linux-kernel - [PATCH] drm/sun4i: Workaround TCON TOP conflict between DE0 and DE1

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Message-Id: <20241108-tcon_fix-v1-1-616218cc0d5f@jookia.org>
Date: Fri, 08 Nov 2024 12:40:16 +1100
From: John Watts <contact@...kia.org>
To: Maxime Ripard <mripard@...nel.org>, Chen-Yu Tsai <wens@...e.org>, 
 Jernej Skrabec <jernej.skrabec@...il.com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
 Daniel Vetter <daniel@...ll.ch>, Samuel Holland <samuel@...lland.org>
Cc: dri-devel@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org, 
 linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org, 
 John Watts <contact@...kia.org>
Subject: [PATCH] drm/sun4i: Workaround TCON TOP conflict between DE0 and
 DE1

On the D1 and T113 the TCON TOP cannot handle setting both DEs to a
single output, even if the outputs are disabled. As a workaround assign
DE1 to TVE0 by default.

A full fix for this would include logic that makes sure both DEs never
share the same output.

Signed-off-by: John Watts <contact@...kia.org>
---
 drivers/gpu/drm/sun4i/sun8i_tcon_top.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
index a1ca3916f42bcc63b9ac7643e788d962ef360ca8..543311ffb1509face3fbfd069ded10933f254b9d 100644
--- a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
+++ b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
@@ -179,7 +179,7 @@ static int sun8i_tcon_top_bind(struct device *dev, struct device *master,
 	 * At least on H6, some registers have some bits set by default
 	 * which may cause issues. Clear them here.
 	 */
-	writel(0, regs + TCON_TOP_PORT_SEL_REG);
+	writel(0x20, regs + TCON_TOP_PORT_SEL_REG);
 	writel(0, regs + TCON_TOP_GATE_SRC_REG);
 
 	/*

---
base-commit: 98f7e32f20d28ec452afb208f9cffc08448a2652
change-id: 20241108-tcon_fix-f0585ac9bae0

Best regards,
-- 
John Watts <contact@...kia.org>