linux-kernel - [PATCH 1/1] drm/sun4i: tcon: Fix setting PLL rate when using DSI

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Message-Id: <20230319160704.9858-2-frank@oltmanns.dev>
Date:   Sun, 19 Mar 2023 17:07:04 +0100
From:   Frank Oltmanns <frank@...manns.dev>
To:     jagan@...rulasolutions.com, michael@...rulasolutions.com,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        dri-devel@...ts.freedesktop.org (open list:DRM DRIVERS FOR ALLWINNER
        A10),
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM/Allwinner
        sunXi SoC support),
        linux-sunxi@...ts.linux.dev (open list:ARM/Allwinner sunXi SoC support),
        linux-kernel@...r.kernel.org (open list)
Cc:     Frank Oltmanns <frank@...manns.dev>
Subject: [PATCH 1/1] drm/sun4i: tcon: Fix setting PLL rate when using DSI

Set the required PLL rate by adjusting the dotclock rate when calling
clk_set_rate() when using DSI.

According to the Allwinners A64's BSP code, a TCON divider of 4 has to
be used and the PLL rate needs to be set to the following frequency when
using DSI:
    PLL rate = DCLK * bpp / lanes

After this change the common mode set function would only contain
setting the resolution. Therefore, dissolve the function and transfer
the functionality to the individual mode set functions.

Signed-off-by: Frank Oltmanns <frank@...manns.dev>
---
 drivers/gpu/drm/sun4i/sun4i_tcon.c | 46 ++++++++++++++++++++----------
 1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index 62b3538bd81f..02d52be42f06 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -323,18 +323,6 @@ static int sun4i_tcon_get_clk_delay(const struct drm_display_mode *mode,
 	return delay;
 }
 
-static void sun4i_tcon0_mode_set_common(struct sun4i_tcon *tcon,
-					const struct drm_display_mode *mode)
-{
-	/* Configure the dot clock */
-	clk_set_rate(tcon->dclk, mode->crtc_clock * 1000);
-
-	/* Set the resolution */
-	regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
-		     SUN4I_TCON0_BASIC0_X(mode->crtc_hdisplay) |
-		     SUN4I_TCON0_BASIC0_Y(mode->crtc_vdisplay));
-}
-
 static void sun4i_tcon0_mode_set_dithering(struct sun4i_tcon *tcon,
 					   const struct drm_connector *connector)
 {
@@ -399,10 +387,24 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon,
 	u32 block_space, start_delay;
 	u32 tcon_div;
 
+	/*
+	 * Configure the dot clock:
+	 * For DSI the PLL rate has to respect the bits per pixel and
+	 * number of lanes.
+	 *
+	 * According to the BSP code:
+	 * TCON divider = 4
+	 * PLL rate = DCLK * bpp / lanes
+	 */
 	tcon->dclk_min_div = SUN6I_DSI_TCON_DIV;
 	tcon->dclk_max_div = SUN6I_DSI_TCON_DIV;
+	clk_set_rate(tcon->dclk, mode->crtc_clock * 1000
+				 * bpp / (lanes * SUN6I_DSI_TCON_DIV));
 
-	sun4i_tcon0_mode_set_common(tcon, mode);
+	/* Set the resolution */
+	regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
+		     SUN4I_TCON0_BASIC0_X(mode->crtc_hdisplay) |
+		     SUN4I_TCON0_BASIC0_Y(mode->crtc_vdisplay));
 
 	/* Set dithering if needed */
 	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
@@ -470,7 +472,14 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
 
 	tcon->dclk_min_div = 7;
 	tcon->dclk_max_div = 7;
-	sun4i_tcon0_mode_set_common(tcon, mode);
+
+	/* Configure the dot clock */
+	clk_set_rate(tcon->dclk, mode->crtc_clock * 1000);
+
+	/* Set the resolution */
+	regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
+		     SUN4I_TCON0_BASIC0_X(mode->crtc_hdisplay) |
+		     SUN4I_TCON0_BASIC0_Y(mode->crtc_vdisplay));
 
 	/* Set dithering if needed */
 	sun4i_tcon0_mode_set_dithering(tcon, sun4i_tcon_get_connector(encoder));
@@ -549,7 +558,14 @@ static void sun4i_tcon0_mode_set_rgb(struct sun4i_tcon *tcon,
 
 	tcon->dclk_min_div = tcon->quirks->dclk_min_div;
 	tcon->dclk_max_div = 127;
-	sun4i_tcon0_mode_set_common(tcon, mode);
+
+	/* Configure the dot clock */
+	clk_set_rate(tcon->dclk, mode->crtc_clock * 1000);
+
+	/* Set the resolution */
+	regmap_write(tcon->regs, SUN4I_TCON0_BASIC0_REG,
+		     SUN4I_TCON0_BASIC0_X(mode->crtc_hdisplay) |
+		     SUN4I_TCON0_BASIC0_Y(mode->crtc_vdisplay));
 
 	/* Set dithering if needed */
 	sun4i_tcon0_mode_set_dithering(tcon, connector);
-- 
2.39.2