linux-kernel - Re: [PATCH v5 09/15] scsi: ufs: add error recovery after DL NAC error

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Date:	Tue, 1 Mar 2016 15:51:55 +0800
From:	Hannes Reinecke <hare@...e.de>
To:	Yaniv Gardi <ygardi@...eaurora.org>,
	James.Bottomley@...senPartnership.com
Cc:	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, santoshsy@...il.com,
	linux-scsi-owner@...r.kernel.org,
	Subhash Jadavani <subhashj@...eaurora.org>,
	Vinayak Holikatti <vinholikatti@...il.com>,
	"James E.J. Bottomley" <JBottomley@...n.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>
Subject: Re: [PATCH v5 09/15] scsi: ufs: add error recovery after DL NAC error

On 02/28/2016 09:32 PM, Yaniv Gardi wrote:
> Some vendor's UFS device sends back to back NACs for the DL data frames
> causing the host controller to raise the DFES error status. Sometimes
> such UFS devices send back to back NAC without waiting for new
> retransmitted DL frame from the host and in such cases it might be
> possible the Host UniPro goes into bad state without raising the DFES
> error interrupt. If this happens then all the pending commands would
> timeout only after respective SW command (which is generally too
> large).
> 
> This change workarounds such device behaviour like this:
> - As soon as SW sees the DL NAC error, it would schedule the error
>   handler
> - Error handler would sleep for 50ms to see if there any fatal errors
>   raised by UFS controller.
>    - If there are fatal errors then SW does normal error recovery.
>    - If there are no fatal errors then SW sends the NOP command to
>      device to check if link is alive.
>        - If NOP command times out, SW does normal error recovery
>        - If NOP command succeed, skip the error handling.
> 
> If DL NAC error is seen multiple times with some vendor's UFS devices
> then enable this quirk to initiate quick error recovery and also
> silence related error logs to reduce spamming of kernel logs.
> 
> Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
> Signed-off-by: Yaniv Gardi <ygardi@...eaurora.org>
> 
> ---
>  drivers/scsi/ufs/ufshcd.c | 93 +++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/scsi/ufs/ufshci.h |  2 +
>  2 files changed, 95 insertions(+)
> 
Reviewed-by: Hannes Reinecke <hare@...e.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@...e.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)