Dear Daniel, On Mon, 2 Nov 2015 09:48:38 +0100 Daniel Lezcano wrote:
> On 11/02/2015 03:51 AM, Jisheng Zhang wrote: > > Dear Daniel, > > > > On Fri, 30 Oct 2015 13:37:01 +0100 > > Daniel Lezcano wrote: > > > >> On 10/30/2015 12:09 PM, Jisheng Zhang wrote: > >>> Dear Daniel, > >>> > >>> On Fri, 30 Oct 2015 11:44:46 +0100 > >>> Daniel Lezcano <daniel.lezcano@....> wrote: > >>> > >>>> On 10/30/2015 09:27 AM, Jisheng Zhang wrote: > >>>>> Implement an ARM delay timer to be used for udelay(). This allows us to > >>>>> skip the delay loop calibration at boot on Marvell BG2, BG2Q, BG2CD > >>>>> platforms. And after this patch, udelay() will be unaffected by CPU > >>>>> frequency changes. > >>>>> > >>>>> Signed-off-by: Jisheng Zhang <[email protected]> > >>>>> --- > >>>>> drivers/clocksource/Kconfig | 10 ++++++++++ > >>>>> drivers/clocksource/dw_apb_timer_of.c | 16 ++++++++++++++++ > >>>>> 2 files changed, 26 insertions(+) > >>>>> > >>>>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig > >>>>> index a7726db..7b081805 100644 > >>>>> --- a/drivers/clocksource/Kconfig > >>>>> +++ b/drivers/clocksource/Kconfig > >>>>> @@ -29,6 +29,16 @@ config DW_APB_TIMER_OF > >>>>> select DW_APB_TIMER > >>>>> select CLKSRC_OF > >>>>> > >>>>> +config DW_APB_TIMER_BASED_DELAY > >>>>> + bool "DW APB timer based delay" > >>>>> + depends on ARM && DW_APB_TIMER_OF > >>>>> + default n > >>>>> + help > >>>>> + This option enables support for using the DW APB timer to > >>>>> + implement timer-based delay. It is useful for skiping the > >>>>> + delay loop calibration at boot on some platforms. And the > >>>>> + udelay() will be unaffected by CPU frequency changes. > >>>>> + > >>>> > >>>> Why do you want it to be optional ? > >>>> > >>> > >>> Because in some platforms which has arm arch timer, this dw apb timer > >>> delay isn't needed, the arch timer is better. So we want it be optional > >>> so that the platforms which need this feature select it manually when > >>> config > >>> the kernel. > >> > >> Correct me if I am wrong. If you have the arch timer, you don't need the > > > > Yes, I don't need the dw apb timer if we have arch timer, > > > >> dw apb timer at all, no ? So the selection would be arch arm timer *or* > >> dw_apb_timer ? not arch_arm_timer for delay and dw_apb_timer for > >> clockevents, right ? > > > > Yes, if we have arch timer, I prefer to use it for clockevent and delay. > > > > Could you please provide suggestion how to handle this case? > > If I follow the logic of arch_arm_timer is better than dw_apb timer. > > 1. The arch_arm_timer is present > > => dw_apb timer is not used at all > > CONFIG_ARM_ARCH_TIMER=y > # CONFIG_DW_APB_TIMER is not set > > 2. The arch_arm_timer is *not* present > > => dw_apb_timer is used with delay code > > # CONFIG_ARM_ARCH_TIMER is not set > CONFIG_DW_APB_TIMER=y > > In both cases, DW_APB_TIMER_BASED_DELAY is not needed. > The problem is register_current_timer_delay() is only available in ARM but DW APB timer isn't only used in ARM platforms, but also ARM64 etc. where the register_current_timer_delay() isn't defined. so I used DW_APB_TIMER_BASED_DELAY to 1. distinguish whether we need the dw apb timer based delay 2. distinguish whether we have register_current_timer_delay() I have a solution which doesn't need DW_APB_TIMER_BASED_DELAY symbol -- put all timer based delay code under CONFIG_ARM, I'm not sure whether this is better. Could you please give suggestion? Thanks in advance, Jisheng -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
