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    SubjectRE: [PATCH V2 13/32] omap_hsmmc: context save/restore support
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    > -----Original Message-----
    > From: Adrian Hunter [mailto:adrian.hunter@nokia.com]
    > Sent: Thursday, July 30, 2009 2:40 AM
    > To: Madhusudhan
    > Cc: 'Andrew Morton'; Lavinen Jarkko (Nokia-D/Helsinki); 'linux-omap
    > Mailing List'; 'Pierre Ossman'; Karpov Denis.2 (EXT-Teleca/Helsinki);
    > 'Matt Fleming'; 'lkml'
    > Subject: Re: [PATCH V2 13/32] omap_hsmmc: context save/restore support
    >
    > Madhusudhan wrote:
    > >
    > >> -----Original Message-----
    > >> From: linux-omap-owner@vger.kernel.org [mailto:linux-omap-
    > >> owner@vger.kernel.org] On Behalf Of Adrian Hunter
    > >> Sent: Tuesday, July 28, 2009 5:40 AM
    > >> To: Andrew Morton
    > >> Cc: Jarkko Lavinen; Adrian Hunter; linux-omap Mailing List; Pierre
    > Ossman;
    > >> Denis Karpov; Matt Fleming; lkml
    > >> Subject: [PATCH V2 13/32] omap_hsmmc: context save/restore support
    > >>
    > >> From 43e9fa346d7e386328876a8535dc8619bd1f47ae Mon Sep 17 00:00:00 2001
    > >> From: Denis Karpov <ext-denis.2.karpov@nokia.com>
    > >> Date: Wed, 22 Apr 2009 16:04:25 +0200
    > >> Subject: [PATCH] omap_hsmmc: context save/restore support
    > >>
    > >> Keep the context over PM dynamic OFF states.
    > >>
    > >> Signed-off-by: Denis Karpov <ext-denis.2.karpov@nokia.com>
    > >> Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
    > >> ---
    > >> drivers/mmc/host/omap_hsmmc.c | 194
    > >> ++++++++++++++++++++++++++++++++++++++--
    > >> 1 files changed, 184 insertions(+), 10 deletions(-)
    > >>
    > >> diff --git a/drivers/mmc/host/omap_hsmmc.c
    > b/drivers/mmc/host/omap_hsmmc.c
    > >> index c28d055..ac1a3bf 100644
    > >> --- a/drivers/mmc/host/omap_hsmmc.c
    > >> +++ b/drivers/mmc/host/omap_hsmmc.c
    > >> @@ -37,6 +37,7 @@
    > >>
    > >> /* OMAP HSMMC Host Controller Registers */
    > >> #define OMAP_HSMMC_SYSCONFIG 0x0010
    > >> +#define OMAP_HSMMC_SYSSTATUS 0x0014
    > >> #define OMAP_HSMMC_CON 0x002C
    > >> #define OMAP_HSMMC_BLK 0x0104
    > >> #define OMAP_HSMMC_ARG 0x0108
    > >> @@ -94,6 +95,8 @@
    > >> #define DUAL_VOLT_OCR_BIT 7
    > >> #define SRC (1 << 25)
    > >> #define SRD (1 << 26)
    > >> +#define SOFTRESET (1 << 1)
    > >> +#define RESETDONE (1 << 0)
    > >>
    > >> /*
    > >> * FIXME: Most likely all the data using these _DEVID defines should
    > come
    > >> @@ -152,6 +155,8 @@ struct mmc_omap_host {
    > >> int slot_id;
    > >> int dbclk_enabled;
    > >> int response_busy;
    > >> + int context_loss;
    > >> +
    > >> struct omap_mmc_platform_data *pdata;
    > >> };
    > >>
    > >> @@ -166,6 +171,166 @@ static void omap_mmc_stop_clock(struct
    > mmc_omap_host
    > >> *host)
    > >> dev_dbg(mmc_dev(host->mmc), "MMC Clock is not stoped\n");
    > >> }
    > >>
    > >> +#ifdef CONFIG_PM
    > >> +
    > >> +/*
    > >> + * Restore the MMC host context, if it was lost as result of a
    > >> + * power state change.
    > >> + */
    > >> +static int omap_mmc_restore_ctx(struct mmc_omap_host *host)
    > >> +{
    > >> + struct mmc_ios *ios = &host->mmc->ios;
    > >> + struct omap_mmc_platform_data *pdata = host->pdata;
    > >> + int context_loss = 0;
    > >> + u32 hctl, capa, con;
    > >> + u16 dsor = 0;
    > >> + unsigned long timeout;
    > >> +
    > >> + if (pdata->get_context_loss_count) {
    > >> + context_loss = pdata->get_context_loss_count(host->dev);
    > >> + if (context_loss < 0)
    > >> + return 1;
    > >> + }
    > > This seems to restore the context always. The context should be restored
    > > only if the card was powered OFF, Right?
    >
    > Not exactly. The "context" is just the host controller registers, which
    > get
    > lost if power management decides to power off the host controller, which
    > it
    > will if it decides it is not doing anything. For us, switching off the
    > functional clock lets PM power off the host controller. The card can be
    > in
    > any power state: on, off, card/regulator sleep.
    >
    > The context is restored only when it has been lost - see the following
    > lines. But this is done from the "enable" method, so this is only called
    > if someone is trying to access the card.
    >
    > + dev_dbg(mmc_dev(host->mmc), "context was %slost\n",
    > + context_loss == host->context_loss ? "not " : "");
    > + if (host->context_loss == context_loss)
    > + return 1;
    >
    > And then further down, we skip some things if the card is off:
    >
    > + /* Do not initialize card-specific things if the power is off */
    > + if (host->power_mode == MMC_POWER_OFF)
    > + goto out;
    >
    >
    > > The context could also be lost if the CORE transitions to OFF. I assume
    > that
    > > case gets handled here without anything extra required if "power_saving"
    > is
    > > set to true. Am I right?
    >
    > Yes, "power_saving" is not related to "Power Management". "power_saving"
    > is about controlling the power regulators, which the host controller does
    > itself without any support from PM.
    >
    > To put it another way, "power_saving" and CONFIG_PM can be set
    > independently
    > of one another.

    But the "omap_hsmmc_context_save" and " omap_hsmmc_context_restore" are
    under CONFIG_PM. They are empty functions if CONFIG_PM is not set. Does this
    mean that if CONFIG_PM is not set the host regulators are not turned OFF
    even if there is no activity on MMC?

    >
    > > How about the case of eMMC? Since it is not a removable device the card
    > is
    > > not powered OFF. But the CORE OFF would result in context loss. Do we
    > hit
    > > the restore_ctx path in that case?
    >
    > On the contrary, eMMC *is* powered off. After 100ms of inactivity, eMMC
    > is
    > put to card sleep, and the regulator is put to sleep also - in fact there
    > are two regulators and one is powered off here. After 8 seconds
    > the other regulator is powered off and consequently after that the eMMC
    > must
    > be reinitialised (rescanned) before it can be used.




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