linux-kernel - Re: [RFC PATCH 0/4] mmc: sdhci: Support maximum DMA latency request via PM QoS

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Date:	Tue, 24 Mar 2015 21:13:01 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Adrian Hunter <adrian.hunter@...el.com>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Kevin Hilman <khilman@...aro.org>,
	Tomeu Vizoso <tomeu.vizoso@...labora.com>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/4] mmc: sdhci: Support maximum DMA latency request via PM QoS

On Tuesday, March 24, 2015 03:40:36 PM Adrian Hunter wrote:
> Hi
> 
> Here are some patches to address an issue with SDHCI
> in Intel Baytrail. Intel Baytrail has been observed
> sometimes to hang if host controllers are using DMA
> while deep C-states are used. Workaround that by
> specifying a maximum DMA latency that will prevent
> deep C-states.
> 
> The first patch adds a new PM QOS function so that
> the SDHCI driver can do a "lazy" cancel of the QoS
> request from within its "finish" tasklet.
> 
> The second patch adds support to SDHCI for specifying a
> maximum DMA latency.
> 
> The third and fourth patches take that facility into
> use for Baytrail.
> 
> Ad hoc testing with Lenovo Thinkpad 10 showed a stress
> test could run for at least 24 hours with the patches,
> compared to less than an hour without.
> 
> These patches are on top of my driver strength patches
> which are on top of my re-tuning patches.
> 
> 
> Adrian Hunter (4):
>       PM / QoS: Add pm_qos_cancel_request_lazy() that doesn't sleep
>       mmc: sdhci: Support maximum DMA latency request via PM QOS
>       mmc: sdhci-acpi: Fix device hang on Intel BayTrail
>       mmc: sdhci-pci: Fix device hang on Intel BayTrail

I'm a bit concerned about the CPUID-based blacklisting of things and
whether or not the SDHCI driver is the right place for doing that.

Maybe we should do it from within the LPSS driver instead?


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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