[PATCH] OMAP: board-files: fix i2c_bus for tfp410

[Felipe Balbi]

Hi,

On Fri, Nov 16, 2012 at 04:27:01PM +0200, Tomi Valkeinen wrote:
> On 2012-11-16 15:51, Felipe Balbi wrote:
> > Hi,
> > 
> > On Fri, Nov 16, 2012 at 02:22:33PM +0200, Tomi Valkeinen wrote:
> >> The i2c handling in tfp410 driver, which handles converting parallel RGB
> >> to DVI, was changed in 958f2717b84e88bf833d996997fda8f73276f2af. The
> > 
> > commit summary should be added in () after commit hash. This would look
> > like:
> > 
> > 'was changed in 958f271 (OMAPDSS: TFP410: pdata rewrite).'
> 
> Yep.
> 
> >> patch changed what value the driver considers as invalid/undefined.
> >> Before the patch 0 was the invalid value, but as 0 is a valid bus
> >                   ^
> > 		  missing comma (,) character here.
> 
> Right.
> 
> >> number, the patch changed this to -1.
> >>
> >> However, the fact was missed that many board files do not define the bus
> >> number at all, thus it's left to 0. This causes the driver to fail to
> >> get the i2c bus, exiting from the driver's probe with an error, meaning
> >> that the DVI output does not work for those boards.
> >>
> >> This patch fixes the issue by changing the i2c_bus number field in the
> >> driver's platform data from u16 to int, and setting the bus number to -1
> >> in the board files for the boards that did not define the bus. The
> >> exception is devkit8000, for which the bus is set to 1, which is the
> >> correct bus for that board.
> >>
> >> The bug exists in v3.5+ kernels.
> >>
> >> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
> >> Reported-by: Thomas Weber <thomas at tomweber.eu>
> >> [for v3.5, v3.6 stable kernels]
> >> Cc: stable at vger.kernel.org
> > 
> > This format is peculiar. Usually people use:
> > 
> > Cc: stable at vger.kernel.org # v3.5 v3.6
> 
> Yes, I tried that. But my git send-email (1.7.10.4) rejects that line. I
> don't know if it's my setup, that particular git version, or what...

weird... I never had that problem, since git 1.6.x, I have never seen
that and I tend to upgrade rather frequently. I'm using 1.8.0 now and
have sent a few patches to stable recently with no problems.

> > To be fair, the whole i2c_bus_num looks like a big hackery introduced by
> > the way panel drivers are written for OMAP DSS.
> > 
> > TFP410 is an I2C client, not an OMAPDSS client. After a quick look at
> > the driver, there's is no such thing as a DSS bus, so looks like you
> > should have an I2C driver for TFP410 and the whole DSS stuff should be
> > just a list of clients, but not a struct bus at all.
> > 
> > The fact that you have to pass the I2C bus number down to the panel
> > driver is already a big indication of how wrong this is, IMHO.
> 
> Without going deeper in the dss device model problems, I would agree
> with you if this was about i2c panel, but this is not quite like that.
> 
> A panel controlled via i2c would be an i2c device. But TFP410 is not
> controlled via i2c. It's not really controlled at all except via
> power-down gpio. TFP410 doesn't need the i2c to be functional at all.

then why does it need the i2c adapter ? What is this power-down gpio ?
Should that be hidden under gpiolib instead ?

> The i2c lines do not even touch TFP410 chip, so to be precise, the i2c
> lines should not be TFP410's concern. The i2c lines come from the
> monitor and go to OMAP's i2c pins. But TFP410 driver is a convenient
> place to manage them.

fair enough... but who's actually using those i2c lines ? OMAP is the
I2C master, who's the slave ? It's something in the monitor, I assume...

IIUC, this I2C bus goes over the HDMI wire ?

> (As a side note, TFP410 _could_ be controlled via i2c, if it would've
> been setup so in the board hardware. That would be totally different
> thing, though, than what's discussed here.).
> 
> Anyway, this patch wasn't meant to fix dss device model problems. It's
> meant to fix a bug in the kernel.

I understand... should've added that this part wasn't related to
$SUBJECT.

-- 
balbi
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