From: Zach Brown <zach.brown@ni.com>
To: Adrian Hunter <adrian.hunter@intel.com>
Cc: ulf.hansson@linaro.org, mark.rutland@arm.com, robh+dt@kernel.org,
linux-mmc@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sdhci: Add quirk and device tree parameter to force SD test mode
Date: Tue, 23 Aug 2016 17:14:22 -0500 [thread overview]
Message-ID: <20160823221421.GB20351@zach-desktop> (raw)
In-Reply-To: <684dd3fb-15ac-fa84-2f1e-89f379b5149a@intel.com>
On Tue, Aug 23, 2016 at 09:22:29AM +0300, Adrian Hunter wrote:
> On 23/08/16 01:55, Zach Brown wrote:
> > From: Jaeden Amero <jaeden.amero@ni.com>
> >
> > On some devices, CD is broken so that we must force the SDHCI into test
> > mode and set CD, so that it always detects an SD card as present.
> >
> > In order to get a device with broken CD working, we had previously
> > always set the SDHCI into test mode. Unfortunately, this had the side
> > effect of making all SD cards used with our Linux kernels undetectable
> > and non-removable.
> >
> > By making this "SD test mode" setting optional via a quirk, we can avoid
> > this side effect for devices other than the device with broken CD.
> > Additionally, we add a device parameter to sdhci-pltfm to allow all
> > SDHCI drivers to enable this quirk.
>
> Generally new quirks are not acceptable, but I don't see how test mode helps
> very much since you still don't get any card detection events. If you
> really need test mode, please explain more about how it helps (as opposed to
> polling for example).
>
>
Polling doesnt work in our case, since the issue lies with the SD controller
itself. The SD controller in xilinx zynq devices requires the CDn signal to
work. http://www.xilinx.com/support/answers/61064.html We have a situation
where the controller requires the signal, but we can't use any of our pins to
supply it. With test mode we can get the controller into a state where it works
despite not having the signal.
next prev parent reply other threads:[~2016-08-23 22:14 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-22 22:55 [PATCH] sdhci: Add quirk and device tree parameter to force SD test mode Zach Brown
2016-08-23 2:46 ` Frank Rowand
2016-08-23 22:19 ` Zach Brown
[not found] ` <1471906531-28668-1-git-send-email-zach.brown-acOepvfBmUk@public.gmane.org>
2016-08-23 1:34 ` Haibo Chen
2016-08-23 22:04 ` Zach Brown
2016-08-23 6:22 ` Adrian Hunter
2016-08-23 22:14 ` Zach Brown [this message]
2016-08-24 6:16 ` Adrian Hunter
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