linux-kernel - [PATCH] drm: bridge: adv7511: get edid in hpd

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Message-Id: <20231014-adv7511-cec-edid-v1-1-a58ceae0b57e@bang-olufsen.dk>
Date:   Sat, 14 Oct 2023 21:43:01 +0200
From:   Alvin Šipraga <alvin@...s.dk>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Alvin Šipraga <alsi@...g-olufsen.dk>
Subject: [PATCH] drm: bridge: adv7511: get edid in hpd_work to update CEC
 phys address

From: Alvin Šipraga <alsi@...g-olufsen.dk>

The adv7511 driver is solely responsible for setting the physical
address of its CEC adapter. To do this, it must read the EDID. However,
EDID is only read when either the drm_bridge_funcs :: get_edid or
drm_connector_helper_funcs :: get_modes ops are called. Without loss of
generality, it cannot be assumed that these ops are called when a sink
gets attached. Therefore there exist scenarios in which the CEC physical
address will be invalid (f.f.f.f), rendering the CEC adapter inoperable.

Address this problem by always fetching the EDID in the HPD work when we
detect a connection. The CEC physical address is set in the process.

Signed-off-by: Alvin Šipraga <alsi@...g-olufsen.dk>
---
Pardon the insertion of the ugly adv7511_get_edid() prototype, but I did
not want to clobber git history by rearranging a bunch of functions. If
this is the preferred approach I will happily re-spin the patch.
---
 drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
index 2611afd2c1c1..3d32c109963c 100644
--- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
+++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
@@ -424,6 +424,9 @@ static bool adv7511_hpd(struct adv7511 *adv7511)
 	return false;
 }
 
+static struct edid *adv7511_get_edid(struct adv7511 *adv7511,
+				     struct drm_connector *connector);
+
 static void adv7511_hpd_work(struct work_struct *work)
 {
 	struct adv7511 *adv7511 = container_of(work, struct adv7511, hpd_work);
@@ -457,6 +460,9 @@ static void adv7511_hpd_work(struct work_struct *work)
 		if (adv7511->connector.dev) {
 			if (status == connector_status_disconnected)
 				cec_phys_addr_invalidate(adv7511->cec_adap);
+			else
+				adv7511_get_edid(adv7511, &adv7511->connector);
+
 			drm_kms_helper_hotplug_event(adv7511->connector.dev);
 		} else {
 			drm_bridge_hpd_notify(&adv7511->bridge, status);

---
base-commit: 4366faf43308bd91c59a20c43a9f853a9c3bb6e4
change-id: 20231014-adv7511-cec-edid-ff75bd3ac929