linux-kernel - RE: [PATCH] spi: cadence-quadspi: Add upper limit safety check to baudrate divisor

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Date:   Thu, 24 Nov 2022 06:53:54 -0500
From:   Nathan Barrett-Morrison <nathan.morrison@...esys.com>
To:     broonie@...nel.org
Cc:     greg.malysa@...esys.com, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org, nathan.morrison@...esys.com
Subject: RE: [PATCH] spi: cadence-quadspi: Add upper limit safety check to baudrate divisor

Hi Mark & Dhruva,

Your understanding is correct.  This is just checking if the divisor field has exceed the bit field's full scale (0xF) in this case.  This was observed when we had a reference block of 500MHz and a max SPI clock of 10MHz setting.

500000000/2*10000000 = 25
25 > 0xF (15)

Would you like me to add a dev_err (or such) bailout error condition and resubmit?

Sincerely,
Nathan