[PATCH linux dev-4.13 5/6] fsi/fsi-master-gpio: Reduce turnaround clocks

[Christopher Bostic]

Reviewed-by: Christopher Bostic <cbostic at linux.vnet.ibm.com>


On 5/7/18 8:06 PM, Benjamin Herrenschmidt wrote:
> FSI_GPIO_PRIME_SLAVE_CLOCKS is the number of clocks if the
> "idle" phase between the end of a response and the beginning
> of the next one. It corresponds to tSendDelay in the FSI
> specification.
>
> The default value in the slave is 16 clocks. 100 is way overkill
> and significantly reduces the driver performance.
>
> This changes it to 20 (which gives the HW a bit of margin still
> just in case).
>
> Signed-off-by: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> ---
>   drivers/fsi/fsi-master-gpio.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/fsi/fsi-master-gpio.c b/drivers/fsi/fsi-master-gpio.c
> index c82bbd35276e..029b0a5b6d89 100644
> --- a/drivers/fsi/fsi-master-gpio.c
> +++ b/drivers/fsi/fsi-master-gpio.c
> @@ -49,7 +49,7 @@
>   #define	FSI_GPIO_CRC_SIZE	4
>   #define	FSI_GPIO_MSG_ID_SIZE		2
>   #define	FSI_GPIO_MSG_RESPID_SIZE	2
> -#define	FSI_GPIO_PRIME_SLAVE_CLOCKS	100
> +#define	FSI_GPIO_PRIME_SLAVE_CLOCKS	20
>
>   struct fsi_master_gpio {
>   	struct fsi_master	master;