From: CK Hu <ck.hu@mediatek.com>
To: Rex-BC Chen <rex-bc.chen@mediatek.com>,
"chunkuang.hu@kernel.org" <chunkuang.hu@kernel.org>,
"p.zabel@pengutronix.de" <p.zabel@pengutronix.de>,
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Cc: "msp@baylibre.com" <msp@baylibre.com>,
"granquet@baylibre.com" <granquet@baylibre.com>,
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Project_Global_Chrome_Upstream_Group
<Project_Global_Chrome_Upstream_Group@mediatek.com>
Subject: Re: [PATCH v14 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver
Date: Thu, 21 Jul 2022 14:24:58 +0800 [thread overview]
Message-ID: <4e543dc3a183af3966aa6f2f28b0afb9d95cbac2.camel@mediatek.com> (raw)
In-Reply-To: <7b1a555ab62aec8c3f5717b8827c81a2076bf569.camel@mediatek.com>
Hi, Rex:
On Thu, 2022-07-21 at 10:38 +0800, Rex-BC Chen wrote:
> On Fri, 2022-07-15 at 16:51 +0800, CK Hu wrote:
> > Hi, Bo-Chen:
> >
> > On Tue, 2022-07-12 at 19:12 +0800, Bo-Chen Chen wrote:
> > > From: Markus Schneider-Pargmann <msp@baylibre.com>
> > >
> > > This patch adds a embedded displayport driver for the MediaTek
> > > mt8195
> > > SoC.
> > >
> > > It supports the MT8195, the embedded DisplayPort units. It offers
> > > DisplayPort 1.4 with up to 4 lanes.
> > >
> > > The driver creates a child device for the phy. The child device
> > > will
> > > never exist without the parent being active. As they are sharing
> > > a
> > > register range, the parent passes a regmap pointer to the child
> > > so
> > > that
> > > both can work with the same register range. The phy driver sets
> > > device
> > > data that is read by the parent to get the phy device that can be
> > > used
> > > to control the phy properties.
> > >
> > > This driver is based on an initial version by
> > > Jitao shi <jitao.shi@mediatek.com>
> > >
> > > Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> > > Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
> > > Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
> > > ---
> >
> > [snip]
> >
> > > +static void mtk_dp_hpd_sink_event(struct mtk_dp *mtk_dp)
> > > +{
> > > + ssize_t ret;
> > > + u8 sink_count;
> > > + u8 link_status[DP_LINK_STATUS_SIZE] = {};
> > > + u32 sink_count_reg = DP_SINK_COUNT_ESI;
> > > + u32 link_status_reg = DP_LANE0_1_STATUS;
> > > +
> > > + ret = drm_dp_dpcd_readb(&mtk_dp->aux, sink_count_reg,
> > > &sink_count);
> >
> > According to your last reply, if drm_dp_dpcd_readb() fail, we could
> > skip below statement. So this just for error checking? If so, the
> > next
> > drm_dp_dpcd_read() would also do the error checking, so the
> > checking
> > here is redundant.
> >
> > Regards,
> > CK
> >
>
> Hello CK,
>
> sorry, I don't get your point.
> We use "drm_dp_dpcd_readb(&mtk_dp->aux, sink_count_reg, &sink_count)"
> to get sink count and use "drm_dp_dpcd_read(&mtk_dp->aux,
> link_status_reg, link_status, sizeof(link_status));" to get link
> status.
>
> If we don't get any sink count, we don't need to check the link
> status.
> Therefore, we just return if we are failed to get sink count.
I assume that when error happen, both read sink_count and read
link_status would fail, so you could directly read link_status. Do you
think that when error happen, only read sink_count would fail and read
link_status would success? It it is the later case, we should keep the
checking of sink_count.
