linux-kernel - Re: [PATCH 2/7] spi: fsi: Fix clock running too fast

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Message-ID: <660034d2-c808-3a4b-6ecc-be1769e8a017@linux.ibm.com>
Date:   Thu, 20 Aug 2020 16:06:07 -0500
From:   Eddie James <eajames@...ux.ibm.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, joel@....id.au,
        bradleyb@...ziesquirrel.com, robh+dt@...nel.org, arnd@...db.de
Subject: Re: [PATCH 2/7] spi: fsi: Fix clock running too fast


On 8/20/20 12:12 PM, Mark Brown wrote:
> On Thu, Aug 20, 2020 at 12:02:23PM -0500, Eddie James wrote:
>> From: Brad Bishop <bradleyb@...ziesquirrel.com>
>>
>> Use a clock divider tuned to a 200MHz FSI clock.  Use of the previous
>> divider at 200MHz results in corrupt data from endpoint devices. Ideally
>> the clock divider would be calculated from the FSI clock, but that
>> would require some significant work on the FSI driver.
> Presumably this divider was chosen for FSI clocks that aren't 200MHz -
> how will those be handled?


They aren't handled at the moment, but 200MHz FSI represents the worst 
case, as it's the maximum. Slower FSI clocks will simply result in 
slower SPI clocks.

Thanks,

Eddie