From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: sdhci: runtime suspend/resume on card insert/removal
Date: Mon, 14 Sep 2015 12:00:23 +0100 [thread overview]
Message-ID: <20150914110023.GK21084@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <20150914105014.GJ21084@n2100.arm.linux.org.uk>
On Mon, Sep 14, 2015 at 11:50:14AM +0100, Russell King - ARM Linux wrote:
> On Mon, Sep 14, 2015 at 03:45:43PM +0530, Vaibhav Hiremath wrote:
> > Came across below lines in the datasheet,
> >
> > ========= Copy-n-paste from datasheet============
> >
> > All SDH interfaces share the same clock which is enabled when any of the SDH
> > clock enables are
> > set (from PMUA_SDH1_CLK_RES_CTRL, PMUA_SDH2_CLK_RES_CTRL,
> > PMUA_SDH3_CLK_RES_CTRL, PMUA_SDH4_CLK_RES_CTRL,
> > PMUA_SDH5_CLK_RES_CTRL), with clock source select and divider ratio
> > controlled by
> > PMUA_SDH1_CLK_RES_CTRL.
> >
> > ==================================================
> >
> >
> > And I can confirm that after disabling AXI interface clock for all the
> > SDH modules (1-5) I see I get an abort.
> >
> > This clearly explains/justifies/proves that the existing code is
> > working as expected. I have eMMC mounted on the board, which makes
> > clock to always stay ON on SDH3.
> >
> > So there is an OR gate implemented inside which takes input from
> > SDHx_AXI_EN and feeds back to all SDHx instances. Don't ask me why it
> > has been designed that way :)
> >
> > And I did some experiment as well, so what I have observed is,
> > SDH_AXI_CLOCK is required to generate card detection, without that I do
> > not see card detection working.
>
> What that means is that if DT configures the interface to use its
> internal card detection, the AXI clock must never shut off when entering
> runtime-PM.
>
> Yes, it means you don't get the same savings as you would by turning
> off that clock, but that's the choice between using the internal card
> detection and a GPIO for this. The code shouldn't force you to use a
> GPIO just because the Linux driver implementation dumbly disables the
> AXI clock.
Note that should also happen if a SDIO card is inserted, and the SDIO IRQ
is enabled - so the SDIO card can signal an interrupt back to the host.
--
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
WARNING: multiple messages have this Message-ID (diff)
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Cc: Jisheng Zhang <jszhang@marvell.com>,
ulf.hansson@linaro.org,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
nico@fluxnic.net
Subject: Re: sdhci: runtime suspend/resume on card insert/removal
Date: Mon, 14 Sep 2015 12:00:23 +0100 [thread overview]
Message-ID: <20150914110023.GK21084@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <20150914105014.GJ21084@n2100.arm.linux.org.uk>
On Mon, Sep 14, 2015 at 11:50:14AM +0100, Russell King - ARM Linux wrote:
> On Mon, Sep 14, 2015 at 03:45:43PM +0530, Vaibhav Hiremath wrote:
> > Came across below lines in the datasheet,
> >
> > ========= Copy-n-paste from datasheet============
> >
> > All SDH interfaces share the same clock which is enabled when any of the SDH
> > clock enables are
> > set (from PMUA_SDH1_CLK_RES_CTRL, PMUA_SDH2_CLK_RES_CTRL,
> > PMUA_SDH3_CLK_RES_CTRL, PMUA_SDH4_CLK_RES_CTRL,
> > PMUA_SDH5_CLK_RES_CTRL), with clock source select and divider ratio
> > controlled by
> > PMUA_SDH1_CLK_RES_CTRL.
> >
> > ==================================================
> >
> >
> > And I can confirm that after disabling AXI interface clock for all the
> > SDH modules (1-5) I see I get an abort.
> >
> > This clearly explains/justifies/proves that the existing code is
> > working as expected. I have eMMC mounted on the board, which makes
> > clock to always stay ON on SDH3.
> >
> > So there is an OR gate implemented inside which takes input from
> > SDHx_AXI_EN and feeds back to all SDHx instances. Don't ask me why it
> > has been designed that way :)
> >
> > And I did some experiment as well, so what I have observed is,
> > SDH_AXI_CLOCK is required to generate card detection, without that I do
> > not see card detection working.
>
> What that means is that if DT configures the interface to use its
> internal card detection, the AXI clock must never shut off when entering
> runtime-PM.
>
> Yes, it means you don't get the same savings as you would by turning
> off that clock, but that's the choice between using the internal card
> detection and a GPIO for this. The code shouldn't force you to use a
> GPIO just because the Linux driver implementation dumbly disables the
> AXI clock.
Note that should also happen if a SDIO card is inserted, and the SDIO IRQ
is enabled - so the SDIO card can signal an interrupt back to the host.
--
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2015-09-14 11:00 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-10 7:10 sdhci: runtime suspend/resume on card insert/removal Vaibhav Hiremath
2015-09-10 7:10 ` Vaibhav Hiremath
2015-09-10 7:31 ` Jisheng Zhang
2015-09-10 7:31 ` Jisheng Zhang
2015-09-10 7:51 ` Vaibhav Hiremath
2015-09-10 7:51 ` Vaibhav Hiremath
2015-09-10 7:57 ` Jisheng Zhang
2015-09-10 7:57 ` Jisheng Zhang
2015-09-10 8:02 ` Russell King - ARM Linux
2015-09-10 8:02 ` Russell King - ARM Linux
2015-09-10 8:04 ` Jisheng Zhang
2015-09-10 8:04 ` Jisheng Zhang
2015-09-14 6:25 ` Vaibhav Hiremath
2015-09-14 6:25 ` Vaibhav Hiremath
2015-09-14 6:28 ` Jisheng Zhang
2015-09-14 6:28 ` Jisheng Zhang
2015-09-14 8:13 ` Vaibhav Hiremath
2015-09-14 8:13 ` Vaibhav Hiremath
2015-09-14 8:18 ` Jisheng Zhang
2015-09-14 8:18 ` Jisheng Zhang
2015-09-14 9:19 ` Vaibhav Hiremath
2015-09-14 9:19 ` Vaibhav Hiremath
2015-09-14 10:15 ` Vaibhav Hiremath
2015-09-14 10:15 ` Vaibhav Hiremath
2015-09-14 10:50 ` Russell King - ARM Linux
2015-09-14 10:50 ` Russell King - ARM Linux
2015-09-14 11:00 ` Russell King - ARM Linux [this message]
2015-09-14 11:00 ` Russell King - ARM Linux
2015-09-14 12:33 ` Vaibhav Hiremath
2015-09-14 12:33 ` Vaibhav Hiremath
2015-09-14 12:49 ` Russell King - ARM Linux
2015-09-14 12:49 ` Russell King - ARM Linux
2015-09-14 13:05 ` Vaibhav Hiremath
2015-09-14 13:05 ` Vaibhav Hiremath
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