On Thu, Oct 31, 2024 at 10:35:27AM +0800, Liu Ying wrote:
> Hi Maxime,
>
> On 10/22/2024, Maxime Ripard wrote:
> > On Tue, Oct 22, 2024 at 02:13:57PM +0800, Liu Ying wrote:
> >> On 10/13/2024, Marek Vasut wrote:
> >>> On 10/11/24 8:18 AM, Liu Ying wrote:
> >>>> On 10/11/2024, Marek Vasut wrote:
> >>>>> 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 ?
> >>>>
> >>>> Mode validation is affected only for dual LVDS link mode.
> >>>> For single LVDS link mode, this patch does open more display
> >>>> modes read from the DDC I2C bus. The reason behind is that
> >>>> LVDS serial clock rate/pixel clock rate = 3.5 for dual LVDS
> >>>> link mode, while it's 7 for single LVDS link mode.
> >>>>
> >>>> In my system, "video_pll1" clock rate is assigned to 1.0395GHz
> >>>> in imx8mp.dtsi. For 1920x1080-60.00Hz with 148.5MHz pixel
> >>>> clock rate, "media_ldb" clock rate is 519.75MHz and
> >>>> "media_disp2_pix" clock rate is 148.5MHz, which is fine for
> >>>> dual LVDS link mode(x3.5). For newly opened up 1920x1080-59.94Hz
> >>>> with 148.352MHz pixel clock rate, "video_pll1" clock rate will
> >>>> be changed to 519.232MHz, "media_ldb" clock rate is 519.232MHz
> >>>> and "media_disp2_pix" clock rate is wrongly set to 519.232MHz
> >>>> too because "media_disp2_pix" clock cannot handle the 3.5
> >>>> division ratio from "video_pll1_out" clock running at
> >>>> 519.232MHz. See the below clk_summary.
> >>>
> >>> Shouldn't this patch help exactly with that ?
> >>
> >> No, it doesn't help but only makes clk_round_rate() called in
> >> LDB driver's .mode_valid() against 148.352MHz return 148.352MHz
> >> which allows the unexpected 1920x1080-59.94Hz display mode.
> >>
> >>>
> >>> It should allow you to set video_pll1_out to whatever is necessary by LDB first, fixate that frequency, and the LCDIFv3 would then be forced to use /7 divider from faster Video PLL1 , right ?
> >>
> >> Yes, it allows that for single-link LVDS use cases.
> >> And, __no__, for dual-link LVDS use cases because the
> >> video_pll1_out clock rate needs to be 2x the LVDS serial clock
> >> rate.
> >>
> >>>
> >>>> video_pll1_ref_sel 1 1 0 24000000 0 0 50000 Y deviceless no_connection_id
> >>>> video_pll1 1 1 0 519232000 0 0 50000 Y deviceless no_connection_id
> >>>> video_pll1_bypass 1 1 0 519232000 0 0 50000 Y deviceless no_connection_id
> >>>> video_pll1_out 2 2 0 519232000 0 0 50000 Y deviceless no_connection_id
> >>>> media_ldb 1 1 0 519232000 0 0 50000 Y deviceless no_connection_id
> >>>> media_ldb_root_clk 1 1 0 519232000 0 0 50000 Y 32ec0000.blk-ctrl:bridge@5c ldb
> >>>> deviceless no_connection_id
> >>>> media_disp1_pix 0 0 0 129808000 0 0 50000 N deviceless no_connection_id
> >>>> media_disp1_pix_root_clk 0 0 0 129808000 0 0 50000 N 32e80000.display-controller pix
> >>>> 32ec0000.blk-ctrl disp1
> >>>> deviceless no_connection_id
> >>>> media_disp2_pix 1 1 0 519232000 0 0 50000 Y deviceless no_connection_id
> >>>> media_disp2_pix_root_clk 1 1 0 519232000 0 0 50000 Y 32e90000.display-controller pix
> >>>> 32ec0000.blk-ctrl disp2
> >>>> deviceless no_connection_id
> >>>>
> >>>> Single LVDS link mode is not affected because "media_disp2_pix"
> >>>> clock can handle the 7 division ratio.
> >>>>
> >>>> To support the dual LVDS link mode, "video_pll1" clock rate needs
> >>>> to be x2 "media_ldb" clock rate so that "media_disp2_pix" clock
> >>>> can use 7 division ratio to achieve the /3.5 clock rate comparing
> >>>> to "media_ldb" clock rate. However, "video_pll1" is not seen by
> >>>> LDB driver thus not directly controlled by it. This is another
> >>>> reason why assigning a reasonable "video_pll1" clock rate in DT
> >>>> makes sense.
> >>>
> >>> I agree that _right_now_, the DT clock assignment is the only option.
> >>> I would like to see that DT part disappear and instead would prefer if the LDB/LCDIF could figure out the clock tree configuration themselves.
> >>
> >> I think we'll live with the assigned clock rate in DT, because the
> >> i.MX8MP LDB and Samsung MIPI DSI display pipelines need to share a
> >> video PLL, like I mentioned in comments for patch 2.
> >
> > Guys. There's 4 different discussions that look to be on the same topic,
> > and doing workarounds in the DT, DRM driver and clock driver for
> > something that looks like a broken clock.
>
> This is a bit complicated, because it is related to i.MX8MP MIPI DSI/
> LVDS/HDMI, i.MX93 MIPI DSI/LVDS/parallel display pipelines. Even
> i.MX6SX LVDS display pipeline is a bit related, since i.MX8MP/i.MX93/
> i.MX6SX LDBs share the same fsl-ldb.c driver.
>
> >
> > Could we have *somewhere* a proper description of what the problem is
> > exactly, so we can review it? Because at the moment, it's certainly not
> > helping.
>
> Can you please suggest a place where this could happen?
Here, by mail will be good. Worst case scenario using a ascii art.
Maxime
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