[U-Boot] [PATCH] dm: spi: prevent setting a speed of 0 Hz

[Vignesh R]

On Thursday 18 January 2018 01:45 PM, Simon Goldschmidt wrote:
> When the device tree is missing a correct spi slave description below
> the bus, the 'set_speed' callback can be called with 'speed' == 0 Hz.
> At least with cadence qspi, this leads to a division by zero.
> 
> Prevent this by initializing speed to 100 kHz in this case, as is
> done in 'dm_spi_claim_bus'.
> 

As per doc/device-tree-bindings/spi/spi-bus.txt,
spi-max-frequency - (required) Maximum SPI clocking speed of device in Hz

IMO, the correct fix would be to error out with proper warning, if
spi-max-frequency property is absent in DT.

> Signed-off-by: Simon Goldschmidt <sgoldschmidt at de.pepperl-fuchs.com>
> ---
> 
>  drivers/spi/spi-uclass.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/spi/spi-uclass.c b/drivers/spi/spi-uclass.c
> index e06a603ab1..41ecef77db 100644
> --- a/drivers/spi/spi-uclass.c
> +++ b/drivers/spi/spi-uclass.c
> @@ -325,6 +325,8 @@ int spi_get_bus_and_cs(int busnum, int cs, int speed, int mode,
>  	if (!speed) {
>  		speed = plat->max_hz;
>  		mode = plat->mode;
> +		if (!speed)
> +			speed = 100000;
>  	}
>  	ret = spi_set_speed_mode(bus, speed, mode);
>  	if (ret)
> 

-- 
Regards
Vignesh