On Fri, Apr 16, 2021 at 04:37:48PM +0300, Andy Shevchenko wrote:
> On Fri, Apr 16, 2021 at 02:51:59PM +0200, Greg Kroah-Hartman wrote:
> > On Fri, Apr 16, 2021 at 03:31:16PM +0300, Andy Shevchenko wrote:
> > > The infamous commit c440eee1a7a1 ("Staging: fbtft: Switch to
> > > the GPIO descriptor interface") broke GPIO handling completely.
> > > It has already four commits to rectify and it seems not enough.
> > > In order to fix the mess here we:
> > >
> > > 1) Set default to "inactive" for all requested pins
> > >
> > > 2) Fix CS, RD, and WR pins polarity since it's active low and
> > > GPIO descriptor interface takes it into consideration from
> > > the Device Tree or ACPI
> > >
> > > 3) Fix RESET pin polarity in the places missed by the commit
> > > b918d1c27066 ("Staging: fbtft: Fix reset assertion when using gpio descriptor")
> > >
> > > 4) Consolidate chip activation (CS assert) under default
> > > ->reset() callback
> > >
> > > To summarize the expectations about polarity for GPIOs:
> > >
> > > #RD Low
> > > #WR Low
> > > #CS Low
> > > #RESET Low
> > > DC or RS High
> > > RW High
> > > Data 0..15 High
> > >
> > > See also Adafruit learning course [1] for the example of the schematics.
> > >
> > > While at it, drop unneeded NULL checks, since GPIO API is tolerant to that.
> > > At the end, update TODO to mark this job eventually done.
> > >
> > > [1]: https://learn.adafruit.com/adafruit-2-8-and-3-2-color-tft-touchscreen-breakout-v2/downloads
> >
> > Shouldn't this be broken up into "one patch per thing" from your list
> > above? Feels like you did a lot of different things all in the same
> > patch :(
>
> I am aware, but breaking to the things here will bring it to the state where
> the functionality is still broken in between. Another point is that the drop
> of unneeded checks will bring the modification of the same line in the code
> twice. Or if you look at 5), for instance, due to CS management breakage,
> fixing it w/o 5) will bring it to the weird case that previously handled CS
> due to lucky defaults from firmware or bootloader, suddenly won't work and
> nothing can help it. The split in this case would look like adding the CS
> handling to all drivers followed by removal all of them. I think it's ugly.
> And so on. Believe me, I really tried hard to split this, but it always
> becomes to undesired result.
>
> Any ideas how to split that we fix stuff in one commit?
Okay, item 3) can be split to a separate patch.
--
With Best Regards,
Andy Shevchenko
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