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From:   Roman Beranek <me@crly.cz>
To:     Maxime Ripard <mripard@kernel.org>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>, Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc:     Frank Oltmanns <frank@oltmanns.dev>,
        Icenowy Zheng <icenowy@aosc.io>, Ondrej Jirman <megi@xff.cz>,
        devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev,
        linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v4 1/4] clk: sunxi-ng: a64: force select PLL_MIPI in TCON0 mux
Date:   Fri,  5 May 2023 07:21:07 +0200
Message-Id: <20230505052110.67514-2-me@crly.cz>
In-Reply-To: <20230505052110.67514-1-me@crly.cz>
References: <20230505052110.67514-1-me@crly.cz>
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TCON0's source clock can be fed from either PLL_MIPI, or PLL_VIDEO0(2X),
however MIPI DSI output only seems to work when PLL_MIPI is selected and
thus the choice must be hardcoded in.

Currently, this driver can't propagate rate change from N-K-M clocks
(such as PLL_MIPI) upwards. This prevents PLL_VIDEO0 from participating
in setting of the TCON0 data clock rate, limiting the precision with
which a target pixel clock can be matched.

For outputs with fixed TCON0 divider, that is DSI and LVDS, the dotclock
can deviate up to 8% off target.

Signed-off-by: Roman Beranek <me@crly.cz>
---
 drivers/clk/sunxi-ng/ccu-sun50i-a64.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
index 41519185600a..eb36f8f77d55 100644
--- a/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
+++ b/drivers/clk/sunxi-ng/ccu-sun50i-a64.c
@@ -528,11 +528,18 @@ static SUNXI_CCU_M_WITH_MUX_GATE(de_clk, "de", de_parents,
 				 0x104, 0, 4, 24, 3, BIT(31),
 				 CLK_SET_RATE_PARENT);
 
+/*
+ * DSI output seems to work only when PLL_MIPI selected. Set it and prevent
+ * the mux from reparenting.
+ */
+#define SUN50I_A64_TCON0_CLK_REG	0x118
+
 static const char * const tcon0_parents[] = { "pll-mipi", "pll-video0-2x" };
 static const u8 tcon0_table[] = { 0, 2, };
 static SUNXI_CCU_MUX_TABLE_WITH_GATE(tcon0_clk, "tcon0", tcon0_parents,
 				     tcon0_table, 0x118, 24, 3, BIT(31),
-				     CLK_SET_RATE_PARENT);
+				     CLK_SET_RATE_PARENT |
+				     CLK_SET_RATE_NO_REPARENT);
 
 static const char * const tcon1_parents[] = { "pll-video0", "pll-video1" };
 static const u8 tcon1_table[] = { 0, 2, };
@@ -953,6 +960,11 @@ static int sun50i_a64_ccu_probe(struct platform_device *pdev)
 
 	writel(0x515, reg + SUN50I_A64_PLL_MIPI_REG);
 
+	/* Set PLL MIPI as parent for TCON0 */
+	val = readl(reg + SUN50I_A64_TCON0_CLK_REG);
+	val &= ~GENMASK(26, 24);
+	writel(val | (0 << 24), reg + SUN50I_A64_TCON0_CLK_REG);
+
 	ret = devm_sunxi_ccu_probe(&pdev->dev, reg, &sun50i_a64_ccu_desc);
 	if (ret)
 		return ret;
-- 
2.32.0 (Apple Git-132)