linux-kernel - Re: [PATCH] spi/rockchip: Make sure spi clk is on in rockchip_spi_set

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Message-ID: <20160305044531.GB18327@sirena.org.uk>
Date:	Sat, 5 Mar 2016 13:45:31 +0900
From:	Mark Brown <broonie@...nel.org>
To:	"Huang, Tao" <huangtao@...k-chips.com>
Cc:	Huibin Hong <huibin.hong@...k-chips.com>,
	linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
	"shawn.lin" <shawn.lin@...nel-upstream.org>,
	linux-rockchip@...ts.infradead.org,
	Addy Ke <addy.ke@...k-chips.com>
Subject: Re: [PATCH] spi/rockchip: Make sure spi clk is on in
 rockchip_spi_set_cs

On Fri, Feb 26, 2016 at 10:31:50AM +0800, Huang, Tao wrote:

> You misunderstand me. I talk about spi_setup, as
> Documentation/spi/spi-summary, which would normally be called from
> probe() before the first I/O is done to the device.
> spi_setup will call spi_set_cs(spi, false), which introduced with commit
> 1a7b7ee72c21 ("spi: Ensure that CS line is in non-active state after
> spi_setup()"). And spi_set_cs will call spi->master->set_cs, and set_cs
> callback will access register. Without clk enable, I believe some
> drivers will failed to run.

That's definitely very driver specific, a large proportion of devices
don't manage their chip selects via the SPI controller at all.

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