Re: [PATCH V2 13/32] omap_hsmmc: context save/restore support
From: Adrian Hunter
Date: Thu Jul 30 2009 - 15:33:21 EST
ext Madhusudhan wrote:
-----Original Message-----
From: Adrian Hunter [mailto:adrian.hunter@xxxxxxxxx]
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@xxxxxxxxxxxxxxx [mailto:linux-omap-
owner@xxxxxxxxxxxxxxx] 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@xxxxxxxxx>
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@xxxxxxxxx>
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
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?
No. Context save/restore *is* a part of Power Management. It is needed
to support Dynamic Power Switching (DPS).
The voltage regulators are controlled via the enable/disable methods
even when CONFIG_PM is not defined.
Note that the voltage regulators to which I refer, power the cards not
the host controllers.
So the power to the host controller is under the control of Power Management
and is supported by context save/restore.
The power to the cards is controlled by the driver (omap_hsmmc) using the
enable/disable methods.
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