linux-kernel - [PATCH V4 6/6] drm: bridge: samsung-dsim: Support non-burst mode

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Message-Id: <20230506010933.170939-7-aford173@gmail.com>
Date:   Fri,  5 May 2023 20:09:33 -0500
From:   Adam Ford <aford173@...il.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     aford@...conembedded.com, Adam Ford <aford173@...il.com>,
        Chen-Yu Tsai <wenst@...omium.org>,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        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 V4 6/6] 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 a bridge chip.  This should have no impact
for people using burst-mode and setting the burst clock
rate is still required for those users.

Lastly, if the burst clock is 0, and the clock is set
from the pixel clock, cache the clock rate configured
from of samsung_dsim_set_pll in order to properly
calculate the blanking.

Signed-off-by: Adam Ford <aford173@...il.com>
Tested-by: Chen-Yu Tsai <wenst@...omium.org>
Tested-by: Frieder Schrempf <frieder.schrempf@...tron.de>
Reviewed-by: Frieder Schrempf <frieder.schrempf@...tron.de>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 21 +++++++++++++++++----
 include/drm/bridge/samsung-dsim.h     |  1 +
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index 1b98c4e040b0..b79db009c98b 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -654,16 +654,28 @@ static unsigned long samsung_dsim_set_pll(struct samsung_dsim *dsi,
 		reg = samsung_dsim_read(dsi, DSIM_STATUS_REG);
 	} while ((reg & DSIM_PLL_STABLE) == 0);
 
+	dsi->hs_clock = fout;
+
 	return fout;
 }
 
 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;
@@ -952,7 +964,7 @@ static void samsung_dsim_set_display_mode(struct samsung_dsim *dsi)
 	u32 reg;
 
 	if (dsi->mode_flags & MIPI_DSI_MODE_VIDEO) {
-		int byte_clk_khz = dsi->burst_clk_rate / 1000 / 8;
+		int byte_clk_khz = dsi->hs_clock / 1000 / 8;
 		int hfp = (m->hsync_start - m->hdisplay) * byte_clk_khz / m->clock;
 		int hbp = (m->htotal - m->hsync_end) * byte_clk_khz / m->clock;
 		int hsa = (m->hsync_end - m->hsync_start) * byte_clk_khz / m->clock;
@@ -1801,10 +1813,11 @@ 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);
diff --git a/include/drm/bridge/samsung-dsim.h b/include/drm/bridge/samsung-dsim.h
index 76ea8a1720cc..14176e6e9040 100644
--- a/include/drm/bridge/samsung-dsim.h
+++ b/include/drm/bridge/samsung-dsim.h
@@ -94,6 +94,7 @@ struct samsung_dsim {
 
 	u32 pll_clk_rate;
 	u32 burst_clk_rate;
+	u32 hs_clock;
 	u32 esc_clk_rate;
 	u32 lanes;
 	u32 mode_flags;
-- 
2.39.2