On 02/16/12 19:42, Heiko Stübner wrote:
The S3C2416/S3C2450 SoCs support two sources for the armclk.
The first source is the so called armdiv which divides the msysclk down
to provide necessary cpu rates. In this mode the core voltage must be
always at 1.3V. The frequency from the armdiv is not allowed to be
lower than the hclk frequency.
In the second mode the armclk can be sourced directly from the hclk in
the so called "dynamic voltags scaling" (dvs) mode. Here the armdiv
isn't used at all. Also in this mode the core voltage may be lowered.
Existing hardware and tests with it suggest 1.0V as sufficient.
When changing the clock source to the armdiv from the hclk, the SoC
shows stability issues if the new frequency is higher than the current
hclk frequency. Hence the driver always forces the armdiv to the hclk
frequency before the source change and lets the cpufreq issue another
set_target call for higher frequencies.
To mark the hclk frequency as lower as the corresponding armdiv
frequency it is set 1MHz below the real frequency. This lets the cpufreq
framework change between 133MHz based on hclk and 133MHz based on armdiv
at will.
Signed-off-by: Heiko Stuebner<heiko@xxxxxxxxx>
Tested-by: Andrey Gusakov<dron0gus@xxxxxxxxx>
---
changes since v1: correct the frequencies of the S3C2450 variant
changes since RFC: reboot-notifier to leave dvs mode on reboot
and a lot of cleanups
drivers/cpufreq/Kconfig.arm | 22 ++
drivers/cpufreq/Makefile | 1 +
drivers/cpufreq/s3c2416-cpufreq.c | 542 +++++++++++++++++++++++++++++++++++++
3 files changed, 565 insertions(+), 0 deletions(-)
create mode 100644 drivers/cpufreq/s3c2416-cpufreq.c
Hi Heiko,
As you know, I'm working on move cpufreq drivers of s3c2410, s3c2412 and
s3c2440 into drivers/cpufreq/.
Now I'm not sure some common function can be used for them and this as
well. But I think, if so, would be better to us.
So please wait for some time to finish my working. Maybe next week?
Then, let me back on this.
Thanks.
Best regards,
Kgene.
--
Kukjin Kim <kgene.kim@xxxxxxxxxxx>, Senior Engineer,
SW Solution Development Team, Samsung Electronics Co., Ltd.
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