linux-kernel - Re: [PATCH v4 00/16] mtd: spi-nor: add xSPI Octal DTR support

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Message-ID: <20200512184656.ksudjyeqbwv6jze6@ti.com>
Date:   Wed, 13 May 2020 00:16:58 +0530
From:   Pratyush Yadav <p.yadav@...com>
To:     <Tudor.Ambarus@...rochip.com>
CC:     <linux-mtd@...ts.infradead.org>, <vigneshr@...com>,
        <boris.brezillon@...labora.com>, <alexandre.belloni@...tlin.com>,
        <richard@....at>, <nsekhar@...com>, <linux-kernel@...r.kernel.org>,
        <Nicolas.Ferre@...rochip.com>, <Ludovic.Desroches@...rochip.com>,
        <broonie@...nel.org>, <miquel.raynal@...tlin.com>,
        <linux-spi@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 00/16] mtd: spi-nor: add xSPI Octal DTR support

On 12/05/20 11:29AM, Tudor.Ambarus@...rochip.com wrote:
> Hi, Vignesh,
> 
> > > The software reset procedure can't protect you from unexpected 
> > > resets, but
> > > the hardware with its optional reset pin can. Pratyush to confirm.
> > > 
> > > cut
> > > 
> > >>> Not recovering from unexpected resets is unacceptable. One should always
> > >>> prefer option 1/ and condition the entering in 2-2-2, 4-4-4 and 8-8-8
> > >>> with
> > >>> the presence of the optional RESET pin.
> > >> 
> > >> Totally agree with you on that one, but we know what happens in
> > >> practice...
> > > 
> > > What I proposed is to condition the entering in the state-full modes with
> > > the presence of the optional RESET pin. We would introduce an optional
> > > device tree property for the RESET pin. If hardware doesn't implement the
> > > optional RESET# signal, then we will not enter in the state-full modes.
> > 
> > Are you asking for dedicated SW controllable reset line or just an
> > indication from DT that OSPI reset line is connected to board level
> > soft/hard reset lines?
> 
> I don't see a need for the reset line to be SW controllable, a simple 
> indication from the device tree should be enough.

We already have the property "broken-flash-reset". Should we re-use it 
or should we have a opt-in property instead of an opt-out one?
 
> > 
> > Mandating SW controllable RESET line is bit of a stretch IMO... Board
> > design may not allow wasting dedicated pin due to lack of GPIOs perhaps..
> > 
> > For eg.: TI EVM has OSPI reset line connected to board level reset out.
> > This ensures any soft/warm/hard CPU reset will trigger OSPI Flash reset,
> > but there is no SW control that allows OSPI flash alone to be reset.
> > Isn't such a reset mechanism sufficient?
> > 
> 
> I think it is, yes.

-- 
Regards,
Pratyush Yadav
Texas Instruments India