linux-kernel - Re: [PATCH v3 01/13] spi: sunxi: set maximum and minimum speed of SPI master

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Date:	Mon, 13 Jun 2016 21:55:02 +0200
From:	Maxime Ripard <maxime.ripard@...e-electrons.com>
To:	Michal Suchanek <hramrach@...il.com>
Cc:	linux-sunxi@...glegroups.com, stable@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Chen-Yu Tsai <wens@...e.org>,
	Russell King <linux@...linux.org.uk>,
	Mark Brown <broonie@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	Olof Johansson <olof@...om.net>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Simon Horman <horms+renesas@...ge.net.au>,
	Sjoerd Simons <sjoerd.simons@...labora.co.uk>,
	Thierry Reding <treding@...dia.com>,
	Alison Wang <b18965@...escale.com>,
	Timo Sigurdsson <public_timo.s@...entcreek.de>,
	Jonathan Liu <net147@...il.com>,
	Gerhard Bertelsmann <info@...hard-bertelsmann.de>,
	Priit Laes <plaes@...es.org>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-spi@...r.kernel.org
Subject: Re: [PATCH v3 01/13] spi: sunxi: set maximum and minimum speed of
 SPI master

On Mon, Jun 13, 2016 at 05:46:49PM -0000, Michal Suchanek wrote:
> The speed limits are unset in the sun4i and sun6i SPI drivers.
> 
> The maximum speed of SPI master is used when maximum speed of SPI slave
> is not specified. Also the __spi_validate function should check that
> transfer speeds do not exceed the master limits.
> 
> The user manual for A10 and A31 specifies maximum
> speed of the SPI clock as 100MHz and minimum as 3kHz.
> 
> Setting the SPI clock to out-of-spec values can lock up the SoC.
> 
> Signed-off-by: Michal Suchanek <hramrach@...il.com>
> --
> v2:
> new patch
> v3:
> fix constant style
> ---
>  drivers/spi/spi-sun4i.c | 2 ++
>  drivers/spi/spi-sun6i.c | 2 ++
>  2 files changed, 4 insertions(+)
> 
> diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c
> index 1ddd9e2..4213508 100644
> --- a/drivers/spi/spi-sun4i.c
> +++ b/drivers/spi/spi-sun4i.c
> @@ -387,6 +387,8 @@ static int sun4i_spi_probe(struct platform_device *pdev)
>  	}
>  
>  	sspi->master = master;
> +	master->max_speed_hz = 100 * 1000 * 1000;
> +	master->min_speed_hz =          3 * 1000;
>  	master->set_cs = sun4i_spi_set_cs;
>  	master->transfer_one = sun4i_spi_transfer_one;
>  	master->num_chipselect = 4;
> diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
> index 42e2c4b..fe70695 100644
> --- a/drivers/spi/spi-sun6i.c
> +++ b/drivers/spi/spi-sun6i.c
> @@ -386,6 +386,8 @@ static int sun6i_spi_probe(struct platform_device *pdev)
>  	}
>  
>  	sspi->master = master;
> +	master->max_speed_hz = 100 * 1000 * 1000;
> +	master->min_speed_hz =          3 * 1000;
>  	master->set_cs = sun6i_spi_set_cs;
>  	master->transfer_one = sun6i_spi_transfer_one;
>  	master->num_chipselect = 4;

I really don't get why you want to do that kind of padding, when no
one does in the rest of the driver, or the rest of the kernel.

Once properly changed,
Acked-by: Maxime Ripard <maxime.ripard@...e-electrons.com>

Thanks,
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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