On Fri, Nov 25, 2016 at 8:08 PM, Phil Edworthy <phil.edwor...@renesas.com> wrote: > With the existing code, when the requested SPI clock rate is near > to the lowest that can be achieved by the hardware (max divider > of the ref clock is 32), the generated clock rate is wrong. > For example, with a 50MHz ref clock, when asked for anything less > than a 1.5MHz SPI clock, the code sets up the divider to generate > 25MHz. > > This change fixes the calculation. > > Signed-off-by: Phil Edworthy <phil.edwor...@renesas.com> > --- > v2: > - Use the DIV_ROUND_UP macro > --- > drivers/spi/cadence_qspi_apb.c | 23 +++++++---------------- > 1 file changed, 7 insertions(+), 16 deletions(-) > > diff --git a/drivers/spi/cadence_qspi_apb.c b/drivers/spi/cadence_qspi_apb.c > index 2403e71..b9e0df7 100644 > --- a/drivers/spi/cadence_qspi_apb.c > +++ b/drivers/spi/cadence_qspi_apb.c > @@ -273,22 +273,13 @@ void cadence_qspi_apb_config_baudrate_div(void > *reg_base, > reg = readl(reg_base + CQSPI_REG_CONFIG); > reg &= ~(CQSPI_REG_CONFIG_BAUD_MASK << CQSPI_REG_CONFIG_BAUD_LSB); > > - div = ref_clk_hz / sclk_hz; > - > - if (div > 32) > - div = 32; > - > - /* Check if even number. */ > - if ((div & 1)) { > - div = (div / 2); > - } else { > - if (ref_clk_hz % sclk_hz) > - /* ensure generated SCLK doesn't exceed user > - specified sclk_hz */ > - div = (div / 2); > - else > - div = (div / 2) - 1; > - } > + /* > + * The baud_div field in the config reg is 4 bits, and the ref clock > is > + * divided by 2 * (baud_div + 1). Round up the divider to ensure the > + * SPI clock rate is less than or equal to the requested clock rate. > + */ > + div = DIV_ROUND_UP(ref_clk_hz, sclk_hz); > + div = DIV_ROUND_UP(div, 2) - 1;
What about div = (ref / (sclk * 2)) -1 that means div = DIV_ROUND_UP(ref_clk_hz, sclk_hz * 2) -1; thanks! -- Jagan Teki Free Software Engineer | www.openedev.com U-Boot, Linux | Upstream Maintainer Hyderabad, India. _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot