Re: [PATCH v12 00/18] drm: Add Samsung MIPI DSIM bridge

[Frieder Schrempf <frieder.schrempf@kontron.de>]

On 03.02.23 13:29, Rasmus Villemoes wrote:
> On 01/02/2023 23.00, Marek Vasut wrote:
>> On 1/30/23 13:45, Rasmus Villemoes wrote:
>>> On 27/01/2023 12.30, Marek Vasut wrote:
>>>> On 1/27/23 12:04, Jagan Teki wrote:
>>>
>>>>>> Thanks, but that's exactly what I'm doing, and I don't see any
>>>>>> modification of imx8mp.dtsi in that branch. I'm basically looking for
>>>>>> help to do the equivalent of
>>>>>>
>>>>>>     88775338cd58 - arm64: dts: imx8mm: Add MIPI DSI pipeline
>>>>>>     f964f67dd6ee - arm64: dts: imx8mm: Add eLCDIF node support
>>>>>>
>>>>>> for imx8mp in order to test those patches on our boards (we have two
>>>>>> variants).
>>>>>
>>>>> Marek, any help here, thanks.
>>>>
>>>> Try attached patch.
>>>
>>> Thanks. I removed the lcdif2 and ldb nodes I had added from Alexander's
>>> patch (94e6197dadc9 in linux-next) in order to apply it. I get a couple
>>> of errors during boot:
>>>
>>>    clk: /soc@0/bus@32c00000/mipi_dsi@32e60000: failed to reparent
>>> media_apb to sys_pll1_266m: -22
>>>
>>> and enabling a pr_debug in clk_core_set_parent_nolock() shows that this
>>> is because
>>>
>>>    clk_core_set_parent_nolock: clk sys_pll1_266m can not be parent of clk
>>> media_apb
>>>
>>> Further, the mipi_dsi fails to probe due to
>>>
>>>    /soc@0/bus@32c00000/mipi_dsi@32e60000: failed to get
>>> 'samsung,burst-clock-frequency' property
>>>
>>> All other .dtsi files seem to have those samsung,burst-clock-frequency
>>> and samsung,esc-clock-frequency properties, so I suppose those should
>>> also go into the imx8mp.dtsi and are not something that the board .dts
>>> file should supply(?).
>>
>> No, that samsung,esc-clock-frequency (should be some 10-20 MHz, based on
>> your panel/bridge) and samsung,burst-clock-frequency (that's the HS
>> clock) should go into board DT, as those are property of the attached
>> panel/bridge.
> 
> OK.
> 
> But I simply can't make that match what I see in that branch. For
> example, there's imx8mm-icore-mx8mm-ctouch2-of10.dts and
> imx8mm-icore-mx8mm-edimm2.2.dts which both seem to have a ti,sn65dsi84
> bridge, neither override the values defined in imx8mm.dtsi, which are
> 
>         samsung,burst-clock-frequency = <891000000>;
>         samsung,esc-clock-frequency = <54000000>;
> 
> and that 891MHz value seems to be out of range for the dsi84 bridge -
> under Recommended Operating Conditions, the data sheet says "DSI HS
> clock input frequency", min 40, max 500 MHz.

Please note that the value in samsung,burst-clock-frequency is double
the clock rate of the effective DSI HS clock. I can confirm that a
SN65DSI84 is able to work with the default settings in general. Still
the LVDS clock is derived from the DSI clock and the sn65dsi83 driver
calculates its PLL values expecting a DSI input clock matching the panel
mode. So you might have to tune this value.

> 
> There's also the "clk sys_pll1_266m can not be parent of clk media_apb".
> Are you sure about those assigned-clocks and assigned-clock-parents
> settings?
> 
> Rasmus
>