Re: [PATCH 0/8 RFC] OMAP: GPIO: Split OMAP1 and OMAP2PLUS

Kevin Hilman
2010-04-19T14:31:26Z

"Varadarajan, Charulatha" <charu@ti.com> writes:

>> -----Original Message-----
>> From: Kevin Hilman [mailto:khilman@deeprootsystems.com]
>> Sent: Wednesday, April 07, 2010 4:01 AM
>> To: Varadarajan, Charulatha
>> Cc: linux-omap@vger.kernel.org; Nayak, Rajendra; paul@pwsan.com; tony@atomide.com
>> Subject: Re: [PATCH 0/8 RFC] OMAP: GPIO: Split OMAP1 and OMAP2PLUS
>>
>> Charulatha V <charu@ti.com> writes:
>>
>> > This patch series is in preparation to adapt GPIO to HWMOD FW.
>> > It creates OMAP architecture specific gpio files to handle
>> > SoC specific gpio_init. The common plat-omap/gpio.c handles all
>> > common GPIO APIs.
>> >
>> > OMAP2PLUS GPIO module is implemented as early platform device and
>> > OMAP1 GPIO is still handled in old way via gpio_init from board files.
>> >
>> > Save/restore context, gpio_prepare_for_retention and
>> > gpio_resume_after_retention APIs are also handled in plat-omap layer.
>> > These APIs are currently not used in OMAP1, but still they might
>> > become common for different OMAP architectures in the future.
>> > Hence they are handled in plat-omap layer. If they need to be moved
>> > to mach-omap2 layer, additional patches may be sent during
>> > next version of this patch series.
>> >
>> > This patch series is generated on top of linux-omap-2.6 branch: master
>> > and tested on 3430SDP, 4430SDP & zoom3.
>>
>> I have many problems with this series, but without going into the
>> specifics of each patch, I have a big problem with the general
>> approach being taken here.
>>
>> You say this is in preparation for adaptation to hwmod, but in fact,
>> this series is duplicating a lot of the work you would get for free by
>> starting with hwmod.
>>
>> You're generating a bunch of code that will be completely thrown away
>> with a hwmod conversion. Instead, you should *start* by using hwmod +
>> omap_device to generate the platform_devices for you. Doing this, you
>> will drop patches 2, 3 and 4 entirely (they are mostly identical
>> anyways, except for the search-and-replace) and also eliminate the
>> need for patch 5.
>>
>> What is needed here is a way to introduce the platform_device
>> conversion without introducing signifcant functional changes at the
>> same time. Here's a proposal to do that, and which should also be
>> considerably easier to review for sanity:
>>
>> - use hwmod + omap_device to generate (early) platform_devices
>> - modify plat-omap/gpio.c to use base addr and IRQ from platform_device
>> - modify plat-omap/gpio.c to get clocks based on 'struct device'
>>
>> For an example, you can see the pm-wip/hwmods branch in my tree for
>> how this was done for UART and the pm-wip/mmc branch for how this was
>> done for MMC.
>
> I agree that most of the code would be thrown away once HWMOD comes into picture. Since hwmod patches would be gated for a long time, we decided to first proceed in pushing "GPIO as early init" patch series to mainline first, so that hwmods branch and mainline would not differ much.
>
> Tony/Kevin,
>
> Please suggest which approach is better
> 1. to send early init GPIO patches to mainline due to above mentioned reason (or)
> 2. to make GPIO as a HWMOD FW adapted driver and gate it in hwmods branch.

Please do option 2 to avoid massive duplication of work.

Kevin