linux-kernel - Re: [PATCH 01/12] mtd: nand: davinci: store the core chipselect number in platform data

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Message-ID: <16cff7a1-4353-5e03-fd0d-54cfe36a85ec@ti.com>
Date:   Wed, 2 May 2018 20:30:55 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
CC:     Kevin Hilman <khilman@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Tony Lindgren <tony@...mide.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        <linux-mtd@...ts.infradead.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 01/12] mtd: nand: davinci: store the core chipselect
 number in platform data

On Wednesday 02 May 2018 04:15 PM, Bartosz Golaszewski wrote:
> 2018-05-01 12:29 GMT+02:00 Sekhar Nori <nsekhar@...com>:
>> On Tuesday 01 May 2018 03:23 PM, Sekhar Nori wrote:
>>> On Tuesday 01 May 2018 02:55 PM, Sekhar Nori wrote:
>>>> On Monday 30 April 2018 01:54 PM, Bartosz Golaszewski wrote:
>>>>> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>>>>
>>>>> We have the 'ti,davinci-chipselect' property in the device tree, but
>>>>> when using platform data the driver silently uses the id field of
>>>>> struct platform_device as the chipselect. This is confusing and we
>>>>> almost broke the nand support again recently after converting the
>>>>> platform to common clock framework (which changed the device id in the
>>>>> clock lookup - the problem is gone now that we no longer acquire the
>>>>> clock in the nand driver.
>>>>>
>>>>> This patch adds a new filed - core_chipsel - to the platform_data.
>>>>
>>>> s/filed/field
>>>>
>>>>> Subsequent patches will convert the platforms to using this new field.
>>>>
>>>> Can you add a comment for this new field too, like how we have for most
>>>> other fields?
>>>>
>>>> Curious on what 'core' in core_chipsel means. Something to do with
>>>> chip-select offset we have on DA850?
>>>
>>> Looks like you may have just picked the terminology from DaVinci NAND
>>> driver (introduced back in 2009). But in this context, it means the
>>> 0-indexed chip-select number that of the asynchronous memory interface
>>> to which the NAND device is connected.
>>>
>>> So, may be a comment here will suffice.
>>
>> This is what I committed:
>>
> 
> I don't see it in your tree yet.

I pushed it out now. Wanted to do some basic testing.

> 
>> --8<--
>> commit 533d93703fa717fdf74c4fb711c868c4fdc8b475 (HEAD -> refs/heads/v4.18/nand-cs-simplification)
>> Author:     Bartosz Golaszewski <bgolaszewski@...libre.com>
>> AuthorDate: Mon Apr 30 10:24:42 2018 +0200
>> Commit:     Sekhar Nori <nsekhar@...com>
>> CommitDate: Tue May 1 15:57:47 2018 +0530
>>
>>     mtd: nand: davinci: store the core chipselect number in platform data
>>
>>     We have the 'ti,davinci-chipselect' property in the device tree, but
>>     when using platform data the driver silently uses the id field of
>>     struct platform_device as the chipselect. This is confusing and we
>>     almost broke the nand support again recently after converting the
>>     platform to common clock framework (which changed the device id in the
>>     clock lookup - the problem is gone now that we no longer acquire the
>>     clock in the nand driver.
>>
>>     This patch adds a new field - core_chipsel - to the platform_data.
>>     Subsequent patches will convert the platforms to using this new field.
>>
>>     Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>     Signed-off-by: Sekhar Nori <nsekhar@...com>
>>
>> diff --git a/include/linux/platform_data/mtd-davinci.h b/include/linux/platform_data/mtd-davinci.h
>> index f1a2cf655bdb..1bbfa27cccb4 100644
>> --- a/include/linux/platform_data/mtd-davinci.h
>> +++ b/include/linux/platform_data/mtd-davinci.h
>> @@ -56,6 +56,16 @@ struct davinci_nand_pdata {          /* platform_data */
>>         uint32_t                mask_ale;
>>         uint32_t                mask_cle;
>>
>> +       /*
>> +        * 0-indexed chip-select number of the asynchronous
>> +        * interface to which the NAND device has been connected.
>> +        *
>> +        * So, if you have NAND connected to CS3 of DA850, you
>> +        * will pass '1' here. Since the asynchronous interface
>> +        * on DA850 starts from CS2.
>> +        */
> 
> Maybe we should add that on all other DaVinci SoCs the async interface
> starts from CS0?

I just intended it to be an example (and chose the more confusing one).
I had already created the tree, not just pushed it out, so I went with
what I already have.

Thanks,
Sekhar