linux-kernel - [RFC PATCH 6/6] drm/bridge: parade-ps8640: Provide is_hpd_asserted() in struct drm_dp

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Message-Id: <20220408193536.RFC.6.Ie827321ce263be52fdb8c1276f6f8cc00d78029f@changeid>
Date:   Fri,  8 Apr 2022 19:36:28 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     dri-devel@...ts.freedesktop.org
Cc:     Robert Foss <robert.foss@...aro.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        Philip Chen <philipchen@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        linux-kernel@...r.kernel.org
Subject: [RFC PATCH 6/6] drm/bridge: parade-ps8640: Provide is_hpd_asserted() in struct drm_dp_aux

This implements the callback added by the patch ("drm/dp: Add
is_hpd_asserted() callback to struct drm_dp_aux").

With this change and all the two "DP AUX Endpoint" drivers changed to
use is_hpd_asserted(), we no longer need to have an long delay in the
AUX transfer function. It's up to the panel code to make sure that the
panel is powered now. If someone tried to call the aux transfer
function without making sure the panel is powered we'll just get a
normal transfer failure.

We'll still keep the "ensure" for HPD in the pre_enable()
function. Though it's probably not actually needed there, this driver
is used in the old mode (pre-DP AUX Endpoints) and it may be important
for those cases. If nothing else, it shouldn't cause any big problems.

Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

 drivers/gpu/drm/bridge/parade-ps8640.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
index 96e883985608..13c3cb5d34f3 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -190,6 +190,22 @@ static int ps8640_ensure_hpd(struct ps8640 *ps_bridge)
 	return ret;
 }
 
+static bool ps8640_is_hpd_asserted(struct drm_dp_aux *aux)
+{
+	struct ps8640 *ps_bridge = aux_to_ps8640(aux);
+	struct regmap *map = ps_bridge->regmap[PAGE2_TOP_CNTL];
+	struct device *dev = &ps_bridge->page[PAGE0_DP_CNTL]->dev;
+	unsigned int status = 0;
+
+	pm_runtime_get_sync(dev);
+	regmap_read(map, PAGE2_GPIO_H, &status);
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_autosuspend(dev);
+
+	/* GPIO9 signals HPD. See ps8640_ensure_hpd() */
+	return status & PS_GPIO9;
+}
+
 static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux *aux,
 				       struct drm_dp_aux_msg *msg)
 {
@@ -324,9 +340,7 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
 	int ret;
 
 	pm_runtime_get_sync(dev);
-	ret = ps8640_ensure_hpd(ps_bridge);
-	if (!ret)
-		ret = ps8640_aux_transfer_msg(aux, msg);
+	ret = ps8640_aux_transfer_msg(aux, msg);
 	pm_runtime_mark_last_busy(dev);
 	pm_runtime_put_autosuspend(dev);
 
@@ -679,6 +693,7 @@ static int ps8640_probe(struct i2c_client *client)
 	ps_bridge->aux.name = "parade-ps8640-aux";
 	ps_bridge->aux.dev = dev;
 	ps_bridge->aux.transfer = ps8640_aux_transfer;
+	ps_bridge->aux.is_hpd_asserted = ps8640_is_hpd_asserted;
 	drm_dp_aux_init(&ps_bridge->aux);
 
 	pm_runtime_enable(dev);
-- 
2.35.1.1178.g4f1659d476-goog