On 12/18/22 23:24, Adam Ford wrote:
On Sat, Dec 17, 2022 at 10:33 PM Marek Vasut <marex@xxxxxxx> wrote:
On 12/18/22 05:23, Adam Ford wrote:
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.
I have these two attempts, both rejected:
https://patchwork.freedesktop.org/patch/475207/
https://patchwork.freedesktop.org/patch/496049/
I have some patches re-based to Jagan's latest branch. It doesn't
impact any drivers other than the new samsung-dsim driver, and it
doesn't touch any of the drm helper functions either. It adjusts hs
clock based on the connected device. I am not sure what the impact
will have on the attached Exynos devices, so I am expecting some
iterations. Right now it's working with my DSI83 chip, but I need to
get it working with my adv7535 part as well. On the older branch, I
was able to sync the ad7535 with a variety of resolutions using
different pixel clock rates.
Once I get it working again with my adv7535 and cleaned up, I'll
submit the patches to the drm group, and I'll CC you, Jagan and Marek
Szyprowski with a reference to Jagan's series so people wanting to try
it can apply it to his branch.
The negotiation has to happen between the host and the bridge/panel,
otherwise you won't be able to support bridge/panel devices which
require specific clock rate on the DSI. Only the bridge/panel driver
knows about such requirement.
