[PATCH linux dev-5.7 2/6] spi: fsi: Fix clock running too fast

[Joel Stanley]

On Wed, 29 Jul 2020 at 20:45, Eddie James <eajames at linux.ibm.com> wrote:
>
> From: Brad Bishop <bradleyb at fuzziesquirrel.com>
>
> Use a clock divider tuned to a 200MHz FSI clock.  Use of the previous
> divider at 200MHz results in corrupt data from endpoint devices. Ideally
> the clock divider would be calculated from the FSI clock, but that
> would require some significant work on the FSI driver.

This sounds like something we should fix, especially if we're
experimenting between 200/166/100 MHz FSI clocks?

>
> Signed-off-by: Eddie James <eajames at linux.ibm.com>
> Signed-off-by: Brad Bishop <bradleyb at fuzziesquirrel.com>
> ---
>  drivers/spi/spi-fsi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi-fsi.c b/drivers/spi/spi-fsi.c
> index 8f64af0140e0..559d0ff981f3 100644
> --- a/drivers/spi/spi-fsi.c
> +++ b/drivers/spi/spi-fsi.c
> @@ -350,7 +350,7 @@ static int fsi_spi_transfer_init(struct fsi_spi *ctx)
>         u64 status = 0ULL;
>         u64 wanted_clock_cfg = SPI_FSI_CLOCK_CFG_ECC_DISABLE |
>                 SPI_FSI_CLOCK_CFG_SCK_NO_DEL |
> -               FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, 4);
> +               FIELD_PREP(SPI_FSI_CLOCK_CFG_SCK_DIV, 19);
>
>         end = jiffies + msecs_to_jiffies(SPI_FSI_INIT_TIMEOUT_MS);
>         do {
> --
> 2.24.0
>