linux-kernel - Re: [PATCH v1] mtd: rawnand: meson: fix ready/busy command

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Message-ID: <20230605115033.7a9eb4c9@xps-13>
Date:   Mon, 5 Jun 2023 11:50:33 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Arseniy Krasnov <avkrasnov@...rdevices.ru>
Cc:     <oxffffaa@...il.com>, <kernel@...rdevices.ru>,
        <stable@...r.kernel.org>, <linux-mtd@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Liang Yang <liang.yang@...ogic.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Kevin Hilman <khilman@...libre.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>
Subject: Re: [PATCH v1] mtd: rawnand: meson: fix ready/busy command

Hi Arseniy,

avkrasnov@...rdevices.ru wrote on Mon, 5 Jun 2023 11:27:34 +0300:

> On 05.06.2023 11:17, Miquel Raynal wrote:
> > Hi Arseniy,
> > 
> > avkrasnov@...rdevices.ru wrote on Mon, 5 Jun 2023 09:39:40 +0300:
> >   
> >> Hello Miquel!
> >>
> >> I exclude this patch from the recent Meson patchset, as it is fix and not related to another patches.
> >> Also I think that I can split Meson patchset (from links below) in the following way:
> >> 1) Patch/patchset for OOB layout
> >> 2) Patchset for "nand-rb" logic (meson_nand.c + DT bindings)
> >> These two can also go independently:
> >> 3) https://lore.kernel.org/linux-mtd/20230601061850.3907800-6-AVKrasnov@sberdevices.ru/
> >> 4) https://lore.kernel.org/linux-mtd/20230601061850.3907800-7-AVKrasnov@sberdevices.ru/  
> > 
> > LGTM.  
> 
> I think we don't need this patch with new RB_INT value. I dive into conversations with Liang Yang - author of this driver. He said,
> that this define is "special" polling mode. Now I'm a little bit more experienced in NAND area, so IIUC we have two basic waiting modes:
> 1) Software, by sending status command, then polling reply from controller, and then finally send READ0 to exit status reading mode (nand_soft_waitrdy()).

This is useful...

> 2) By RB pin and interrupt - in this mode we send vendor specific command to the controller and it triggers interrupt on RB pin update.
>    In this case RB pin must be connected to the controller. This mode is already implemented by Liang Yang.

...this is useful...

> 
> Now, command with this new define works in the following way: we send status command, by instead of reading reply from it by software,
> controller itself checks RB pin and status ready bit in IO bus. Driver just waits on completion. After waiting we need to send
> READ0 command again to make controller leave status reading mode. I think this is like "intermediate" mode between software polling
> and hardware interrupt - there is no need to spin in loop, waiting for status ready bit, but still need to leave status mode by sending
> READ0 command. I'm not sure that we need this as third mode of waiting for command is done. May be at least not in this work on Meson driver,
> so I guess to drop this patch at  this moment and add 'nand_soft_waitrdy()' support.

...I agree we can skip this one.

Thanks,
Miquèl