linux-kernel - Re: [PATCH] spi: imx: Revert "spi: imx: enable runtime pm support"

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Date:   Fri, 9 Oct 2020 09:48:29 +0200
From:   Christian Eggers <ceggers@...i.de>
To:     Sascha Hauer <s.hauer@...gutronix.de>
CC:     Mark Brown <broonie@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        <linux-spi@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] spi: imx: Revert "spi: imx: enable runtime pm support"

Hi Sascha,

On Friday, 9 October 2020, 09:39:44 CEST, Sascha Hauer wrote:
> On Fri, Oct 09, 2020 at 06:27:38AM +0200, Christian Eggers wrote:
> > This reverts commit 525c9e5a32bd7951eae3f06d9d077fea51718a6c.
> > 
> > If CONFIG_PM is disabled, the system completely freezes on probe as
> > nothing enables the clock of the SPI peripheral.
> 
> Instead of reverting it, why not just fix it?
I expect that 5.9 will be released soon. I think that in this late stage 
reverting is more safe than fixing...

> Normally the device should be brought to active state manually in probe
> before pm_runtime takes over, then CONFIG_PM disabled doesn't hurt.
> Using pm_runtime to put the device to active state initially has the
> problem you describe.
Thanks for the hint. I've no experience in runtime power management. If you 
could provide a patch against the current version, I can make a quick test. I 
can also try to fix it myself, but this will take until next week.

Best regards
Christian