message ID | 20200103055001.10287-1-Wayne.Lin@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] drm/dp_mst: correct the shifting in DP_REMOTE_I2C_READ | expand |
On 2020-01-03 12:50 a.m., 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. > Thanks for elaborating on the potential consequences of this bug. Harry > [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@amd.com> > Signed-off-by: Wayne Lin <Wayne.Lin@amd.com> > Cc: stable@vger.kernel.org > --- > 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++; > } >
Reviewed-by: Lyude Paul <lyude@redhat.com> Thanks for all of the contributions you've made as of late! I will go ahead and push this into drm-misc-fixes 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@amd.com> > Signed-off-by: Wayne Lin <Wayne.Lin@amd.com> > Cc: stable@vger.kernel.org > --- > 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++; > }
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@amd.com>
> Signed-off-by: Wayne Lin <Wayne.Lin@amd.com>
> Cc: stable@vger.kernel.org
> ---
> 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++;
> }
[AMD Public Use] > -----Original Message----- > From: Lyude Paul <lyude@redhat.com> > Sent: Saturday, January 4, 2020 6:02 AM > To: Lin, Wayne <Wayne.Lin@amd.com>; dri-devel@lists.freedesktop.org; > amd-gfx@lists.freedesktop.org > Cc: Kazlauskas, Nicholas <Nicholas.Kazlauskas@amd.com>; Wentland, Harry > <Harry.Wentland@amd.com>; Zuo, Jerry <Jerry.Zuo@amd.com>; > stable@vger.kernel.org > Subject: Re: [PATCH v2] drm/dp_mst: correct the shifting in > DP_REMOTE_I2C_READ > > 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 > Really appreciate for your time! I will have a look on this. Thanks a lot. > 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://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2F > > > patchwork.kernel.org%2Fpatch%2F11312667%2F&data=02%7C01%7Cw > ayne.li > > > n%40amd.com%7Ce4299c1721bd4bcb486708d790989148%7C3dd8961fe4884e > 608e11a > > > 82d994e183d%7C0%7C0%7C637136857271065549&sdata=eoxiRojffBepY > YoQbjp > > j8b6R%2BkwaOQWBoU%2Fu8lY5gIQ%3D&reserved=0) > > * 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@amd.com> > > Signed-off-by: Wayne Lin <Wayne.Lin@amd.com> > > Cc: stable@vger.kernel.org > > --- > > 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 -- Best Regards, Wayne Lin
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++; }