On Sunday, October 02, 2011, Sylwester Nawrocki wrote: > On 10/02/2011 09:07 AM, Kukjin Kim wrote: > > Rafael J. Wysocki wrote: > >> > >> On Saturday, August 13, 2011, Russell King - ARM Linux wrote: > >>> On Sat, Aug 13, 2011 at 11:24:07PM +0200, Rafael J. Wysocki wrote: > >>>> On Thursday, August 11, 2011, Chanwoo Choi wrote: > >>>>> The following patch set use the generic Power domain Framework > > instead of > >>>>> power domain code depend of Samsung SoC. > >>>>> > >>>>> Chanwoo Choi (4): > >>>>> ARM: EXYNOS4: Support for generic I/O power domains on EXYNOS4210 > >>>>> ARM: EXYNOS4: Support for generic Clock manipulation PM callbacks > >>>>> ARM: EXYNOS4: Delete the power-domain code depend on Samsung SoC > >>>>> ARM: EXYNOS4: Add power domain to use generic Power domain > > Framework > >>>>> > >>>>> arch/arm/mach-exynos4/Kconfig | 10 +- > >>>>> arch/arm/mach-exynos4/Makefile | 4 +- > >>>>> arch/arm/mach-exynos4/dev-pd.c | 139 > > -------------- > >>>>> arch/arm/mach-exynos4/include/mach/pm-exynos4210.h | 52 ++++++ > >>>>> arch/arm/mach-exynos4/include/mach/regs-clock.h | 8 + > >>>>> arch/arm/mach-exynos4/mach-nuri.c | 21 ++- > >>>>> arch/arm/mach-exynos4/mach-smdkc210.c | 26 ++- > >>>>> arch/arm/mach-exynos4/mach-smdkv310.c | 23 ++- > >>>>> arch/arm/mach-exynos4/mach-universal_c210.c | 21 ++- > >>>>> arch/arm/mach-exynos4/pm-exynos4210.c | 189 > > ++++++++++++++++++++ > >>>>> arch/arm/mach-exynos4/pm-runtime.c | 56 ++++++ > >>>>> arch/arm/plat-samsung/Kconfig | 8 - > >>>>> arch/arm/plat-samsung/Makefile | 4 - > >>>>> arch/arm/plat-samsung/include/plat/pd.h | 30 --- > >>>>> arch/arm/plat-samsung/pd.c | 95 > > ---------- > >>>>> 15 files changed, 377 insertions(+), 309 deletions(-) > >>>>> delete mode 100644 arch/arm/mach-exynos4/dev-pd.c > >>>>> create mode 100644 > > arch/arm/mach-exynos4/include/mach/pm-exynos4210.h > >>>>> create mode 100644 arch/arm/mach-exynos4/pm-exynos4210.c > >>>>> create mode 100644 arch/arm/mach-exynos4/pm-runtime.c > >>>>> delete mode 100644 arch/arm/plat-samsung/include/plat/pd.h > >>>>> delete mode 100644 arch/arm/plat-samsung/pd.c > >>>> > >>>> The patchset looks good to me, but please note that some code it > >>>> is based on will most likely change in 3.2 due to this patchset: > >>>> > >>>> https://lkml.org/lkml/2011/8/8/420 > >>> > >>> Err, isn't all that pm_clk stuff just duplicating what the clk API does? > >> > >> I'm not sure it's duplicating anything. Maybe it does, but it came into > >> being by moving some code that were duplicated in a few places throughout > >> the ARM and sh trees into one place. > >> > >>> IOW, drivers _can_ (and should be) calling clk_disable() when they don't > >>> need the clock running. > >> > >> Drivers may not know about what to do in a given situation. For example, > >> if the system has power domains, it may be better to switch a power domain > >> off instead of or in addition to disabling the clock and the driver > > usually > >> doesn't know about that. > >> > > Hmm... Even though each driver cannot know the given situation, the driver > > can know each own clock should be alive or not. I think, if clock gating > > (enable, disable clock) is required, it should be handled in each driver. In > > addition, the clock and power are not always one-on-one match. > > AFAICS the genpd API doesn't for an architecture to move the clocks' control > out from drivers, it can be decided on individual basis for each clock. That's correct. > With Chanwoo's patches at least exynos power domains and global clock gates > for devices (S5P_CLKGATE_BLOCK) are handled through the common API. > > Also, it's not quite clear to me, can't the pm_clk_* calls be used by the drivers > to control the clocks as they need ? Well, the idea is to use them as a driver's or subsystem's .runtime_suspend() and .runtime_resume() callbacks, or a PM domain's .stop_device() and .start_device() callbacks, but I don't see fundamental arguments against calling them directly. > Last time I looked at the genpd API, an important drawback was that pm_clk_suspend/ > pm_clk_resume couldn't be used in interrupt context. Now it seems the mutexes in > the core functions has been replaced with spinlocks and such limitation is gone. Yes, it is gone now. > I'm considering using pm_clk* calls to implement clock gating in a video codec > driver. If, for instance, frame period is 30 ms and processing in the device takes > only 10 ms, significant power savings could be achieved by turning the clocks off > for the 20 ms idle period. That sounds like a good idea. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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