Re: [PATCH v2 1/8] sh-pfc: Add OF support

[Guennadi Liakhovetski <g.liakhovetski@gmx.de>]

Hi Laurent

On Wed, 9 Jan 2013, Laurent Pinchart wrote:

> Support device instantiation through the device tree. The compatible
> property is used to select the SoC pinmux information.
> 
> Set the gpio_chip device field to the PFC device to enable automatic
> GPIO OF support.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> Cc: devicetree-discuss@lists.ozlabs.org

This whole pinctrl mega-series is a very welcome improvement to the 
sh-/r-mobile GPIO framework, and is very well done IMHO! But, 
unfortunately, as discussed with you privately yesterday, there is still a 
problem with pinctrl DT support on sh73a0, which will, probably, enforce 
an update to one or several of patches from this lot. To explain to other 
readers, on sh73a0 pin numbers are not contiguous, they are sparse. 
When pins are referred to from C code, macro names are used, which are 
then correctly decoded to respective positions in pin descriptor tables. 
Whereas with DT, pins are referred to from .dts files using their physical 
numbers, which then refer to either wrong or missing entries in those 
tables.

I do not know where this problem should be solved best - either in 
descriptor tables, or in DT handling code, so, I don't know which patches 
would be affected. Don't think you'll want to keep the one-to-one 
index-to-pin mapping by also making pin-descriptor arrays sparse, so, so 
far I only see one possibility to fix this - by using the .enum_id field 
from struct sh_pfc_pin instead of just the index - both in  C and in DT 
case, and those .enum_id values will have to provide physical pin numbers 
instead of plane indices. That way you'd have to update at least 
drivers/pinctrl/sh-pfc/pfc-sh73a0.c and the sh_pfc_map_gpios() function in 
drivers/pinctrl/sh-pfc/pinctrl.c.

Anyway, I'm sure you'll find a suitable solution of this problem and for 
now I'll let Simon decide which patches he wants to apply and which ones 
he'd prefer to hold back;-)

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/