linux-kernel - Re: [PATCH 1/2] dt-bindings: spi: fsl-lpspi: Option to allow stalling

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Date:   Mon, 1 Oct 2018 08:12:42 +0700
From:   Hieu Tran Dang <dangtranhieu2012@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     robh@...nel.org, linux-spi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: spi: fsl-lpspi: Option to allow stalling

Agree. I will create new patch which will just allow stalling by default.

Vào Th 6, 28 thg 9, 2018 vào lúc 05:47 Mark Brown <broonie@...nel.org> đã viết:
>
> On Wed, Sep 26, 2018 at 09:37:39PM +0700, Đặng Trần Hiếu wrote:
>
> > Default value of the register is to allow stalling (NOSTALL bit not
> > set) but the spi-fsl-lpspi driver defaults to setting the NOSTALL bit
> > in CFGR1. To me, it's more logical to leave the NOSTALL bit off with
> > fsl,nostall binding to set the bit but as I am not sure if there are
> > other drivers depending on the NOSTALL bit being set and not wanting
> > to break other drivers hence introduction of this binding to keep the
> > current default behavior.
>
> I can't see a situation where you'd actively want to report an error
> rather than stall, stalling allows us to handle things gracefully by
> restarting things.  Even if it's a timeout situation it sounds like we
> can unblock by reading/writing the stalled FIFO, and normally you'd be
> resetting the entire IP anyway.  I'd imagine the driver is this way
> either through an oversight or because there's some bug on some silicon
> which means that stalling breaks.
>
> Probably best to just always enable stalling unless I'm misreading
> things, if it is silicon bugs on some versions then either a whitelist
> or blacklist of SoCs to enable on (depending on how common the bug is)
> would be the way forwards - that way SoCs where it works get the benefit.