From mboxrd@z Thu Jan 1 00:00:00 1970 From: Srinivas Kandagatla Subject: Re: [PATCH] clocksource: arm_global_timer: Detect if gt is usable with CPU_FREQ Date: Tue, 14 Apr 2015 08:41:04 +0100 Message-ID: <552CC490.4010002@linaro.org> References: <552BFED9.3020105@adapteva.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <552BFED9.3020105-hhg9azYwhpdWk0Htik3J/w@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ola Jeppsson , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org Cc: devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Arnd Bergmann , Srinivas Kandagatla , Michal Simek , Stuart Menefy , Olof Johansson , =?windows-1252?Q?S=F6ren_Brinkmann?= , Peter Griffin , Maxime Coquelin List-Id: devicetree@vger.kernel.org +Adding Pete and Maxime Hi Ola, Thankyou for sending the patch, I like the Idea, but I have some specific concerns which would break existing SOCs. On 13/04/15 18:37, Ola Jeppsson wrote: > Some Cortex A9 CPU:s (e.g. zynq) have the tick tied to the CPU > frequency. On those CPU:s we cannot use the global-timer as a reliable > clocksource with CPU frequency scaling enabled since this is not > currently taken into account by the driver. > > Add a "tied-to-cpu-freq" boolean to the global-timer dt node indicate > this condition. > > When the global-timer register function sees this property return > immediately and don't register the clocksource. > > Signed-off-by: Ola Jeppsson > --- > Documentation/devicetree/bindings/arm/global_timer.txt | 4 ++++ > drivers/clocksource/arm_global_timer.c | 7 +++++++ > 2 files changed, 11 insertions(+) > > diff --git a/Documentation/devicetree/bindings/arm/global_timer.txt b/Documentation/devicetree/bindings/arm/global_timer.txt > index bdae3a818793..465e02c17b5b 100644 > --- a/Documentation/devicetree/bindings/arm/global_timer.txt > +++ b/Documentation/devicetree/bindings/arm/global_timer.txt > @@ -17,6 +17,10 @@ > > - clocks : Should be phandle to a clock. > > +** Timer node optional properties: > + > +- tied-to-cpu-freq : indicates that the timer scales with the CPU frequency. > + > Example: > > timer@2c000600 { > diff --git a/drivers/clocksource/arm_global_timer.c b/drivers/clocksource/arm_global_timer.c > index e6833771a716..8913ebda3f09 100644 > --- a/drivers/clocksource/arm_global_timer.c > +++ b/drivers/clocksource/arm_global_timer.c > @@ -268,6 +268,13 @@ static void __init global_timer_of_register(struct device_node *np) > return; > } > > +#ifdef CONFIG_CPU_FREQ > + if (of_property_read_bool(np, "tied-to-cpu-freq")) { > + pr_warn("global-timer: tied to cpu frequency, not supported with scaling\n"); > + return; > + } > +#endif > + This patch would not let the SOC like STiH415/416 or zynq with "tied-to-cpu-freq" property to boot with multi_v7_defconfig. Which is not correct thing to do, as STi SOC's do not use cpufreq driver however the tick is tied to this clocksource. --srini > gt_clk = of_clk_get(np, 0); > if (!IS_ERR(gt_clk)) { > err = clk_prepare_enable(gt_clk); > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html