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Message-ID: <1289927869-14519-1-git-send-email-linus.walleij@stericsson.com>
Date: Tue, 16 Nov 2010 18:17:49 +0100
From: Linus Walleij <linus.walleij@...ricsson.com>
To: <linux-mmc@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>
Cc: <akpm@...ux-foundation.org>,
Linus Walleij <linus.walleij@...ricsson.com>,
Chris Ball <cjb@...top.org>,
Russell King <linux@....linux.org.uk>
Subject: [PATCH] mmci: handle clock frequency 0 properly
This removes the default clocking for the MMCI controller so that
the external MCI card clock does not activate until the first
.set_ios() call is issued. It will further handle the transitions
from a clock != 0 to 0 and vice versa by gating/ungating the
clock with clk_disable()/clk_enable().
This assures that the MCI clock will not be active unless there
is a card in the MMC slot.
By default the MMC core will not gate off the clock to a card
once it's enabled, but with the separate patch for aggressive
clocking this can optionally be enabled for the system.
Cc: Chris Ball <cjb@...top.org>
Cc: Russell King <linux@....linux.org.uk>
Signed-off-by: Linus Walleij <linus.walleij@...ricsson.com>
---
Changes since v8:
The frequency registers shall be set with mmci_set_clkreg()
no matter whether the clock gets enabled or disabled, systems
without a clk framework will need this so that the clock
dividers are set to the apropriate values for clock 0 as
well, and that will probably mitigate power consumption
somewhat on these systems.
Chris: this is a new version after Russell found an error in
it. Can you please take the old version of this patch out of
the MMC tree so I can merge it through Russells ARM tree
instead? The patches are perfectly orthogonal so it doesn't
need to live in the MMC tree.
---
drivers/mmc/host/mmci.c | 33 ++++++++++++++++++++++-----------
drivers/mmc/host/mmci.h | 1 +
2 files changed, 23 insertions(+), 11 deletions(-)
diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index 0814b88..3709ab3 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -689,6 +689,22 @@ static void mmci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
mmci_set_clkreg(host, ios->clock);
+ /*
+ * Turn on clock whenever ios->clock transitions
+ * from 0 to !=0 and gate it off whenever ios->clock
+ * transitions from !=0 to 0.
+ */
+ if (host->iosclock == 0 && ios->clock != 0) {
+ dev_dbg(mmc_dev(mmc), "enable clock f=%d\n", ios->clock);
+ clk_enable(host->clk);
+ } else if (host->iosclock != 0 && ios->clock == 0) {
+ dev_dbg(mmc_dev(mmc), "disable clock\n");
+ clk_disable(host->clk);
+ } else if (ios->clock != 0) {
+ dev_dbg(mmc_dev(mmc), "set clock f=%d\n", ios->clock);
+ }
+ host->iosclock = ios->clock;
+
if (host->pwr != pwr) {
host->pwr = pwr;
writel(pwr, host->base + MMCIPOWER);
@@ -772,6 +788,8 @@ static int __devinit mmci_probe(struct amba_device *dev, struct amba_id *id)
host = mmc_priv(mmc);
host->mmc = mmc;
+ host->plat = plat;
+ host->variant = variant;
host->gpio_wp = -ENOSYS;
host->gpio_cd = -ENOSYS;
@@ -782,19 +800,14 @@ static int __devinit mmci_probe(struct amba_device *dev, struct amba_id *id)
dev_dbg(mmc_dev(mmc), "designer ID = 0x%02x\n", host->hw_designer);
dev_dbg(mmc_dev(mmc), "revision = 0x%01x\n", host->hw_revision);
+ /* This clock will be enabled/disabled by set_ios() calls later */
host->clk = clk_get(&dev->dev, NULL);
if (IS_ERR(host->clk)) {
ret = PTR_ERR(host->clk);
host->clk = NULL;
goto host_free;
}
-
- ret = clk_enable(host->clk);
- if (ret)
- goto clk_free;
-
- host->plat = plat;
- host->variant = variant;
+ host->iosclock = 0;
host->mclk = clk_get_rate(host->clk);
/*
* According to the spec, mclk is max 100 MHz,
@@ -804,7 +817,7 @@ static int __devinit mmci_probe(struct amba_device *dev, struct amba_id *id)
if (host->mclk > 100000000) {
ret = clk_set_rate(host->clk, 100000000);
if (ret < 0)
- goto clk_disable;
+ goto clk_free;
host->mclk = clk_get_rate(host->clk);
dev_dbg(mmc_dev(mmc), "eventual mclk rate: %u Hz\n",
host->mclk);
@@ -812,7 +825,7 @@ static int __devinit mmci_probe(struct amba_device *dev, struct amba_id *id)
host->base = ioremap(dev->res.start, resource_size(&dev->res));
if (!host->base) {
ret = -ENOMEM;
- goto clk_disable;
+ goto clk_free;
}
mmc->ops = &mmci_ops;
@@ -961,8 +974,6 @@ static int __devinit mmci_probe(struct amba_device *dev, struct amba_id *id)
gpio_free(host->gpio_cd);
err_gpio_cd:
iounmap(host->base);
- clk_disable:
- clk_disable(host->clk);
clk_free:
clk_put(host->clk);
host_free:
diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
index df06f01..4791a2b 100644
--- a/drivers/mmc/host/mmci.h
+++ b/drivers/mmc/host/mmci.h
@@ -167,6 +167,7 @@ struct mmci_host {
unsigned int mclk;
unsigned int cclk;
+ unsigned int iosclock;
u32 pwr;
struct mmci_platform_data *plat;
struct variant_data *variant;
--
1.6.3.3
--
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