在 2011-12-20 下午11:13，"Rob Herring" <robherri...@gmail.com>写道： > > On 12/19/2011 07:59 PM, Richard Zhao wrote: > > On Mon, Dec 19, 2011 at 09:00:44AM -0600, Rob Herring wrote: > >> On 12/19/2011 08:39 AM, Jamie Iles wrote: > >>> On Mon, Dec 19, 2011 at 10:19:29PM +0800, Richard Zhao wrote: > >>>> On Mon, Dec 19, 2011 at 10:05:12AM +0000, Jamie Iles wrote: > >>>>> Hi Richard, > >>>>> > >>>>> On Mon, Dec 19, 2011 at 11:21:40AM +0800, Richard Zhao wrote: > >>>>>> It support single core and multi-core ARM SoCs. But currently it assume > >>>>>> all cores share the same frequency and voltage. > >>>>>> > >>>>>> Signed-off-by: Richard Zhao <richard.z...@linaro.org> > >>>>>> --- > >>>>>> .../devicetree/bindings/cpufreq/generic-cpufreq | 7 + > >>>>>> drivers/cpufreq/Kconfig | 8 + > >>>>>> drivers/cpufreq/Makefile | 2 + > >>>>>> drivers/cpufreq/generic-cpufreq.c | 251 ++++++++++++++++++++ > >>>>>> 4 files changed, 268 insertions(+), 0 deletions(-) > >>>>>> create mode 100644 Documentation/devicetree/bindings/cpufreq/generic-cpufreq > >>>>>> create mode 100644 drivers/cpufreq/generic-cpufreq.c > >>>>>> > >>>>>> diff --git a/Documentation/devicetree/bindings/cpufreq/generic-cpufreq b/Documentation/devicetree/bindings/cpufreq/generic-cpufreq > >>>>>> new file mode 100644 > >>>>>> index 0000000..15dd780 > >>>>>> --- /dev/null > >>>>>> +++ b/Documentation/devicetree/bindings/cpufreq/generic-cpufreq > >>>>>> @@ -0,0 +1,7 @@ > >>>>>> +Generic cpufreq driver > >>>>>> + > >>>>>> +Required properties in /cpus/cpu@0: > >>>>>> +- compatible : "generic-cpufreq" > >>>>> > >>>>> I'm not convinced this is the best way to do this. By requiring a > >>>>> generic-cpufreq compatible string we're encoding Linux driver > >>>>> information into the hardware description. The only way I can see to > >>>>> avoid this is to provide a generic_clk_cpufreq_init() function that > >>>>> platforms can call in their machine init code to use the driver. > >> > >> Agreed on the compatible string. > > Assume you reject to use compatible string. > >> It's putting Linux specifics into DT. > >> > >> You could flip this around and have the module make a call into the > >> kernel to determine whether to initialize or not. Then platforms could > >> set a flag to indicate this. > > Could you make it more clear? kernel global variable, macro, or function? > > Any of those. Of course, direct access to variables across modules is > discouraged, so it would probably be a function that checks a variable. why not use function pointer? arch that don't use this driver do not have to set it. if use function, everyone should define it. > > > - Following your idea, I think, we can add in driver/cpufreq/cpufreq.c: > > int (*clk_reg_cpufreq_get_op_table) (struct op_table *tbl, int *size); > > SoC code set the callback. If it's NULL, driver will exit. We can get rid > > of DT. It'll make cpufreq core dirty, but it's the only file built-in. > > But aren't you getting the operating points from the DT? Then you don't > want to put this code into each platform. the variable is mainly used to check whether some platform want to use this driver. getting ride of dt is side affect. > > > > > - Drop module support. SoC call generic_clk_cpufreq_init as Jamie said. > > > >> > >>>> It'll prevent the driver from being a kernel module. > >>> > >>> Hmm, that's not very nice either! I guess you _could_ add an > >>> of_machine_is_compatible() check against a list of compatible machines > >>> in the driver but that feels a little gross. Hopefully Rob or Grant > >>> have a good alternative! > >>> > >> > >> What does cpufreq core do if multiple drivers are registered? > > current cpufreq core only support one cpufreq_driver. Others will fail > > except the first time. > > Then whoever gets there first wins. Make your driver register late and > if someone doesn't want to use it they can register a custom driver earlier. this driver did > > Rob > > >> Perhaps a > >> ranking is needed and this would only get enabled if there are no other > >> drivers and other conditions like having the clock "cpu" present are met. > > We'd better keep cpufreq core simple. For this driver, register cpufreq_driver > > is the last thing after checking all conditions. > > > >> > >> Rob > >> > >>>> Hi Grant & Rob, > >>>> > >>>> Could you comment? > >>>> > >>>>> > >>>>>> +- cpu-freqs : cpu frequency points it support > >>>>>> +- cpu-volts : cpu voltages required by the frequency point at the same index > >>>>>> +- trans-latency : transition_latency > >>>>>> diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig > >>>>>> index e24a2a1..216eecd 100644 > >>>>>> --- a/drivers/cpufreq/Kconfig > >>>>>> +++ b/drivers/cpufreq/Kconfig > >>>>>> @@ -179,6 +179,14 @@ config CPU_FREQ_GOV_CONSERVATIVE > >>>>>> > >>>>>> If in doubt, say N. > >>>>>> > >>>>>> +config GENERIC_CPUFREQ_DRIVER > >>>>>> + bool "Generic cpufreq driver using clock/regulator/devicetree" > >>>>>> + help > >>>>>> + This adds generic CPUFreq driver. It assumes all > >>>>>> + cores of the CPU share the same clock and voltage. > >>>>>> + > >>>>>> + If in doubt, say N. > >>>>> > >>>>> I think this needs dependencies on HAVE_CLK, OF and REGULATOR. > >>>> right, Thanks. I can not check clk before generic clock framework > >>>> come in. > >>>> Added: > >>>> depends on OF && REGULATOR > >>>> select CPU_FREQ_TABLE > >>> > >>> You can still use HAVE_CLK. That symbol has been around for ages and > >>> any platform implementing the clk API should select it so it's fine to > >>> depend on it even before there is a generic struct clk. > > You are right. Thanks. > > > > Richard > >>> > >>> Jamie > >> > >> _______________________________________________ > >> linux-arm-kernel mailing list > >> linux-arm-ker...@lists.infradead.org > >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > >> > > >
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