linux-kernel - [PATCH V3 6/7] drm: bridge: samsung-dsim: Support non-burst mode

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Message-Id: <20230502010759.17282-7-aford173@gmail.com>
Date:   Mon,  1 May 2023 20:07:58 -0500
From:   Adam Ford <aford173@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     marex@...x.de, aford@...conembedded.com,
        Adam Ford <aford173@...il.com>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Inki Dae <inki.dae@...sung.com>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V3 6/7] drm: bridge: samsung-dsim: Support non-burst mode

The high-speed clock is hard-coded to the burst-clock
frequency specified in the device tree.  However, when
using devices like certain bridge chips without burst mode
and varying resolutions and refresh rates, it may be
necessary to set the high-speed clock dynamically based
on the desired pixel clock for the connected device.

This also removes the need to set a clock speed from
the device tree for non-burst mode operation, since the
pixel clock rate is the rate requested from the attached
device like an HDMI bridge chip.  This should have no
impact for people using burst-mode and setting the burst
clock rate is still required for those users.

Signed-off-by: Adam Ford <aford173@...il.com>
Tested-by: Chen-Yu Tsai <wenst@...omium.org>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 99642230a54a..53099461cdc2 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -657,11 +657,21 @@ static unsigned long samsung_dsim_set_pll(struct samsung_dsim *dsi,
 
 static int samsung_dsim_enable_clock(struct samsung_dsim *dsi)
 {
-	unsigned long hs_clk, byte_clk, esc_clk;
+	unsigned long hs_clk, byte_clk, esc_clk, pix_clk;
 	unsigned long esc_div;
 	u32 reg;
+	struct drm_display_mode *m = &dsi->mode;
+	int bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
+
+	/* m->clock is in KHz */
+	pix_clk = m->clock * 1000;
+
+	/* Use burst_clk_rate if available, otherwise use the pix_clk */
+	if (dsi->burst_clk_rate)
+		hs_clk = samsung_dsim_set_pll(dsi, dsi->burst_clk_rate);
+	else
+		hs_clk = samsung_dsim_set_pll(dsi, DIV_ROUND_UP(pix_clk * bpp, dsi->lanes));
 
-	hs_clk = samsung_dsim_set_pll(dsi, dsi->burst_clk_rate);
 	if (!hs_clk) {
 		dev_err(dsi->dev, "failed to configure DSI PLL\n");
 		return -EFAULT;
@@ -1800,10 +1810,11 @@ static int samsung_dsim_parse_dt(struct samsung_dsim *dsi)
 			return PTR_ERR(pll_clk);
 	}
 
+	/* If it doesn't exist, use pixel clock instead of failing */
 	ret = samsung_dsim_of_read_u32(node, "samsung,burst-clock-frequency",
 				       &dsi->burst_clk_rate);
 	if (ret < 0)
-		return ret;
+		dsi->burst_clk_rate = 0;
 
 	ret = samsung_dsim_of_read_u32(node, "samsung,esc-clock-frequency",
 				       &dsi->esc_clk_rate);
-- 
2.39.2