From: javier.martinez@collabora•co.uk (Javier Martinez Canillas)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 5/6] ARM: dts: Add vmmc and vqmmc supplies for Peach Pit and Pi boards
Date: Wed, 20 Aug 2014 11:49:24 +0200 [thread overview]
Message-ID: <53F46F24.9020800@collabora.co.uk> (raw)
In-Reply-To: <CAD=FV=V9oct-iJ==1SLdxusq68AY3utMQF+MbX0Uf+2dC0mwww@mail.gmail.com>
Hello Doug,
On 08/19/2014 06:26 PM, Doug Anderson wrote:
>
> While your change is correct, I have a worry that it will break things
> if it's merged before some patches that Yuvaraj is working on.
>
> Specifically the problem on pit and pi (and any exynos5250 / 5420 /
> 5800 / ... boards using the built-in "card detect") is that the card
> detect line is on the same power rail as "vqmmc". That means you
> can't turn off vqmmc if you still need to be able to detect card
> insertions.
>
> ...but you can't turn off vmmc without turning off vqmmc, otherwise
> current will leak through the IO lines into the card, which is bad.
>
>
> Right now the SDMMC core will try to turn off power to the card at two times:
> 1. when the card is ejected
> 2. when it's trying to reset the card
>
>
> Obviously the first problem is a huge problem on exynos because it
> means that we won't be able to detect card insertions. ...but we
> still want to turn the power off from #2. To really fix the problem I
> think the core needs to be extended to treat the above as two separate
> cases.
>
Thanks a lot for the explanation, now I remember reading about this on
thread "[PATCH 2/3] mmc: dw_mmc: Dont cut off vqmmc and vmmc" [0] but
didn't think in the side effect when adding this patch...
>
> Your patch might work at the moment because I think dw_mmc doesn't
> actually try to turn off these rails with the main SDMMC core asks it
> to. ...but I still worry about merging them before Yuvaraj's changes
> are ready.
>
Agreed, I'll drop this patch and wait for Yuvaraj's series to land first.
Yuvaraj's "UHS support for dw_mmc driver" series that should contain the
change you are referring had the issue that when the tps65090 fet4 was
used as vmmc-supply, mmc_regulator_get_supply() was failing.
I posted a bunch of patches to fix that issue and there were already
merged on the relevant trees and shows on linux-next:
e1da8cd mmc: core: Use regulator_get_voltage() if OCR mask is empty.
a130548 ARM: dts: Improve Peach Pit and Pi power scheme
4f2352c regulator: tps65090: Set voltage for fixed regulators
26988ef regulator: core: Allow to get voltage count and list from parent
e303996 regulator: core: Get voltage from parent if not available
So hopefully his series have no blockers anymore.
>
> -Doug
>
Best regards,
Javier
[0]: https://www.mail-archive.com/linux-mmc at vger.kernel.org/msg27152.html
next prev parent reply other threads:[~2014-08-20 9:49 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-19 15:08 [PATCH 0/6] Add max77802 support for Peach boards Javier Martinez Canillas
2014-08-19 15:08 ` [PATCH 1/6] ARM: dts: Add Peach Pit and Pi dts entry for max77802 PMIC Javier Martinez Canillas
2014-08-19 18:52 ` Andreas Färber
2014-08-20 10:27 ` Javier Martinez Canillas
2014-08-19 15:08 ` [PATCH 2/6] ARM: dts: add hdmi regulators for exynos5800 based peach-pi board Javier Martinez Canillas
2014-09-10 4:44 ` Doug Anderson
2014-09-10 4:45 ` Doug Anderson
2014-09-10 9:00 ` Javier Martinez Canillas
2014-08-19 15:08 ` [PATCH 3/6] ARM: dts: add hdmi regulators for exynos5420 based peach-pit board Javier Martinez Canillas
2014-08-19 15:08 ` [PATCH 4/6] ARM: dts: Add thermistor dts fragment used by exynos based Peach boards Javier Martinez Canillas
2014-08-19 15:08 ` [PATCH 5/6] ARM: dts: Add vmmc and vqmmc supplies for Peach Pit and Pi boards Javier Martinez Canillas
2014-08-19 16:26 ` Doug Anderson
2014-08-20 9:49 ` Javier Martinez Canillas [this message]
2014-08-19 18:37 ` Andreas Färber
2014-08-20 10:21 ` Javier Martinez Canillas
2014-08-20 10:36 ` Javier Martinez Canillas
2014-08-19 15:08 ` [PATCH 6/6] ARM: dts: Add Peach Pit and Pi dts entry for ISL29018 sensor Javier Martinez Canillas
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