linux-kernel - Re: [PATCH v3 00/27] memory: omap-gpmc: mtd: nand: Support GPMC NAND on non-OMAP platforms

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Message-ID: <566004F1.2040806@ti.com>
Date:	Thu, 3 Dec 2015 14:31:37 +0530
From:	Roger Quadros <rogerq@...com>
To:	Brian Norris <computersforpeace@...il.com>, <tony@...mide.com>
CC:	<dwmw2@...radead.org>, <ezequiel@...guardiasur.com.ar>,
	<javier@...hile0.org>, <fcooper@...com>, <nsekhar@...com>,
	<linux-mtd@...ts.infradead.org>, <linux-omap@...r.kernel.org>,
	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 00/27] memory: omap-gpmc: mtd: nand: Support GPMC NAND
 on non-OMAP platforms

On 03/12/15 11:52, Brian Norris wrote:
> Hi,
> 
> On Thu, Dec 03, 2015 at 11:38:14AM +0530, Roger Quadros wrote:
>> On 03/12/15 10:39, Brian Norris wrote:
>>> On Fri, Sep 18, 2015 at 05:53:22PM +0300, Roger Quadros wrote:
>>>> We do a couple of things in this series which result in
>>>> cleaner device tree implementation, faster perfomance and
>>>> multi-platform support. As an added bonus we get new GPI/Interrupt pins
>>>> for use in the system.
>>>>
>>>> - Establish a custom interface between NAND and GPMC driver. This is
>>>> needed because all of the NAND registers sit in the GPMC register space.
>>>> Some bits like NAND IRQ are even shared with GPMC.
>>>>
>>>> - Remove NAND IRQ handling from omap-gpmc driver, share the GPMC IRQ
>>>> with the omap2-nand driver and handle NAND IRQ events in the NAND driver.
>>>> This causes performance increase when using prefetch-irq mode.
>>>> 30% increase in read, 17% increase in write in prefetch-irq mode.
>>>>
>>>> - Clean up device tree support so that omap-gpmc IP and the omap2 NAND
>>>> driver can be used on non-OMAP platforms. e.g. Keystone.
>>>>
>>>> - Implement GPIOCHIP + IRQCHIP for the GPMC WAITPINS. SoCs can contain
>>>> 2 to 4 of these and most of them would be unused otherwise. It also
>>>> allows a cleaner implementation of NAND Ready pin status for the NAND driver.
>>>>
>>>> - Implement GPIOlib based NAND ready pin checking for OMAP NAND driver.
>>>>
>>>> This series is available at
>>>> git@...hub.com:rogerq/linux.git
>>>> in branch
>>>> for-v4.4/gpmc-v3
>>>>
>>>> cheers,
>>>> -roger
>>>>
>>>> Changelog:
>>>> v3:
>>>> -Fixed and tested NAND using legacy boot on omap3-beagle.
>>>> -Support rising and falling edge interrupts on WAITpins.
>>>> -Update DT node of all gpmc users.
>>>
>>> The MTD stuff looks mostly good to me know. I've made all my comments
>>> for now, but I'm not sure how you're going to end up rebasing/splitting
>>> and what you're going to do with the irqchip removal, so I'll refrain
>>> from ack's for now. Hopefully I can either ack or merge v4.
>>
>> I'll retain the irqchip model for now and send a v4 with all comments
>> addressed and better subsystem wise patch split.
>>
>>>
>>> I brought it up on one other patch, but it's not really clear to me what
>>> the split is on board file vs. device tree handling, since you seem to
>>> have a combination of both (i.e., platform data that passes along device
>>> nodes). What's the plan on that?
>>
>> Platform data no longer passes device nodes. We're either true device tree
>> or plain legacy. The deprecated fields are no longer used once the series is
>> applied.
> 
> Well, they're still sorta used (you assign info->of_node =
> pdata->of_node, for instance). As dicussed in the other thread, I think
> we can avoid the deprecation part and just kill the fields though, and
> that would make things clearer.
> 
>>> And of course, there's the question of how exactly to merge this, given
>>> the:
>>> (1) conflicts already existing in the MTD dev tree
>>
>> I'll rebase the series on top of MTD dev tree.
> 
> OK. FWIW, we so far only need to base them on commit a61ae81a1907 ("mtd:
> nand: drop unnecessary partition parser data"). Maybe when queueing up a
> branch, that'd be the best starting point for Tony, so he doesn't need
> to have all of MTD's stuff in his tree too? I can set up a signed tag or
> something, if that would be helpful.
> 
> But for sending patches, the latest l2-mtd.git is fine too.
> 
>>> (2) this touches several trees, often in the same patch and
>>
>> I'll try my best to split the patches but not sure if this could be 100%
>> clean split without functional breakage.
>>
>>> (3) even if the patches were split out a little better into MTD and
>>>     non-MTD stuff, I think there would still be dependencies such that
>>>     we'd need at least 1 (probably 2) cross merges to get it all
>>>     straight
>>
>> That is correct.
>> Is it OK if functionality breaks if for example only MTD changes are considered?
> 
> I think I may have misunderstood the branch proposal. If Tony queues up:
> 
>   l2-mtd.git (or just up to commit a61ae81a1907)
>   +
>   your patches
> 
> and I pull that back into l2-mtd.git as well, then we don't need to
> worry about patches that touch multiple "trees". Just do whatever makes
> things clearest, including disregarding some of my comments along the
> line of (3).

Tony,

Are you fine with this?

cheers,
-roger
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