Re: [PATCH 2/2] spi: bcm2835: Allow platform to set realtime priority

[Alexander Stein <alexanders83@xxxxxx>]

Hi,

interesting, but why is this property specific to bcm2835 when the priority is 
used in generic code only?

Best regards,
Alexander

On Thursday 23 March 2017 11:36:45, Lukas Wunner wrote:
> Revolution Pi (a set of IoT products based on the Raspberry Pi and
> geared towards industrial usage) uses the bcm2835's SPI master to
> interface with an IEC 61158 fieldbus, which requires its kworker thread
> to run at a realtime priority.  To this end, allow the platform to
> specify the desired priority.
> 
> Cc: Mark Brown <broonie@xxxxxxxxxx>
> Cc: Stephen Warren <swarren@xxxxxxxxxxxxx>
> Cc: Eric Anholt <eric@xxxxxxxxxx>
> Cc: Mathias Duckeck <m.duckeck@xxxxxxxxx>
> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
> ---
>  Documentation/devicetree/bindings/spi/brcm,bcm2835-spi.txt | 4 ++++
>  drivers/spi/spi-bcm2835.c                                  | 2 ++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/spi/brcm,bcm2835-spi.txt
> b/Documentation/devicetree/bindings/spi/brcm,bcm2835-spi.txt index
> f11f295c8450..13ffc2b15e7d 100644
> --- a/Documentation/devicetree/bindings/spi/brcm,bcm2835-spi.txt
> +++ b/Documentation/devicetree/bindings/spi/brcm,bcm2835-spi.txt
> @@ -10,6 +10,10 @@ Required properties:
>  - interrupts: Should contain interrupt.
>  - clocks: The clock feeding the SPI controller.
> 
> +Optional properties:
> +- bcm2835,rt_prio: Realtime priority of the message pump to minimize
> latency +                   on the bus (0..99).
> +
>  Example:
> 
>  spi@20204000 {
> diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
> index f35cc10772f6..319523686f73 100644
> --- a/drivers/spi/spi-bcm2835.c
> +++ b/drivers/spi/spi-bcm2835.c
> @@ -755,6 +755,8 @@ static int bcm2835_spi_probe(struct platform_device
> *pdev) master->handle_err = bcm2835_spi_handle_err;
>  	master->prepare_message = bcm2835_spi_prepare_message;
>  	master->dev.of_node = pdev->dev.of_node;
> +	of_property_read_u32(pdev->dev.of_node,
> +			     "bcm2835,rt_prio", &master->rt_prio);
> 
>  	bs = spi_master_get_devdata(master);

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