Regards,
CK
>
> BRs,
> Bo-Chen
>
> > > + if (ret < 1) {
> > > + drm_err(mtk_dp->drm_dev, "Read sink count failed\n");
> > > + return;
> > > + }
> > > +
> > > + drm_dbg(mtk_dp->drm_dev,
> > > + "read sink count from dpcd: %d\n", sink_count);
> > > +
> > > + ret = drm_dp_dpcd_read(&mtk_dp->aux, link_status_reg,
> > > link_status,
> > > + sizeof(link_status));
> > > + if (!ret) {
> > > + drm_err(mtk_dp->drm_dev, "Read link status failed\n");
> > > + return;
> > > + }
> > > +
> > > + if (!drm_dp_channel_eq_ok(link_status, mtk_dp-
> > > > train_info.lane_count)) {
> > >
> > > + drm_err(mtk_dp->drm_dev, "Channel EQ failed\n");
> > > + return;
> > > + }
> > > +
> > > + if (link_status[1] & DP_REMOTE_CONTROL_COMMAND_PENDING)
> > > + drm_dp_dpcd_writeb(&mtk_dp->aux,
> > > DP_DEVICE_SERVICE_IRQ_VECTOR,
> > > + DP_REMOTE_CONTROL_COMMAND_PENDING);
> > > +}
> > > +
> >
> >
>
>
next prev parent reply other threads:[~2022-07-21 6:25 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-12 11:12 [PATCH v14 00/10] drm/mediatek: Add MT8195 DisplayPort driver Bo-Chen Chen
2022-07-12 11:12 ` [PATCH v14 01/10] dt-bindings: mediatek,dp: Add Display Port binding Bo-Chen Chen
2022-07-13 7:56 ` CK Hu
2022-07-26 6:18 ` Rex-BC Chen
2022-07-26 8:46 ` CK Hu
2022-07-18 20:21 ` Rob Herring
2022-07-12 11:12 ` [PATCH v14 02/10] drm/edid: Convert cea_sad helper struct to kernelDoc Bo-Chen Chen
2022-07-12 11:12 ` [PATCH v14 03/10] drm/edid: Add cea_sad helpers for freq/length Bo-Chen Chen
2022-07-14 11:12 ` AngeloGioacchino Del Regno
2022-07-14 11:19 ` Rex-BC Chen
2022-07-12 11:12 ` [PATCH v14 04/10] video/hdmi: Add audio_infoframe packing for DP Bo-Chen Chen
2022-07-14 11:26 ` AngeloGioacchino Del Regno
2022-07-12 11:12 ` [PATCH v14 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver Bo-Chen Chen
2022-07-13 8:03 ` CK Hu
2022-07-13 8:10 ` CK Hu
2022-07-14 8:24 ` Rex-BC Chen
2022-07-14 10:21 ` CK Hu
2022-07-13 8:22 ` CK Hu
2022-07-13 8:30 ` CK Hu
2022-07-13 9:12 ` CK Hu
2022-07-13 9:31 ` CK Hu
2022-07-14 8:52 ` Rex-BC Chen
2022-07-13 9:33 ` CK Hu
2022-07-14 8:57 ` Rex-BC Chen
2022-07-13 9:45 ` CK Hu
2022-07-14 6:51 ` CK Hu
2022-07-14 9:09 ` Rex-BC Chen
2022-07-14 10:34 ` CK Hu
2022-07-14 7:06 ` CK Hu
2022-07-15 8:51 ` CK Hu
2022-07-21 2:38 ` Rex-BC Chen
2022-07-21 6:24 ` CK Hu [this message]
2022-07-15 9:13 ` CK Hu
2022-07-15 9:14 ` CK Hu
2022-07-15 9:37 ` CK Hu
2022-07-15 18:01 ` kernel test robot
2022-07-25 9:16 ` CK Hu
2022-07-26 6:42 ` Rex-BC Chen
2022-07-26 9:34 ` CK Hu
2022-07-26 10:06 ` Rex-BC Chen
2022-07-25 9:23 ` CK Hu
2022-07-26 3:30 ` Rex-BC Chen
2022-07-26 8:37 ` CK Hu
2022-07-12 11:12 ` [PATCH v14 06/10] drm/mediatek: Add MT8195 External DisplayPort support Bo-Chen Chen
2022-07-25 9:51 ` CK Hu
2022-07-12 11:12 ` [PATCH v14 07/10] drm/mediatek: add hpd debounce Bo-Chen Chen
2022-07-12 11:12 ` [PATCH v14 08/10] drm/mediatek: set monitor to DP_SET_POWER_D3 to avoid garbage Bo-Chen Chen
2022-07-12 11:12 ` [PATCH v14 09/10] drm/mediatek: DP audio support for MT8195 Bo-Chen Chen
2022-07-14 11:43 ` AngeloGioacchino Del Regno
2022-07-12 11:12 ` [PATCH v14 10/10] drm/mediatek: Use cached audio config when changing resolution Bo-Chen Chen
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