Re: [PATCH v3] ARM: imx6q: cpuidle: fix bug that CPU might not wake up at expected time

From: Kohji Okuno <okuno.kohji@jp.panasonic.com>
To: <peng.fan@nxp.com>, <shawnguo@kernel.org>
Cc: s.hauer@pengutronix.de, okuno.kohji@jp.panasonic.com,
	linux-imx@nxp.com, kernel@pengutronix.de, fabio.estevam@nxp.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3] ARM: imx6q: cpuidle: fix bug that CPU might not wake up at expected time
Date: Thu, 7 Mar 2019 09:06:55 +0900	[thread overview]
Message-ID: <20190307.090655.976331005358729399.okuno.kohji@jp.panasonic.com> (raw)
In-Reply-To: <AM0PR04MB4481F511300E3E95827E0D5D88730@AM0PR04MB4481.eurprd04.prod.outlook.com>

Hi Peng and Shawn,

Peng, thank you for sharing information and I'm very sorry about my
comment.

Shawn and Peng,
Could you confirm about the addition patch for pm-imx6.c?

Best regards,
 Kohji Okuno

Peng Fan <peng.fan@nxp.com> wrote:
> 
> 
>> -----Original Message-----
>> From: Kohji Okuno [mailto:okuno.kohji@jp.panasonic.com]
>> Sent: 2019年3月5日 18:38
>> To: shawnguo@kernel.org
>> Cc: linux-arm-kernel@lists.infradead.org; s.hauer@pengutronix.de;
>> kernel@pengutronix.de; Fabio Estevam <fabio.estevam@nxp.com>;
>> dl-linux-imx <linux-imx@nxp.com>; okuno.kohji@jp.panasonic.com
>> Subject: Re: [PATCH v3] ARM: imx6q: cpuidle: fix bug that CPU might not wake
>> up at expected time
>> 
>> Hi Shawn,
>> 
>> I found the fix of the same issue on linux-imx repository. Could you refer to
>> the following?
>> 
>> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsour
>> ce.codeaurora.org%2Fexternal%2Fimx%2Flinux-imx%2Fcommit%2F%3Fh%3D
>> imx_4.1.y_brillo%26id%3Df739483488ef76979c06efea397237756bec45b9&a
>> mp;data=02%7C01%7Cpeng.fan%40nxp.com%7Cf02b29e33b2c4245a60d08d
>> 6a156ad72%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C636873
>> 790983230223&amp;sdata=QM21UkcAUjjZq3kPdZEgrkCxvFTneGRH7%2BlQg
>> GJNHoU%3D&amp;reserved=0
>> 
>> Regarding the fix of cpuidle-imx6q.c, my fix is better, I think.
>> But, we may also need to modify pm-imx6.c.
>> 
>> # I cannot understand why they doesn't release their modifications.
> 
> This patch has been tried to upstream long time ago, https://lkml.org/lkml/2017/12/30/65
> 
> Regards,
> Peng
> 
>> 
>> Best regards,
>>  Kohji Okuno
>> 
>> Shawn Guo <shawnguo@kernel.org> wrote:
>> > On Tue, Feb 26, 2019 at 11:34:13AM +0900, Kohji Okuno wrote:
>> >>  In the current cpuidle implementation for i.MX6q, the CPU that sets
>> >> 'WAIT_UNCLOCKED' and the CPU that returns to 'WAIT_CLOCKED' are
>> >> always the same. While the CPU that sets 'WAIT_UNCLOCKED' is in IDLE
>> >> state of "WAIT", if the other CPU wakes up and enters IDLE state of "WFI"
>> >> istead of "WAIT", this CPU can not wake up at expired time.
>> >>  Because, in the case of "WFI", the CPU must be waked up by the local
>> >> timer interrupt. But, while 'WAIT_UNCLOCKED' is set, the local timer
>> >> is stopped, when all CPUs execute "wfi" instruction. As a result, the
>> >> local timer interrupt is not fired.
>> >>  In this situation, this CPU will wake up by IRQ different from local
>> >> timer. (e.g. broacast tiemr)
>> >
>> > s/tiemr/timer
>> >
>> >>
>> >> So, this fix changes CPU to return to 'WAIT_CLOCKED'.
>> >>
>> >> Signed-off-by: Kohji Okuno <okuno.kohji@jp.panasonic.com>
>> >
>> > Applied the patch with following Fixes tag.
>> >
>> > Fixes: e5f9dec8ff5f ("ARM: imx6q: support WAIT mode using cpuidle")
>> >
>> > Thanks for the fixing.
>> >
>> > Shawn

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