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

Message ID 20230502010759.17282-7-aford173@gmail.com (mailing list archive)
State New, archived
Headers show
Series drm: bridge: samsung-dsim: Support variable clocking | expand

Commit Message

Adam Ford May 2, 2023, 1:07 a.m. UTC 
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@gmail.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

Comments

Frieder Schrempf May 3, 2023, 3:43 p.m. UTC | #1 
On 02.05.23 03:07, Adam Ford wrote:
> 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@gmail.com>
> Tested-by: Chen-Yu Tsai <wenst@chromium.org>

Tested on Kontron BL i.MX8MM with SN65DSI84 and ADV7535 bridges.

Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
diff mbox series

Patch

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);