linux-kernel - Re: [PATCH 04/10] sata: hardreset: retry if phys link is down

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Date:   Sun, 15 Jan 2017 18:10:49 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Kevin Hilman <khilman@...nel.org>, Sekhar Nori <nsekhar@...com>,
        Patrick Titiano <ptitiano@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        David Lechner <david@...hnology.com>,
        linux-ide@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 04/10] sata: hardreset: retry if phys link is down

Hello,

On Fri, Jan 13, 2017 at 01:37:58PM +0100, Bartosz Golaszewski wrote:
> The sata core driver already retries to resume the link because some
> controllers ignore writes to the SControl register.
> 
> We have a use case with the da850 SATA controller where at PLL0
> frequency of 456MHz (needed to properly service the LCD controller)
> the chip becomes unstable and the hardreset operation is ignored the
> first time 50% of times.
> 
> Retrying just the resume operation doesn't work - we need to issue
> the phy/wake reset again to make it work.
> 
> If ata_phys_link_offline() returns true in sata_link_hardreset(),
> retry a couple times before really giving up.

I think it'd be better to implement the driver specific implementation
rather than changing the behavior for everybody.

Thanks.

-- 
tejun