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Date: Thu, 6 Apr 2023 04:52:07 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Jayesh Choudhary <j-choudhary@...com>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, krzysztof.kozlowski@...aro.org,
andrzej.hajda@...el.com, neil.armstrong@...aro.org,
rfoss@...nel.org, jonas@...boo.se, jernej.skrabec@...il.com,
airlied@...il.com, daniel@...ll.ch, robh+dt@...nel.org,
krzysztof.kozlowski+dt@...aro.org, sam@...nborg.org,
jani.nikula@...el.com, tzimmermann@...e.de, javierm@...hat.com,
ville.syrjala@...ux.intel.com, r-ravikumar@...com,
lyude@...hat.com, alexander.deucher@....com, sjakhade@...ence.com,
yamonkar@...ence.com, a-bhatia1@...com,
tomi.valkeinen@...asonboard.com
Subject: Re: [PATCH v2 2/2] drm: bridge: cdns-mhdp8546: Add support for no-hpd
Hi Jayesh,
Thank you for the patch.
On Wed, Apr 05, 2023 at 07:54:40PM +0530, Jayesh Choudhary wrote:
> From: Rahul T R <r-ravikumar@...com>
>
> In J721S2 EVMs DP0 hpd is not connected to correct
> hpd pin on SOC, to handle such cases, Add support for
> "no-hpd" property in the device tree node to disable
> hpd
s/hpd/hpd./
You can also reflow the commit message to 72 columns.
> Also change the log level for dpcd read failuers to
> debug, since framework retries 32 times for each read
s/read/read./
Doesn't this apply to writes as well ?
> Signed-off-by: Rahul T R <r-ravikumar@...com>
> Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
> ---
> .../drm/bridge/cadence/cdns-mhdp8546-core.c | 37 ++++++++++++++++---
> .../drm/bridge/cadence/cdns-mhdp8546-core.h | 1 +
> 2 files changed, 33 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> index f6822dfa3805..e177794b069d 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> @@ -54,6 +54,8 @@
> #include "cdns-mhdp8546-hdcp.h"
> #include "cdns-mhdp8546-j721e.h"
>
> +static int cdns_mhdp_update_link_status(struct cdns_mhdp_device *mhdp);
> +
> static int cdns_mhdp_mailbox_read(struct cdns_mhdp_device *mhdp)
> {
> int ret, empty;
> @@ -749,7 +751,7 @@ static int cdns_mhdp_fw_activate(const struct firmware *fw,
> * MHDP_HW_STOPPED happens only due to driver removal when
> * bridge should already be detached.
> */
> - if (mhdp->bridge_attached)
> + if (mhdp->bridge_attached && !mhdp->no_hpd)
> writel(~(u32)CDNS_APB_INT_MASK_SW_EVENT_INT,
> mhdp->regs + CDNS_APB_INT_MASK);
>
> @@ -845,7 +847,7 @@ static ssize_t cdns_mhdp_transfer(struct drm_dp_aux *aux,
> ret = cdns_mhdp_dpcd_read(mhdp, msg->address,
> msg->buffer, msg->size);
> if (ret) {
> - dev_err(mhdp->dev,
> + dev_dbg(mhdp->dev,
> "Failed to read DPCD addr %u\n",
> msg->address);
>
> @@ -1738,6 +1740,19 @@ static int cdns_mhdp_attach(struct drm_bridge *bridge,
>
> spin_unlock(&mhdp->start_lock);
>
> + if (mhdp->no_hpd) {
> + ret = wait_event_timeout(mhdp->fw_load_wq,
> + mhdp->hw_state == MHDP_HW_READY,
> + msecs_to_jiffies(100));
> + if (ret == 0) {
> + dev_err(mhdp->dev, "%s: Timeout waiting for fw loading\n",
> + __func__);
> + return -ETIMEDOUT;
> + }
> +
> + cdns_mhdp_update_link_status(mhdp);
> + return 0;
> + }
Missing blank line.
It's not clear to me while you need to wait for the state to change to
MHDP_HW_READY in the no_hpd case. This should be explained in the commit
message.
> /* Enable SW event interrupts */
> if (hw_ready)
> writel(~(u32)CDNS_APB_INT_MASK_SW_EVENT_INT,
> @@ -2256,7 +2271,16 @@ static int cdns_mhdp_update_link_status(struct cdns_mhdp_device *mhdp)
>
> mutex_lock(&mhdp->link_mutex);
>
> - mhdp->plugged = cdns_mhdp_detect_hpd(mhdp, &hpd_pulse);
> + if (mhdp->no_hpd) {
> + ret = drm_dp_dpcd_read_link_status(&mhdp->aux, status);
> + hpd_pulse = false;
> + if (ret < 0)
> + mhdp->plugged = false;
> + else
> + mhdp->plugged = true;
I think there's an issue with how the driver uses mhdp->plugged. In the
no_hpd case, you try to detect if a display is connected by reading the
link status at attach time, and then never update mhdp->plugged. This
means that if no display is connected at that point, functions like
cdns_mhdp_get_edid() will always fail, even if a display gets plugged
later. As the goal of this series is (as far as I understand) support
systems where the HPD signal could be connected to a SoC GPIO instead of
the bridge, I don't think this is good enough.
> + } else {
> + mhdp->plugged = cdns_mhdp_detect_hpd(mhdp, &hpd_pulse);
> + }
>
> if (!mhdp->plugged) {
> cdns_mhdp_link_down(mhdp);
> @@ -2451,6 +2475,8 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
> mhdp->aux.dev = dev;
> mhdp->aux.transfer = cdns_mhdp_transfer;
>
> + mhdp->no_hpd = of_property_read_bool(dev->of_node, "cdns,no-hpd");
> +
> mhdp->regs = devm_platform_ioremap_resource(pdev, 0);
> if (IS_ERR(mhdp->regs)) {
> dev_err(dev, "Failed to get memory resource\n");
> @@ -2526,8 +2552,9 @@ static int cdns_mhdp_probe(struct platform_device *pdev)
>
> mhdp->bridge.of_node = pdev->dev.of_node;
> mhdp->bridge.funcs = &cdns_mhdp_bridge_funcs;
> - mhdp->bridge.ops = DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID |
> - DRM_BRIDGE_OP_HPD;
> + mhdp->bridge.ops = DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID;
> + if (!mhdp->no_hpd)
> + mhdp->bridge.ops |= DRM_BRIDGE_OP_HPD;
> mhdp->bridge.type = DRM_MODE_CONNECTOR_DisplayPort;
> if (mhdp->info)
> mhdp->bridge.timings = mhdp->info->timings;
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h
> index bedddd510d17..6786ccb51387 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.h
> @@ -388,6 +388,7 @@ struct cdns_mhdp_device {
>
> bool link_up;
> bool plugged;
> + bool no_hpd;
>
> /*
> * "start_lock" protects the access to bridge_attached and
--
Regards,
Laurent Pinchart
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