On Sat, Dec 17, 2022 at 5:56 PM Marek Vasut <marex@xxxxxxx> wrote: > > On 12/16/22 14:25, Alexander Stein wrote: > Hi, > > [...] > > > Oh, nice, thanks for the pointer. When setting > >> samsung,burst-clock-frequency = <668250000>; > > in imx8mm.dtsi > > I get a non-flickering display using 4 lanes. Although admittedly this is just > > random guessing. I'm not sure which clock exactly has to be in the range > > CHA_DSI_CLK_RANGE is configured to. With 4 lanes SN65DSI84 is configured for > > 205-210 MHz (0x29), while I get these PLL PMS settings on DSIM: > >> samsung-dsim 32e10000.dsi: PLL freq 668250000, (p 4, m 99, s 0) > >> samsung-dsim 32e10000.dsi: hs_clk = 668250000, byte_clk = 83531250, esc_clk > > = 16706250 > > If I recall it right, minimum PLL frequency is: > > fPMS=1.2*width*height*bpp*fps=1.2*800*480*24*60=663.5 MHz > > the link frequency is then > > fHS=fPMS/lanes/2=82.9 MHz (on the DDR clock lane) > > So DSI83 should be in the range of 80..85 MHz input clock if I calculate > this right. Can you check what is the value of mode->clock, the > mipi_dsi_panel_format_to_bpp() return value, ctx->dsi->lanes in dsi83 > sm65dsi83_get_dsi_range() ? > > > AFAICS DSIM bridge is configurung hs_clk, byte_clk and esc_clk just from DT > > properties, while SN65DSI84 is using display mode and number of lanes. > > > > Is it expected that the DSIM PLL frequencies are set in DT for a specific > > bridge/display setup? > > No, there should be negotiation between the host and bridge/panel, I > tried to propose two variants, but they were all rejected. For one of Jagan's previous revisions, I added some code to let the PHY auto adjust the frequencies instead of being fixed. NXP had this in their downstream kernel, but with this patch and another, I was able to set a variety of pixel clocks from my HDMI monitor and my DSI83. I haven't had time to re-base my work on Jagan's latest work, but you can link to the patch I did for the older stuff here: https://github.com/aford173/linux/commit/e845274b0f22ba3b24813ffd6bb3cb88ab4b67e4 and https://github.com/aford173/linux/commit/3f90057eb608f96d106029ef639813475241936f I've been traveling a lot lately, so I haven't had time to evaluate his series, but I hope to get something like those re-based once the DSI stuff has been accepted. adam
