linux-kernel - Re: [PATCH v2 2/2] spi: amlogic-spifc-a1: add support for max_speed

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Message-ID: <c118f69d-db32-4544-83d5-14de089d5b51@sirena.org.uk>
Date:   Thu, 20 Jul 2023 16:46:06 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Martin Kurbanov <mmkurbanov@...rdevices.ru>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-spi@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-kernel@...r.kernel.org, kernel@...rdevices.ru
Subject: Re: [PATCH v2 2/2] spi: amlogic-spifc-a1: add support for
 max_speed_hz

On Thu, Jul 20, 2023 at 06:41:11PM +0300, Martin Kurbanov wrote:
> On 11.07.2023 10:25, Jerome Brunet wrote:

> >> +	ret = clk_set_rate(spifc->clk, freq);
> >> +	if (ret)
> >> +		return ret;

> >> +	spifc->curr_speed_hz = freq;

> > There is no guarantee that clk_set_rate() has set the rate you have
> > requested, at least not precisely. You should call clk_get_rate() here.

> Are you referring to a situation where there is a change in the rate due
> to a request from another client, such as a sibling driver with the same
> parent clock?

The clock may simply not be able to generate exactly the rate you
requested, the rate will be rounded to some value that the clock can
actually generate.

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