On 1/3/23 10:51, Alexander Stein wrote:
Hi Marek,
Am Sonntag, 18. Dezember 2022, 00:55:57 CET schrieb Marek Vasut:
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)
Mh, there is something bogus about this. Right now the PLL freq is set
depending on 'samsung,burst-clock-frequency' property. But this actually is
somehow depending on the number of lanes I configure. From the debug output
hs_clk and PLL freq are identical. AFAICS there is also no divider from PLL to
hs_clk in the register map.
Could it be that samsung,burst-clock-frequency is fPMS / 2 ?
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() ?
A working setup on a tianma,tm070jvhg33 display (1280x800) is:
samsung-dsim 32e10000.dsi: PLL freq 891000000, (p 3, m 99, s 0)
samsung-dsim 32e10000.dsi: hs_clk = 891000000, byte_clk = 111375000, esc_clk
= 18562500
sn65dsi83 2-002d: mode->clock: 68200
sn65dsi83 2-002d: mode bpp: 24
sn65dsi83 2-002d: ctx->dsi->lanes: 3
sn65dsi83 2-002d: samsung_dsim_set_pll: 0x37
Calculating backwards, sn64dsi83 is expecting a clock in the range of 275-280
MHz. But I fail to see a corresponding clock in the DSIM PLL configuration.
294.9 MHz, no ? 1280x800x24x60x1.2 / 3 / 2 = 294.9 .
