Linux-Clk Archive on lore.kernel.org
 help / color / Atom feed
From: Michael Turquette <mturquette@baylibre.com>
To: Sylwester Nawrocki <s.nawrocki@samsung.com>,
	"Andi Shyti" <andi.shyti@samsung.com>
Cc: "Rob Herring" <robh+dt@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Kukjin Kim" <kgene@kernel.org>,
	"Krzysztof Kozlowski" <k.kozlowski@samsung.com>,
	"Mark Brown" <broonie@kernel.org>,
	"Tomasz Figa" <tomasz.figa@gmail.com>,
	"Stephen Boyd" <sboyd@codeaurora.org>,
	"Chanwoo Choi" <cw00.choi@samsung.com>,
	"Jaehoon Chung" <jh80.chung@samsung.com>,
	linux-clk@vger.kernel.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-spi@vger.kernel.org,
	"Andi Shyti" <andi@etezian.org>
Subject: Re: [PATCH v2 6/7] spi: s3c64xx: restore removed comments
Date: Mon, 11 Jul 2016 15:17:31 -0700
Message-ID: <146827545163.73491.5083923656346798965@resonance> (raw)
In-Reply-To: <57837606.8050906@samsung.com>

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

  reply index

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-08 14:46 [PATCH v2 0/7] spi s3c64xx ioclk handling Andi Shyti
2016-07-08 14:46 ` [PATCH v2 1/7] bindings: spi-samsung: add exynos5433 spi compatible Andi Shyti
2016-07-08 20:23   ` Krzysztof Kozlowski
2016-07-11 10:49   ` Sylwester Nawrocki
2016-07-14 16:33   ` Applied "spi: s3c64xx: add exynos5433 spi compatible" to the spi tree Mark Brown
2016-07-08 14:46 ` [PATCH v2 2/7] bindings: spi-samsung: document the clocks and the clock-name property Andi Shyti
2016-07-08 14:46 ` [PATCH v2 3/7] spi: s3c64xx: rename goto labels to meaningful names Andi Shyti
2016-07-14 16:32   ` Applied "spi: s3c64xx: rename goto labels to meaningful names" to the spi tree Mark Brown
2016-07-08 14:46 ` [PATCH v2 4/7] spi: s3c64xx: use error code from clk_prepare_enable() Andi Shyti
2016-07-08 20:33   ` Krzysztof Kozlowski
2016-07-14 16:32   ` Applied "spi: s3c64xx: use error code from clk_prepare_enable()" to the spi tree Mark Brown
2016-07-08 14:46 ` [PATCH v2 5/7] spi: s3c64xx: add exynos5433 compatible for ioclk handling Andi Shyti
2016-07-08 16:13   ` Michael Turquette
2016-07-08 16:31     ` Andi Shyti
2016-07-08 20:39   ` Krzysztof Kozlowski
2016-07-14 16:32   ` Applied "spi: s3c64xx: add Exynos5433 compatible for ioclk handling" to the spi tree Mark Brown
2016-07-08 14:46 ` [PATCH v2 6/7] spi: s3c64xx: restore removed comments Andi Shyti
2016-07-08 16:17   ` Michael Turquette
2016-07-08 16:35     ` Andi Shyti
2016-07-11 10:33     ` Sylwester Nawrocki
2016-07-11 22:17       ` Michael Turquette [this message]
2016-07-12 12:16         ` Sylwester Nawrocki
2016-07-12  6:54       ` [PATCH v3 " Andi Shyti
2016-07-12  8:22         ` Mark Brown
2016-07-12  8:25           ` Andi Shyti
2016-07-12  9:00             ` Mark Brown
2016-07-12 18:07         ` Michael Turquette
2016-07-14 16:32         ` Applied "spi: s3c64xx: restore removed comments" to the spi tree Mark Brown
2016-07-08 20:35   ` [PATCH v2 6/7] spi: s3c64xx: restore removed comments Krzysztof Kozlowski
2016-07-08 14:46 ` [PATCH v2 7/7] clk: exynos5433: remove CLK_IGNORE_UNUSED flag from SPI clocks Andi Shyti
2016-07-11 10:58   ` Sylwester Nawrocki
2016-07-08 16:21 ` [PATCH v2 0/7] spi s3c64xx ioclk handling Michael Turquette
2016-07-11  2:36 [PATCH v3] bindings: spi-samsung: document the clocks and the clock-name property Andi Shyti
2016-07-14 16:32 ` Applied "spi: s3c64xx: document the clocks and the clock-name property" to the spi tree Mark Brown

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=146827545163.73491.5083923656346798965@resonance \
    --to=mturquette@baylibre.com \
    --cc=andi.shyti@samsung.com \
    --cc=andi@etezian.org \
    --cc=broonie@kernel.org \
    --cc=cw00.choi@samsung.com \
    --cc=devicetree@vger.kernel.org \
    --cc=jh80.chung@samsung.com \
    --cc=k.kozlowski@samsung.com \
    --cc=kgene@kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-clk@vger.kernel.org \
    --cc=linux-samsung-soc@vger.kernel.org \
    --cc=linux-spi@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=robh+dt@kernel.org \
    --cc=s.nawrocki@samsung.com \
    --cc=sboyd@codeaurora.org \
    --cc=tomasz.figa@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Clk Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-clk/0 linux-clk/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-clk linux-clk/ https://lore.kernel.org/linux-clk \
		linux-clk@vger.kernel.org
	public-inbox-index linux-clk

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-clk


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git