Quoting Sylwester Nawrocki (2016-07-11 03:33:42)

On 07/08/2016 06:17 PM, Michael Turquette wrote:

quoted

Quoting Andi Shyti (2016-07-08 07:46:40)

quoted

quoted

diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index 6da663f..32b66f0 100644
--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c

@@ -639,6 +639,7 @@ static void s3c64xx_spi_config(struct s3c64xx_spi_driver_data *sdd)
        writel(val, regs + S3C64XX_SPI_MODE_CFG);
 
        if (sdd->port_conf->clk_from_cmu) {
+               /* There is half-multiplier before the SPI */
                clk_set_rate(sdd->src_clk, sdd->cur_speed * 2);

Just a small comment, but if the fixed-factor divide-by-two clock was
modeled in Linux, then this driver could call clk_set_rate on that clock
with the "correct" rate.

I guess that this driver would be the provider of that clock?

Good point, however I'm not sure if it is worth to model this divider
with a clk object.  It is an internal divider and the clock it provides
is only used internally within the SPI controller.  Thus the spi-s3c64xx
driver would be provider on the only consumer of this clock.

Sure, but it's only a few lines of code to this, and there are examples
in the kernel already.

Additionally, the "There is half-multiplier before the SPI" comment
seems to be obfuscating how the hardware really looks like to me.
It talks about multiplier (which reminds me of PLLs with a divider
in the feedback loop) while there is a simple divider which should
be considered as an integral part of the controller IP block.

While we are at it, I'd propose to change this comment to something
like:

/* The SCLK_SPI clock is divided internally by 2 */

It's your choice, but debug output would benefit from showing the real
clock frequency at some point.

Regards,
Mike