Re: [PATCH v2 23/28] drm: omapdrm: Merge the dss_features and omap_dss_features structures

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On 13/05/17 14:12, Laurent Pinchart wrote:

>> Is it? You already use the dss compat string and soc_device_match to
>> figure out some versions. Isn't that a proper way to find out about the
>> SoC? But I agree that a more fine grained version management in each
>> individual driver would be better.
> 
> For OMAP2, OMAP4 or OMAP5 it shouldn't be too much of a problem, but OMAP3 
> would be more painful to handle. The following machine names are used.
> 
> "AM3505"
> "AM3517"
> "AM437x"
> "OMAP3430/3530"
> "OMAP3525"
> "OMAP3515"
> "OMAP3503"
> "OMAP3611"
> "OMAP3615/AM3715"
> "OMAP3621"
> "OMAP3630/DM3730"
> "AM3703"
> "DM3725"

Don't we need all those somewhere in any case? I mean, I presume all the
current OMAPDSS_VER_* defines are used somewhere. Which means that
somewhere, maybe in multiple different files, we need to handle some or
all of those.

For some features, perhaps we could move them to DT. If the feature is
about how DSS is integrated into the SoC, it might make sense to have
that in the DT, as a property for DSS, as it's not part of DSS itself.
If the data is missing, we could inject it into the DT at boot time,
based on the omap revision. Though I'm not sure if that would really
help that much.

I think the most annoying "feature" is the blank/porch register field
size change, that they made between OMAP3430 ES1 and ES2. And didn't
bother to change the DSS IP version...

But back to the topic... Are you sure this version detection should not
be centralized? If we have that many OMAP3 related devices already (btw,
AM4 is not really OMAP3 related, even if the DSS there is)... And if we
get one more. Does it mean we need to edit that same new device into
many places?

Then again, maybe it's better to handle that separately in each file
that requires the information, as sometimes all you need to know is that
it's DSS3 based, but sometimes you need to know that it's AM4's DSS vs
OMAP3's DSS.

> But I don't think that removing the extra platform devices is so urgent. I'd 
> rather do it when we're ready.
> 
> The omapdss driver needs major cleanup and refactoring, and that will result 
> in a large number of patches that will cause conflicts and be sources of 
> potential errors. I don't think that's avoidable. However, lots of those 
> cleanups will be independent from each other, so we can start merging the less 
> controversial ones as soon as they're ready. I'll take care of rebasing the 
> rest of the patches as needed.

Yes, no disagreements there. My hope is just that a series is as small
as possible. Or, that's not correct... A series does one change at a
time, e.g. here my problem was that the platform change was being done
at the same time as the feature change, interleaved.

I most likely will need to backport all these to v4.9 kernel. And then
manage new patches that will be applied on top of mainline and that v4.9
kernel. And I will gladly take any changes to patch serieses that
possibly make that work easier =).

 Tomi


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