linux-kernel - [PATCH v1 4/5] drm/bridge: tc358768: Disable non-continuous clock mode

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Date:   Sun,  3 Oct 2021 02:34:46 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maxim Schwalm <maxim.schwalm@...il.com>,
        Andreas Westman Dorcsak <hedmoo@...oo.com>,
        Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v1 4/5] drm/bridge: tc358768: Disable non-continuous clock mode

Non-continuous clock mode doesn't work because driver doesn't support it
properly. The bridge driver programs wrong bitfields that are required by
the non-continuous mode (BTACNTRL1 register bitfields are swapped in the
code), but fixing them doesn't help.

Display panel of ASUS Transformer TF700T tablet supports non-continuous
mode and display doesn't work at all using that mode. There are no
device-trees that are actively using this DSI bridge in upstream yet,
so clearly the broken mode wasn't ever tested properly. It's a bit too
difficult to get LP mode working, hence let's disable the offending mode
for now and fall back to continuous mode.

Tested-by: Andreas Westman Dorcsak <hedmoo@...oo.com> # Asus TF700T
Tested-by: Maxim Schwalm <maxim.schwalm@...il.com> #TF700T
Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/gpu/drm/bridge/tc358768.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c
index 5b3f8723bd3d..cfceba5ef3b8 100644
--- a/drivers/gpu/drm/bridge/tc358768.c
+++ b/drivers/gpu/drm/bridge/tc358768.c
@@ -631,6 +631,7 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
 {
 	struct tc358768_priv *priv = bridge_to_tc358768(bridge);
 	struct mipi_dsi_device *dsi_dev = priv->output.dev;
+	unsigned long mode_flags = dsi_dev->mode_flags;
 	u32 val, val2, lptxcnt, hact, data_type;
 	const struct drm_display_mode *mode;
 	u32 dsibclk_nsk, dsiclk_nsk, ui_nsk, phy_delay_nsk;
@@ -638,6 +639,11 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
 	const u32 internal_delay = 40;
 	int ret, i;
 
+	if (mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS) {
+		dev_warn_once(priv->dev, "Non-continuous mode unimplemented, falling back to continuous\n");
+		mode_flags &= ~MIPI_DSI_CLOCK_NON_CONTINUOUS;
+	}
+
 	tc358768_hw_enable(priv);
 
 	ret = tc358768_sw_reset(priv);
@@ -776,7 +782,7 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
 		val |= BIT(i + 1);
 	tc358768_write(priv, TC358768_HSTXVREGEN, val);
 
-	if (!(dsi_dev->mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS))
+	if (!(mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS))
 		tc358768_write(priv, TC358768_TXOPTIONCNTRL, 0x1);
 
 	/* TXTAGOCNT[26:16] RXTASURECNT[10:0] */
@@ -864,7 +870,7 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
 	if (!(dsi_dev->mode_flags & MIPI_DSI_MODE_LPM))
 		val |= TC358768_DSI_CONTROL_TXMD;
 
-	if (!(dsi_dev->mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS))
+	if (!(mode_flags & MIPI_DSI_CLOCK_NON_CONTINUOUS))
 		val |= TC358768_DSI_CONTROL_HSCKMD;
 
 	if (dsi_dev->mode_flags & MIPI_DSI_MODE_NO_EOT_PACKET)
-- 
2.32.0