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

From: Bartosz Golaszewski
Date: Wed May 02 2018 - 06:45:46 EST


2018-05-01 12:29 GMT+02:00 Sekhar Nori <nsekhar@xxxxxx>:
> 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@xxxxxxxxxxxx>
>>>>
>>>> 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.

> --8<--
> commit 533d93703fa717fdf74c4fb711c868c4fdc8b475 (HEAD -> refs/heads/v4.18/nand-cs-simplification)
> Author: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
> AuthorDate: Mon Apr 30 10:24:42 2018 +0200
> Commit: Sekhar Nori <nsekhar@xxxxxx>
> 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@xxxxxxxxxxxx>
> Signed-off-by: Sekhar Nori <nsekhar@xxxxxx>
>
> 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?

> + uint32_t core_chipsel;
> +
> /* for packages using two chipselects */
> uint32_t mask_chipsel;
>
>

Thanks,
Bart