On 2018-01-09 11:13, Lucas Stach wrote: > Am Dienstag, den 09.01.2018, 09:25 +0000 schrieb Anson Huang: >> >> Best Regards! >> Anson Huang >> >> >> > -----Original Message----- >> > From: Dong Aisheng [mailto:dongas86@xxxxxxxxx] >> > Sent: 2018-01-09 5:23 PM >> > To: Stefan Agner <stefan@xxxxxxxx> >> > Cc: shawnguo@xxxxxxxxxx; kernel@xxxxxxxxxxxxxx; Fabio Estevam >> > <fabio.estevam@xxxxxxx>; robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx; >> > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; >> > linux- >> > kernel@xxxxxxxxxxxxxxx; Anson Huang <anson.huang@xxxxxxx>; dl- >> > linux-imx >> > <linux-imx@xxxxxxx> >> > Subject: Re: [PATCH 1/7] ARM: imx: add timer stop flag to ARM power >> > off state >> > >> > On Tue, Jan 02, 2018 at 05:42:17PM +0100, Stefan Agner wrote: >> > > When the CPU is in ARM power off state the ARM architected timers >> > > are >> > > stopped. The flag is already present in the higher power WAIT >> > > mode. >> > > >> > > This allows to use the ARM generic timer on i.MX 6UL/6ULL SoC. >> > > Without the flag the kernel freezes when the timer enters the >> > > first >> > > time ARM power off mode. >> > > >> > > Cc: Anson Huang <anson.huang@xxxxxxx> >> > > Signed-off-by: Stefan Agner <stefan@xxxxxxxx> >> > >> > It seems ok at my side. >> > Did you meet the real issue? If yes, how to reproduce? >> > >> > Both mx6sx and mx6ul are using GPT which do not need that flag, >> > suppose we >> > should remove it, right? >> > Anson can help confirm it. >> >> For UP system like i.MX6SX, we do NOT enable "cortex-a9-twd-timer", >> so local >> timer is NOT used, GPT is used instead, GPT's clock is NOT disabled >> when cpuidle, >> so I think we should remove all these Timer stop flag for 6SX >> CPUIDLE. > > It's correct to set the flag even on UP systems, as the flag means the > CPU _local_ timer is stopped in this sleep mode. Also there are systems > out there which are using the TWD on UP, as it operates at a higher > frequency leading to better wakeup granularity. Documentation/devicetree/bindings/arm/twd.txt states that TWD provides "per-cpu local timer". But as far as I can see TWD still uses SPI interrupts, routed through GIC, so is this the differentiation? -- Stefan -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
