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From: Tian Yunhao <t123yh@outlook.com>
Cc: Tian Yunhao <t123yh@outlook.com>, David Airlie <airlied@linux.ie>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Maxime Ripard <mripard@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	Daniel Vetter <daniel@ffwll.ch>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Icenowy Zheng <icenowy@aosc.io>
Subject: [PATCH] drm/sun4i: tcon: Set min division of TCON0_DCLK to 1.
Date: Wed, 13 Nov 2019 13:27:25 +0000
Message-ID: <MN2PR08MB57905AD8A00C08DA219377C989760@MN2PR08MB5790.namprd08.prod.outlook.com> (raw)

The datasheet of V3s (and various other chips) wrote
that TCON0_DCLK_DIV can be >= 1 if only dclk is used,
and must >= 6 if dclk1 or dclk2 is used. As currently
neither dclk1 nor dclk2 is used (no writes to these
bits), let's set minimal division to 1.

If this minimal division is 6, some common dot clock
frequencies can't be produced (e.g. 30MHz will not be
possible and will fallback to 25MHz), which is
obviously not an expected behaviour.

Signed-off-by: Yunhao Tian <t123yh@outlook.com>
---
 drivers/gpu/drm/sun4i/sun4i_tcon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 04c721d0d3b9..b89439ed210d 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -488,7 +488,7 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
 
 	WARN_ON(!tcon->quirks->has_channel_0);
 
-	tcon->dclk_min_div = 6;
+	tcon->dclk_min_div = 1;
 	tcon->dclk_max_div = 127;
 	sun4i_tcon0_mode_set_common(tcon, mode);
 
-- 
2.23.0


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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-13 13:27 Tian Yunhao [this message]
2019-11-13 14:25 ` Maxime Ripard

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