From mboxrd@z Thu Jan  1 00:00:00 1970
From: mturquette@baylibre.com (Michael Turquette)
Date: Mon, 11 Jul 2016 15:17:31 -0700
Subject: [PATCH v2 6/7] spi: s3c64xx: restore removed comments
In-Reply-To: <57837606.8050906@samsung.com>
References: <1467989201-14661-1-git-send-email-andi.shyti@samsung.com>
 <1467989201-14661-7-git-send-email-andi.shyti@samsung.com>
 <146799464881.73491.7507792367941552864@resonance>
 <57837606.8050906@samsung.com>
Message-ID: <146827545163.73491.5083923656346798965@resonance>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Quoting Sylwester Nawrocki (2016-07-11 03:33:42)
> On 07/08/2016 06:17 PM, Michael Turquette wrote:
> > Quoting Andi Shyti (2016-07-08 07:46:40)
> 
> >> 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