[PATCH v2 0/6] ARM: S5PV210: Add support S5PV210/S5PC110 CPUFREQ

[MyungJoo Ham]

On Mon, Oct 11, 2010 at 5:04 PM, Sangbeom Kim <sbkim73 at samsung.com> wrote:
> On Monday, Oct 11, 2010 9:12 AM, MyungJoo Ham <myungjoo.ham at samsung.com> wrote:
>>
>> Hello,
>>
>> On Fri, Oct 8, 2010 at 6:52 PM, Kukjin Kim <kgene.kim at samsung.com> wrote:
>> > Sangbeom Kim wrote:
>> >>
>> >> Hi all,
>> >> I know that there is another S5PV210 CPUFREQ patch from Mr. Ham.
>> >> But, That patchset seems to have unclear part.
>> >>
>> > http://lists.infradead.org/pipermail/linux-arm-kernel/2010-
>> August/023626.htm
>> >> l
>> >> The part of 'CONFIG_PM' is unclear and still have PM support part.
>> >> So, I think that this patch is more suitable for S5PV210/S5PC110
>> CPUFREQ
>> > in
>> >> the mainline.
>> >> because this patch implemented basic pm functionality and already
>> tested
>> > on
>> >> smdkv210 board.
>> >>
>> > Hi,
>> >
>> > So...I'd like to merge this for this merge window.
>> >
>> > Mr. Ham, how do you think?
>> > If any problems or opinions, please let me know.
>>
>>
>> You can go ahead as long as this patch include features that the
>> another addresses.
>>
>>
>> Anyway, the part that is under "CONFIG_PM" is intended to block
>> frequency changing while PM is doing something. For example, when the
>> system enters a sleep, if CPUFREQ somehow enters "100MHz/0.95V" just
>> before the sleep and wakes up, the voltage may stay at 0.95V (PMIC is
>> not turned off during sleep) while the frequency is reset to 800MHz
>> (by the bootloader), which requires, let's say, 1.1V. Such
>> inconsistency may lead to system hang and we have observed such cases
>> a few times. I intended to refuse any CPUFREQ requests at the
>> /mach-s5pv210/cpufreq.c when PM seems to start.
>>
>
> We knew already that issue,
> So we have a plan to implement with other solution.
> (using regulator suspend feature)
>
>> It may seem that such feature is not needed if the voltage is not
>> optimized, however, CPUFREQ is useless if the voltage stays at 1.2V
>> and if the voltage changes properly according to the frequency, such
>> feature is required anyway.
>
> Currently, there is no max8698 regulator driver on mainline.
> After submission that driver, we can add voltage scaling feature.
>
> Both issues have dependency on regulator driver.

Nope. it does not need to depend on any regulator drivers. We can
simply stop changing frequency (or hold at a specific frequency) after
suspend-to-mem is called. (probably at ".begin" stage). This depends
on PM, but does NOT depend on REGULATOR.

The approach in the removed patch was to set a flag at the .begin PM
ops and deflag it at .end PM ops and let target function of CPUFREQ to
read the flag to decide whether to accept the frequency change request
and to set at the default frequency (i.e., 800MHz) when .begin ops is
called and restore the frequency when .end ops is called.


>
>>
>>
>> ps. Anyway, such feature is also not included in my patch, either. :(
>> (tried to included, but the code was excluded at the patch patching
>> the patch.)
>>
>> >
>> > Thanks.
>> >
>> > Best regards,
>> > Kgene.
>> > --
>> > Kukjin Kim <kgene.kim at samsung.com>, Senior Engineer,
>> > SW Solution Development Team, Samsung Electronics Co., Ltd.
>> >
>> >> Thanks and regards,
>> >> S.B. Kim
>> >>
>> >> > on Monday, September 20, 2010 3:05 PM, Sangbeom Kim
>> >> <sbkim73 at samsung.com>
>> >> wrote:
>> >> >
>> >> > This patch adds CPUFREQ for S5PV210/S5PC110.
>> >> >
>> >> > Changes since v1:
>> >> >
>> >> > - Added MOUT_DMC0 and SCLK_DMC0 for checking the dmc0 clock in
>> >> CPUFREQ
>> >> > driver.
>> >> > - Removed hardcoding of DRAM refresh counter.
>> >> > - Added to calculate refresh counter function based on DRAM operation
>> >> freq.
>> >> >
>> >> > [PATCH v2 1/6] ARM: S5PV210: Add DMC map_desc table for supporting
>> DMC
>> >> > access
>> >> > [PATCH v2 2/6] ARM: S5PV210: Add struct clk_ops for clk_fout_apll
>> >> > [PATCH v2 3/6] ARM: S5PV210: Add MOUT_DMC0 and SCLK_DMC0 clocks
>> >> > [PATCH v2 4/6] ARM: S5PV210: Add Register definition for CMU
>> >> > [PATCH v2 5/6] ARM: S5PV210: Add support CPUFREQ
>> >> > [PATCH v2 6/6] ARM: S5PV210: Update Kconfig and Makefile for
>> supporting
>> >> > CPUFREQ driver
>> >> > --
>> >> > To unsubscribe from this list: send the line "unsubscribe linux-
>> samsung-
>> >> > soc" in
>> >> > the body of a message to majordomo at vger.kernel.org
>> >> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> >
>> >
>> > _______________________________________________
>> > linux-arm-kernel mailing list
>> > linux-arm-kernel at lists.infradead.org
>> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>> >
>>
>>
>>
>> --
>> MyungJoo Ham (함명주), Ph.D.
>> Mobile Software Platform Lab,
>> Digital Media and Communications (DMC) Business
>> Samsung Electronics
>> cell: 82-10-6714-2858
>>
>> _______________________________________________
>> linux-arm-kernel mailing list
>> linux-arm-kernel at lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>



-- 
MyungJoo Ham (함명주), Ph.D.
Mobile Software Platform Lab,
Digital Media and Communications (DMC) Business
Samsung Electronics
cell: 82-10-6714-2858