linux-kernel - Re: [PATCH v2 1/2] nvme-apple: Reset controller during shutdown

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Message-ID: <20230119061452.GA17695@lst.de>
Date:   Thu, 19 Jan 2023 07:14:52 +0100
From:   Christoph Hellwig <hch@....de>
To:     Janne Grunau <j@...nau.net>
Cc:     Hector Martin <marcan@...can.st>, Sven Peter <sven@...npeter.dev>,
        Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Eric Curtin <ecurtin@...hat.com>, asahi@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org,
        linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] nvme-apple: Reset controller during shutdown

Folks, can you chime in if this comment makes sense?  I'd really
like to send the patches off to Jens before rc5.

On Wed, Jan 18, 2023 at 06:24:50AM +0100, Christoph Hellwig wrote:
> On Tue, Jan 17, 2023 at 07:25:00PM +0100, Janne Grunau wrote:
> > +		/*
> > +		 * Always reset the NVMe controller on shutdown. The reset is
> > +		 * required to shutdown the co-processor cleanly.
> > +		 */
> 
> Hmm.  This comment doesn't seem to match the discussion we had last
> week.  Which would be:
> 
> 		/*
> 		 * NVMe requires a reset before setting up a controller to
> 		 * ensure it is in a clean state.  For NVMe PCIe this is
> 		 * done in the setup path to be able to deal with controllers
> 		 * in any kind of state.  For for Apple devices, the firmware
> 		 * will not be available at that time and the reset will
> 		 * time out.  Thus reset after shutting the NVMe controller
> 		 * down and before shutting the firmware down.
> 		 */
---end quoted text---