Hi Chris,
On Fri, Aug 5, 2016 at 3:36 PM, Chris Brandt <chris.brandt@xxxxxxxxxxx> wrote:
> When you leave the clock divider at 0, 130kHz is the lowest you can go.
> Also, by adjusting the clock divider you can get more accurate resolutions
> for clock speeds lower than 16MHz. This patch uses the clock divider as
> part of the bit rate setup.
>
> Signed-off-by: Chris Brandt <chris.brandt@xxxxxxxxxxx>
> ---
> drivers/spi/spi-rspi.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c
> index 8188433..a816f07 100644
> --- a/drivers/spi/spi-rspi.c
> +++ b/drivers/spi/spi-rspi.c
> @@ -295,14 +295,24 @@ static int rspi_set_config_register(struct rspi_data *rspi, int access_size)
> static int rspi_rz_set_config_register(struct rspi_data *rspi, int access_size)
> {
> int spbr;
> + int div = 0;
> + unsigned long clksrc;
>
> /* Sets output mode, MOSI signal, and (optionally) loopback */
> rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR);
>
> + clksrc = clk_get_rate(rspi->clk);
> + while (div < 3) {
> + if (rspi->max_speed_hz >= clksrc/4) /* 4=(CLK/2)/2 */
> + break;
> + div++;
> + clksrc /= 2;
> + }
> +
> /* Sets transfer bit rate */
> - spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk),
> - 2 * rspi->max_speed_hz) - 1;
> + spbr = DIV_ROUND_UP(clksrc, 2 * rspi->max_speed_hz) - 1;
> rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
> + rspi->spcmd |= div << 2;
>
> /* Disable dummy transmission, set byte access */
> rspi_write8(rspi, SPDCR_SPLBYTE, RSPI_SPDCR);
I believe this applies not only to RZ, but to all other supported RSPI variants?
Hence I think it should be made common.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
