[Letux-kernel] [PATCH v5 2/7] drm/ingenic: Add support for JZ4780 and HDMI output

Paul Cercueil paul at crapouillou.net
Mon Nov 8 19:53:24 CET 2021

Hi Nikolaus,

Le lun., nov. 8 2021 at 19:33:48 +0100, H. Nikolaus Schaller 
<hns at goldelico.com> a écrit :
> Hi Paul,
>>  Am 08.11.2021 um 18:49 schrieb Paul Cercueil <paul at crapouillou.net>:
>>>>  Variant 4: the variant #2 without the changes to the DTSI files.
>>>  Hm. If there is no cache and we can safely remove tight boundary 
>>> checking (by JZ_REG_LCD_SIZE1) for jz4725/40/70 (by not fixing 
>>> DTSI) why do we still need the max_register calculation from DTSI 
>>> specifically for jz4780 and at all?
>>  It's better to have the .max_register actually set to the proper 
>> value. Then reading the registers from debugfs 
>> (/sys/kernel/debug/regmap/) will print the actual list of registers 
>> without bogus values. If .max_register is set too high, it will end 
>> up reading outside the registers area.
> Ok, that is a good reason to convince me.
>>  On Ingenic SoCs such reads just return 0, but on some other SoCs it 
>> can lock up the system.
> Yes, I know some of these...
>>  So the best way forward is to have .max_register computed from the 
>> register area's size, and fix the DTSI with the proper sizes. Since 
>> your JZ4780 code needs to update .max_register anyway it's a good 
>> moment to add this patch, and the DTSI files can be fixed later (by 
>> me or whoever is up to the task).
> Well, it would already be part of my Variant #2 (untested). So I 
> could simply split it up further and you can test the pure dtsi 
> changes and apply them later or modify if that makes problems. Saves 
> you a little work. BTW: the jz4740 seems to have even less registers 
> (last register seems to be LCDCMD1 @ 0x1305005C).

Sure, if you want. Send the DTSI patch(es) separate from this patchset 

>>  Fixing the DTS is not a problem in any way, btw. We just need to 
>> ensure that the drivers still work with old DTB files, which will be 
>> the case here.
> Yes, that is right since the new values are smaller than the 
> originals.
> Ok, then let's do it that way.

Great. Waiting for your v6 then.


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