linux-kernel - Re: [PATCH v4 0/4] Watchdog: sp5100_tco: Replace cd6h/cd7h port I/O accesses with MMIO accesses

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Date:   Tue, 8 Feb 2022 15:20:25 +0100
From:   Jean Delvare <jdelvare@...e.de>
To:     Wolfram Sang <wsa@...nel.org>
Cc:     Terry Bowman <terry.bowman@....com>, linux@...ck-us.net,
        linux-watchdog@...r.kernel.org, linux-i2c@...r.kernel.org,
        andy.shevchenko@...il.com, rafael.j.wysocki@...el.com,
        linux-kernel@...r.kernel.org, wim@...ux-watchdog.org,
        rrichter@....com, thomas.lendacky@....com, sudheesh.mavila@....com,
        Nehal-bakulchandra.Shah@....com, Basavaraj.Natikar@....com,
        Shyam-sundar.S-k@....com, Mario.Limonciello@....com
Subject: Re: [PATCH v4 0/4] Watchdog: sp5100_tco: Replace cd6h/cd7h port I/O
 accesses with MMIO accesses

On Tue, 8 Feb 2022 11:00:31 +0100, Wolfram Sang wrote:
> > I'm still reviewing these, sorry. I only picked the first patch of the
> > series so that the sp5100_tco patches would build so I could test them.  
> 
> Ah, I see. I thought more than the first patch was needed for testing.

You need the full series to be on the safe side, otherwise there's a
risk that the two drivers will access the same registers using
different methods (legacy I/O vs MMIO) so there's no synchronization
and they could step on each other's toes.

However as I knew about this limitation, I was careful to not use the
SMBus driver while I was testing the watchdog driver :-)

-- 
Jean Delvare
SUSE L3 Support