Re: [PATCH 1/2] clk: imx: clk-imx8mp: Allow LDB serializer clock reconfigure parent rate

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On 10/10/24 7:22 AM, Liu Ying wrote:
On 10/09/2024, Marek Vasut wrote:
The media_ldb_root_clk supply LDB serializer. These clock are usually
shared with the LCDIFv3 pixel clock and supplied by the Video PLL on
i.MX8MP, but the LDB clock run at either x7 or x14 rate of the LCDIFv3
pixel clock. Allow the LDB to reconfigure Video PLL as needed, as that
results in accurate serializer clock.

Signed-off-by: Marek Vasut <marex@xxxxxxx>
---
Cc: Abel Vesa <abelvesa@xxxxxxxxxx>
Cc: Andrzej Hajda <andrzej.hajda@xxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxxx>
Cc: Fabio Estevam <festevam@xxxxxxxxx>
Cc: Isaac Scott <isaac.scott@xxxxxxxxxxxxxxxx>
Cc: Jernej Skrabec <jernej.skrabec@xxxxxxxxx>
Cc: Jonas Karlman <jonas@xxxxxxxxx>
Cc: Laurent Pinchart <Laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Maxime Ripard <mripard@xxxxxxxxxx>
Cc: Michael Turquette <mturquette@xxxxxxxxxxxx>
Cc: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
Cc: Peng Fan <peng.fan@xxxxxxx>
Cc: Pengutronix Kernel Team <kernel@xxxxxxxxxxxxxx>
Cc: Robert Foss <rfoss@xxxxxxxxxx>
Cc: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
Cc: Simona Vetter <simona@xxxxxxxx>
Cc: Stephen Boyd <sboyd@xxxxxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: imx@xxxxxxxxxxxxxxx
Cc: kernel@xxxxxxxxxxxxxxxxxx
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-clk@xxxxxxxxxxxxxxx
---
  drivers/clk/imx/clk-imx8mp.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/imx/clk-imx8mp.c b/drivers/clk/imx/clk-imx8mp.c
index 516dbd170c8a3..2e61d340b8ab7 100644
--- a/drivers/clk/imx/clk-imx8mp.c
+++ b/drivers/clk/imx/clk-imx8mp.c
@@ -611,7 +611,7 @@ static int imx8mp_clocks_probe(struct platform_device *pdev)
  	hws[IMX8MP_CLK_MEDIA_MIPI_PHY1_REF] = imx8m_clk_hw_composite("media_mipi_phy1_ref", imx8mp_media_mipi_phy1_ref_sels, ccm_base + 0xbd80);
  	hws[IMX8MP_CLK_MEDIA_DISP1_PIX] = imx8m_clk_hw_composite_bus_flags("media_disp1_pix", imx8mp_media_disp_pix_sels, ccm_base + 0xbe00, CLK_SET_RATE_PARENT);
  	hws[IMX8MP_CLK_MEDIA_CAM2_PIX] = imx8m_clk_hw_composite("media_cam2_pix", imx8mp_media_cam2_pix_sels, ccm_base + 0xbe80);
-	hws[IMX8MP_CLK_MEDIA_LDB] = imx8m_clk_hw_composite("media_ldb", imx8mp_media_ldb_sels, ccm_base + 0xbf00);
+	hws[IMX8MP_CLK_MEDIA_LDB] = imx8m_clk_hw_composite_bus_flags("media_ldb", imx8mp_media_ldb_sels, ccm_base + 0xbf00, CLK_SET_RATE_PARENT);

This patch would cause the below in-flight LDB bridge driver
patch[1] fail to do display mode validation upon display modes
read from LVDS to HDMI converter IT6263's DDC I2C bus.

Why ?

Also, please Cc me on fsl-ldb.c patches.

Unsupported display modes cannot be ruled out.  Note that
"media_ldb" is derived from "video_pll1_out" by default as the
parent is set in imx8mp.dtsi.  And, the only 4 rates supported
by "video_pll1" are listed in imx_pll1443x_tbl[] - 1.0395GHz,
650MHz, 594MHz and 519.75MHz.
I disagree with this part, since commit b09c68dc57c9 ("clk: imx: pll14xx: Support dynamic rates") the 1443x PLLs can be configured to arbitrary rates which for video PLL is desirable as those should produce accurate clock.



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