linux-kernel - Re: [PATCH 2/2] spi: spidev: fix a max speed setting

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Message-ID: <20200220184201.GE3926@sirena.org.uk>
Date:   Thu, 20 Feb 2020 18:42:01 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Oleksandr Suvorov <oleksandr.suvorov@...adex.com>
Cc:     "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Oleksandr Suvorov <cryosay@...il.com>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        Igor Opanyuk <igor.opanyuk@...adex.com>,
        Philippe Schenker <philippe.schenker@...adex.com>
Subject: Re: [PATCH 2/2] spi: spidev: fix a max speed setting

On Thu, Feb 20, 2020 at 02:11:51PM +0000, Oleksandr Suvorov wrote:
> SPI_IOC_WR_MAX_SPEED_HZ command always sets spi->max_speed_hz
> to the initial value come from DT.

This is intentional.  It's doing a call to spi_setup() then restoring
the original value, the goal being just to run spi_setup() with the new
value - it's not really a good idea to change the maximum speed in the
first place.

> It leads to set a wrong max speed with IOCTL call.

In what way does it lead to the wrong speed being set?

> Fix the logic of a max speed assignment.

If the expectation is that the default speed should be changed for the
device this should be handled at the spidev level rather than in the
core.

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