linux-kernel - Re: [PATCH v3] scsi: ufs: Cleanup completed request without interrupt notification

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Message-ID: <912623e8-5915-8380-f39a-fac7b5868a6d@acm.org>
Date:   Tue, 14 Jul 2020 21:00:44 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Avri Altman <Avri.Altman@....com>,
        Stanley Chu <stanley.chu@...iatek.com>
Cc:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kuohong.wang@...iatek.com" <kuohong.wang@...iatek.com>,
        "peter.wang@...iatek.com" <peter.wang@...iatek.com>,
        "chun-hung.wu@...iatek.com" <chun-hung.wu@...iatek.com>,
        "andy.teng@...iatek.com" <andy.teng@...iatek.com>,
        "chaotian.jing@...iatek.com" <chaotian.jing@...iatek.com>,
        "cc.chou@...iatek.com" <cc.chou@...iatek.com>
Subject: Re: [PATCH v3] scsi: ufs: Cleanup completed request without interrupt
 notification

On 2020-07-13 01:10, Avri Altman wrote:
> Artificially injecting errors is a very common validation mechanism,
> Provided that you are not breaking anything of the upper-layers,
> Which I don't think you are doing.

Hi Avri,

My concern is that the code that is being added in the abort handler
sooner or later will evolve into a duplicate of the regular completion
path. Wouldn't it be better to poll for completions from the timeout
handler by calling ufshcd_transfer_req_compl() instead of duplicating
that function?

>>> In section 7.2.3 of the UFS specification I found the following about how
>>> to process request completions: "Software determines if new TRs have
>>> completed since step #2, by repeating one of the two methods described in
>>> step #2. If new TRs have completed, software repeats the sequence from
>>> step #3." Is such a loop perhaps missing from the Linux UFS driver?
>
> Could not find that citation.
> What version of the spec are you using?

That quote comes from the following document: "Universal Flash Storage
Host Controller Interface (UFSHCI); Version 2.1; JESD223C; (Revision of
JESD223B, September 2013); MARCH 2016".

Bart.