[GIT PULL] Renesas ARM-based SoC: r8a7740 SoC for 3.7

Hi Olof, Hi Arnd,

please consider the following documentation enhancement for the
r8a7740 SoC from Morimoto-san for inclusion in 3.7.

----------------------------------------------------------------
The following changes since commit fea7a08acb13524b47711625eebea40a0ede69a0:

  Linux 3.6-rc3 (2012-08-22 13:29:06 -0700)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/horms/renesas.git r8a7740

for you to fetch changes up to a6e7c110f972d7ca5c6eb288f5e64d5659b44dc0:

  ARM: shmobile: r8a7740: add USB24 clock explain and sample code (2012-08-27 17:43:22 +0900)

----------------------------------------------------------------
Kuninori Morimoto (1):
      ARM: shmobile: r8a7740: add USB24 clock explain and sample code

 arch/arm/mach-shmobile/clock-r8a7740.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

From: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>

USBCKCR is controlling USB parent clock and divide rate.
This parent clock is used as a "usb24s" from other devices,
but the "divide rate" is not used.
Further, this clock itself is known as "usb24".
So, to set this clock is a little confusable.
This patch adds quick explain and sample code for this clock.

Cc: Damian Hobson-Garcia <redacted>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
---
 arch/arm/mach-shmobile/clock-r8a7740.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm/mach-shmobile/clock-r8a7740.c b/arch/arm/mach-shmobile/clock-r8a7740.c
index ad5fccc..a6a7583 100644
--- a/arch/arm/mach-shmobile/clock-r8a7740.c
+++ b/arch/arm/mach-shmobile/clock-r8a7740.c

@@ -188,6 +188,22 @@ static struct clk pllc1_div2_clk = {
 };
 
 /* USB clock */
+/*
+ * USBCKCR is controlling usb24 clock
+ * bit[7] : parent clock
+ * bit[6] : clock divide rate
+ * And this bit[7] is used as a "usb24s" from other devices.
+ * (Video clock / Sub clock / SPU clock)
+ * You can controll this clock as a below.
+ *
+ * struct clk *usb24	= clk_get(dev,  "usb24");
+ * struct clk *usb24s	= clk_get(NULL, "usb24s");
+ * struct clk *system	= clk_get(NULL, "system_clk");
+ * int rate = clk_get_rate(system);
+ *
+ * clk_set_parent(usb24s, system);  // for bit[7]
+ * clk_set_rate(usb24, rate / 2);   // for bit[6]
+ */
 static struct clk *usb24s_parents[] = {
 	[0] = &system_clk,
 	[1] = &extal2_clk

-- 
1.7.10.2.484.gcd07cc5

Hi,

A couple of comments below.

On Thu, Aug 30, 2012 at 02:52:49PM +0900, Simon Horman wrote:

The divisor is either 1 or 2 in this case, for bit[6] values of 0 and 1?

+ * And this bit[7] is used as a "usb24s" from other devices.

Sorry, I don't follow the explanation here.

This is how I interpret the current code, can you confirm if it's accurate?

usb24 is the (potentially) divided output from usb24s, while usb24s is
at a fixed pass-through rate from the parent if enabled. Both share the
same enable bit. In other words, usb24 is a directly derived, potentially
divided-by-two rate from usb24s?

This is just standard clk infrastructure usage, I don't think there's need to
include the example code here.


-Olof

Hi Olof

Thank you for checking patch

On Thu, Aug 30, 2012 at 02:52:49PM +0900, Simon Horman wrote:

quoted

From: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>

USBCKCR is controlling USB parent clock and divide rate.
This parent clock is used as a "usb24s" from other devices,
but the "divide rate" is not used.
Further, this clock itself is known as "usb24".
So, to set this clock is a little confusable.
This patch adds quick explain and sample code for this clock.

Cc: Damian Hobson-Garcia <redacted>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
---
 arch/arm/mach-shmobile/clock-r8a7740.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/arm/mach-shmobile/clock-r8a7740.c b/arch/arm/mach-shmobile/clock-r8a7740.c
index ad5fccc..a6a7583 100644
--- a/arch/arm/mach-shmobile/clock-r8a7740.c
+++ b/arch/arm/mach-shmobile/clock-r8a7740.c

@@ -188,6 +188,22 @@ static struct clk pllc1_div2_clk = {
 };
 
 /* USB clock */
+/*
+ * USBCKCR is controlling usb24 clock
+ * bit[7] : parent clock
+ * bit[6] : clock divide rate

The divisor is either 1 or 2 in this case, for bit[6] values of 0 and 1?

Yes.
if (0 = bit[6]) clock is 1/2
if (1 = bit[6]) clock is 1/1

quoted

+ * And this bit[7] is used as a "usb24s" from other devices.

Sorry, I don't follow the explanation here.

This is how I interpret the current code, can you confirm if it's accurate?

usb24 is the (potentially) divided output from usb24s, while usb24s is
at a fixed pass-through rate from the parent if enabled. Both share the
same enable bit. In other words, usb24 is a directly derived, potentially
divided-by-two rate from usb24s?

clcok A ---+  bit[7]                 bit[6]
           |- select -> usb24s -+--> divide (1/1 or 1/2) -> usb24
clock B ---+                    |
                                +--> other clocks ->

quoted

+ * (Video clock / Sub clock / SPU clock)
+ * You can controll this clock as a below.
+ *
+ * struct clk *usb24	= clk_get(dev,  "usb24");
+ * struct clk *usb24s	= clk_get(NULL, "usb24s");
+ * struct clk *system	= clk_get(NULL, "system_clk");
+ * int rate = clk_get_rate(system);
+ *
+ * clk_set_parent(usb24s, system);  // for bit[7]
+ * clk_set_rate(usb24, rate / 2);   // for bit[6]

This is just standard clk infrastructure usage, I don't think there's need to
include the example code here.

Ahh.. 50% yes.

_If_ this usb24/usb24s explanation on datasheet is same as other clocks,
it is easy to understand and can use clk_set_rate().

But this setting style of these 2 clock is very special case on our datasheet.
Maybe first case.
So, I added sample setting code here,
since it is difficult to understand how to set the clock from
datasheet/clock tree and clock-r8a7740.c

Best regards
---
Kuninori Morimoto