linux-kernel - RE: [PATCH v2 4/5] spi: tegra210-quad: add acpi support

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Message-ID: <DM4PR12MB5769C42A0DFD716508CD737CC33E9@DM4PR12MB5769.namprd12.prod.outlook.com>
Date:   Fri, 25 Feb 2022 04:19:49 +0000
From:   Krishna Yarlagadda <kyarlagadda@...dia.com>
To:     Mark Brown <broonie@...nel.org>
CC:     "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        Sowjanya Komatineni <skomatineni@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>
Subject: RE: [PATCH v2 4/5] spi: tegra210-quad: add acpi support

> -----Original Message-----
> From: Mark Brown <broonie@...nel.org>
> Sent: 24 February 2022 23:52
> To: Krishna Yarlagadda <kyarlagadda@...dia.com>
> Cc: thierry.reding@...il.com; Jonathan Hunter <jonathanh@...dia.com>; linux-spi@...r.kernel.org; linux-tegra@...r.kernel.org;
> Sowjanya Komatineni <skomatineni@...dia.com>; Laxman Dewangan <ldewangan@...dia.com>; robh+dt@...nel.org;
> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; p.zabel@...gutronix.de
> Subject: Re: [PATCH v2 4/5] spi: tegra210-quad: add acpi support
> 
> On Wed, Feb 23, 2022 at 06:32:56AM +0000, Krishna Yarlagadda wrote:
> 
> > > > +	if (has_acpi_companion(tqspi->dev))
> > > > +		return 0;
> > > >  	/* flush all write which are in PPSB queue by reading back */
> > > >  	tegra_qspi_readl(tqspi, QSPI_COMMAND1);
> 
> > > As well as clock stuff this is also skipping flushing of pending writes
> > > - is that intentional?  It's not called out in the changelog and seems like
> > > something that could cause issues if someone runs on a system where
> > > the firmware does implement runtime suspend.
> 
> > Runtime suspend is not enabled with ACPI firmware. Converted compiler flag in v1 to runtime check.
> > We must add more changes like setting DPM flags for runtime pm support with ACPI.
> > Can take this as part of a different series.
> 
> It at least needs to be clearer what's going on here, the changelog
> doesn't match the code and it's not obvious from the code that ACPI
> won't kick in and power manage the device as things stand.
Understood Mark. I will add comments to make it clear.
Also update change log indicating runtime suspend does not work
with ACPI.