From: "Lin, Wayne" <Wayne.Lin@amd.com> To: "Wentland, Harry" <Harry.Wentland@amd.com>, "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>, "amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org> Cc: "Zuo, Jerry" <Jerry.Zuo@amd.com>, "Kazlauskas, Nicholas" <Nicholas.Kazlauskas@amd.com> Subject: Re: [PATCH] drm/dp_mst: correct the shifting in DP_REMOTE_I2C_READ Date: Tue, 31 Dec 2019 04:00:01 +0000 [thread overview] Message-ID: <DM6PR12MB413708FA6DB61C4CCE1ADFECFC260@DM6PR12MB4137.namprd12.prod.outlook.com> (raw) In-Reply-To: <084e73fe-0f8c-a9da-3b20-0dc6804e8602@amd.com> [AMD Official Use Only - Internal Distribution Only] > ________________________________________ > From: Wentland, Harry <Harry.Wentland@amd.com> > Sent: Monday, December 30, 2019 23:26 > To: Lin, Wayne; dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org > Cc: lyude@redhat.com; Zuo, Jerry; Kazlauskas, Nicholas; Wentland, Harry > Subject: Re: [PATCH] drm/dp_mst: correct the shifting in DP_REMOTE_I2C_READ > > On 2019-12-30 2:05 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. > > > > [How] > > Correct the shifting value of NO_STOP_BIT for DP_REMOTE_I2C_READ case in > > drm_dp_encode_sideband_req(). > > > > Signed-off-by: Wayne Lin <Wayne.Lin@amd.com> > > Good catch. Looks like this has been there since the beginning of MST in > the kernel. How did you find this? Did this cause bad EDID reads or some > other problem? If so the commit message should probably mention it. > > Harry Thanks for your time. I found this while I was trying to debug MST issues by using AUX monitor. So far, I don't observe problems that relate to this under my test cases and environment. However, this bit might affect the I2C signal generated by I2C master, I will mention more in the commit message. Thanks. > > > --- > > 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 1d1bfa49ca2b..0557e225ff67 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++; > > } > > -- Wayne Lin _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
WARNING: multiple messages have this Message-ID (diff)
From: "Lin, Wayne" <Wayne.Lin@amd.com> To: "Wentland, Harry" <Harry.Wentland@amd.com>, "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>, "amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org> Cc: "Zuo, Jerry" <Jerry.Zuo@amd.com>, "Kazlauskas, Nicholas" <Nicholas.Kazlauskas@amd.com> Subject: Re: [PATCH] drm/dp_mst: correct the shifting in DP_REMOTE_I2C_READ Date: Tue, 31 Dec 2019 04:00:01 +0000 [thread overview] Message-ID: <DM6PR12MB413708FA6DB61C4CCE1ADFECFC260@DM6PR12MB4137.namprd12.prod.outlook.com> (raw) In-Reply-To: <084e73fe-0f8c-a9da-3b20-0dc6804e8602@amd.com> [AMD Official Use Only - Internal Distribution Only] > ________________________________________ > From: Wentland, Harry <Harry.Wentland@amd.com> > Sent: Monday, December 30, 2019 23:26 > To: Lin, Wayne; dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org > Cc: lyude@redhat.com; Zuo, Jerry; Kazlauskas, Nicholas; Wentland, Harry > Subject: Re: [PATCH] drm/dp_mst: correct the shifting in DP_REMOTE_I2C_READ > > On 2019-12-30 2:05 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. > > > > [How] > > Correct the shifting value of NO_STOP_BIT for DP_REMOTE_I2C_READ case in > > drm_dp_encode_sideband_req(). > > > > Signed-off-by: Wayne Lin <Wayne.Lin@amd.com> > > Good catch. Looks like this has been there since the beginning of MST in > the kernel. How did you find this? Did this cause bad EDID reads or some > other problem? If so the commit message should probably mention it. > > Harry Thanks for your time. I found this while I was trying to debug MST issues by using AUX monitor. So far, I don't observe problems that relate to this under my test cases and environment. However, this bit might affect the I2C signal generated by I2C master, I will mention more in the commit message. Thanks. > > > --- > > 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 1d1bfa49ca2b..0557e225ff67 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++; > > } > > -- Wayne Lin _______________________________________________ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
next prev parent reply other threads:[~2019-12-31 4:00 UTC|newest] Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-12-30 7:05 [PATCH] drm/dp_mst: correct the shifting in DP_REMOTE_I2C_READ Wayne Lin 2019-12-30 7:05 ` Wayne Lin 2019-12-30 11:15 ` Jani Nikula 2019-12-30 11:15 ` Jani Nikula 2019-12-31 3:30 ` Lin, Wayne 2019-12-31 3:30 ` Lin, Wayne 2020-01-07 18:57 ` Ville Syrjälä 2020-01-07 18:57 ` Ville Syrjälä 2020-01-08 2:34 ` Lin, Wayne 2020-01-08 2:34 ` Lin, Wayne 2019-12-30 15:26 ` Harry Wentland 2019-12-30 15:26 ` Harry Wentland 2019-12-31 4:00 ` Lin, Wayne [this message] 2019-12-31 4:00 ` Lin, Wayne 2019-12-31 14:40 ` Harry Wentland 2019-12-31 14:40 ` Harry Wentland
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