linux-kernel - Re: [PATCH v3 0/4] Watchdog: sp5100_tco: Replace cd6h/cd7h port I/O accesses with MMIO accesses

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Message-ID: <dda39f1f-b683-35ac-d810-d4759c4f8448@amd.com>
Date:   Wed, 19 Jan 2022 11:33:55 -0600
From:   Terry Bowman <Terry.Bowman@....com>
To:     Jean Delvare <jdelvare@...e.de>
Cc:     linux@...ck-us.net, linux-watchdog@...r.kernel.org,
        jdelvare@...e.com, linux-i2c@...r.kernel.org, wsa@...nel.org,
        andy.shevchenko@...il.com, rafael.j.wysocki@...el.com,
        linux-kernel@...r.kernel.org, wim@...ux-watchdog.org,
        rrichter@....com, thomas.lendacky@....com,
        Nehal-bakulchandra.Shah@....com, Basavaraj.Natikar@....com,
        Shyam-sundar.S-k@....com, Mario.Limonciello@....com
Subject: Re: [PATCH v3 0/4] Watchdog: sp5100_tco: Replace cd6h/cd7h port I/O
 accesses with MMIO accesses



On 1/19/22 9:30 AM, Jean Delvare wrote:
> Hi Terry,
> 
> On Tue, 18 Jan 2022 14:22:30 -0600, Terry Bowman wrote:
>> This series uses request_mem_region() to synchronize accesses to the MMIO
>> registers mentioned above. request_mem_region() is missing the retry
>> logic in the case the resource is busy. As a result, request_mem_region()
>> will fail immediately if the resource is busy. The 'muxed' variant is
>> needed here but request_muxed_mem_region() is not defined to use.  I will
>> follow up with another patch series to define the
>> request_muxed_mem_region() and use in both drivers.
> 
> Shouldn't this be done the other way around, first introducing
> request_muxed_mem_region() and then using it directly in both drivers,
> rather than having a temporary situation where a failure can happen?
> 
> As far as I'm concerned, the patch series you just posted are
> acceptable only if request_muxed_mem_region() gets accepted too.
> Otherwise we end up with the situation where a driver could randomly
> fail.
> 

Hi Jean,
                                                                      
I considered sending the request_muxed_mem_region() patch series first but 
was concerned the patch might not be accepted without a need or usage. I 
didn't see an obvious path forward for the order of submissions because of 
the dependencies. 

I need to make the review easy for you and the other maintainers. I can 
send the request_muxed_mem_region() single patch series ASAP if you like. 
Then I change the request_mem_region() -> request_muxed_mem_region() as 
needed in the piix4_smbus v3 and sp5100_tco v4 and add dependency line as 
well? Is their a risk the driver patches will take 2 merge windows before 
added to the tree ? Is there anything I can do to avoid this?

Regards,
Terry