linux-kernel - Re: [PATCH v3 2/2] mtd: nand: raw: brcmnand: When oops in progress use pio and interrupt polling

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Date:   Fri, 17 May 2019 07:56:01 -0400
From:   Kamal Dasu <kdasu.kdev@...il.com>
To:     Richard Weinberger <richard.weinberger@...il.com>
Cc:     MTD Maling List <linux-mtd@...ts.infradead.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        Richard Weinberger <richard@....at>,
        LKML <linux-kernel@...r.kernel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH v3 2/2] mtd: nand: raw: brcmnand: When oops in progress
 use pio and interrupt polling

On Fri, May 17, 2019 at 4:12 AM Richard Weinberger
<richard.weinberger@...il.com> wrote:
>
> On Thu, May 16, 2019 at 6:42 PM Kamal Dasu <kdasu.kdev@...il.com> wrote:
> >
> > If mtd_oops is in progress, switch to polling during NAND command
> > completion instead of relying on DMA/interrupts so that the mtd_oops
> > buffer can be completely written in the assigned NAND partition.
>
> With the new flag the semantics change, as soon a panic write happened,
> the flag will stay and *all* future operates will take the polling/pio path.
>

Yes that is true.

> IMHO this is fine since the kernel cannot recover from an oops.
> But just to make sure we all get this. :-)
> An alternative would be to block all further non-panic writes.

Capturing the panic writes into an mtd device reliably is what the low
level driver is trying to do.If there are non panic writes they will
use pio and interrupt  polling  as well in this case.

> --
> Thanks,
> //richard

Thanks
Kamal