Re: [PATCH v2 2/3] drm/omapdrm: Work-a-round for errata i734 (LCD1 Gamma) in DSS dispc

[Jyri Sarha <jsarha@ti.com>]

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On 05/23/16 18:06, Tomi Valkeinen wrote:
>> For gamma tables to work on LCD1 the GFX plane has to be used at least
>> > once after DSS HW has come out of reset. The work-a-round sets up a
>> > minimal LCD setup with GFX plane and waits for one vertical sync irq
>> > before disabling the setup and continuing with the context
>> > restore. The physical outputs are gated during the operation. This
>> > work-a-round requires that gamma table's LOADMODE is set to 0x2 in
>> > DISPC_CONTROL1 register.
> This LOADMODE comment is a bit odd. You should say why, and how it's
> handled, and what's "0x2". But then, I'm not sure if the whole comment
> is needed at all. The driver is made to work only with LOADMODE=2.
> 

It is there also in the comment and my point is to notify that if the
gamma support is ever changed to use some other mode, the workaround
needs to change too.

It is pretty hard to draw the line to how deep in details one should go
in comments or commit descriptions. I added the register name so that
someone is interested he can find the full description of the LOADMODE
from TRM using that as a key word.

I think I wont mention the LOADMODE in the description but leave it on
the code comments.

> Maybe the real point here is that the WA needs to happen after the
> initial DSS register config.
> 

I think that detail should be in the code comments, if it is needed at all.

BR,
Jyri


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