>From 64b1814102b52c8b354d75e58b2ffb12119eb54d Mon Sep 17 00:00:00 2001
From: Philip Rakity <prakity@xxxxxxxxxxx>
Date: Mon, 20 Dec 2010 15:27:29 -0800
Subject: [PATCH] mmc: add support for H/W clock gating of SD controller
This code extends software clock gating in the MMC layer by adding the ability
to indicate that the SD controller supports hardware clock gating.
Hardware clock gating is enabled by setting the MMC capability
MMC_CAP_HW_CLOCK_GATING in the SD driver.
eg: host->mmc->caps |= MMC_CAP_HW_CLOCK_GATING
The approach follows the suggestion of Nico Pitre.
SD/MMC/eMMC cards use dynamic clocks
SDIO uses continuous clocks to properly detect SDIO card interrupts
The code has been tested using marvell linux for MMP2. The Marvell
controller support H/W clock gating.
Signed-off-by: Philip Rakity <prakity@xxxxxxxxxxx>
Signed-off-by: Mark F. Brown <markb@xxxxxxxxxxx>
---
drivers/mmc/core/core.c | 33 +++++++++++++++++++++++++++++++++
drivers/mmc/core/core.h | 13 +++++++++++++
drivers/mmc/core/host.c | 17 ++++++++++++++++-
include/linux/mmc/host.h | 1 +
4 files changed, 63 insertions(+), 1 deletions(-)
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index a8e89f3..259bd0d 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -683,10 +683,35 @@ void mmc_ungate_clock(struct mmc_host *host)
}
}
+/*
+ * Let hardware automatically gate the clock when the card becomes idle
+ */
+void mmc_hwgate_clock(struct mmc_host *host)
+{
+ if (host->caps & MMC_CAP_HW_CLOCK_GATING) {
+ host->clk_gated = true;
+ mmc_set_ios(host);
+ }
+}
+
+/*
+ * This ungates the clock by turning off h/w gating
+ */
+void mmc_hwungate_clock(struct mmc_host *host)
+{
+ if (host->caps & MMC_CAP_HW_CLOCK_GATING) {
+ host->clk_gated = false;
+ mmc_set_ios(host);
+ }
+}
+
+
void mmc_set_ungated(struct mmc_host *host)
{
unsigned long flags;
+ if (host->caps & MMC_CAP_HW_CLOCK_GATING)
+ return;
/*
* We've been given a new frequency while the clock is gated,
* so make sure we regard this as ungating it.
@@ -1553,6 +1578,7 @@ void mmc_rescan(struct work_struct *work)
mmc_hostname(host), __func__, host->f_init);
#endif
mmc_power_up(host);
+ mmc_hwungate_clock(host);
sdio_reset(host);
mmc_go_idle(host);
@@ -1577,6 +1603,9 @@ void mmc_rescan(struct work_struct *work)
if (mmc_send_app_op_cond(host, 0, &ocr))
goto out_fail;
+ /* hw clock gating is off when we get here */
+ /* do not enable clock gating for sdio cards */
+ /* sdio cards can miss interrupts */
if (mmc_attach_sd(host, ocr))
mmc_power_off(host);
}
@@ -1590,6 +1619,8 @@ void mmc_rescan(struct work_struct *work)
if (!err) {
if (mmc_attach_sd(host, ocr))
mmc_power_off(host);
+ else
+ mmc_hwgate_clock(host);
goto out;
}
@@ -1600,6 +1631,8 @@ void mmc_rescan(struct work_struct *work)
if (!err) {
if (mmc_attach_mmc(host, ocr))
mmc_power_off(host);
+ else
+ mmc_hwgate_clock(host);
goto out;
}
diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
index 026c975..3810e28 100644
--- a/drivers/mmc/core/core.h
+++ b/drivers/mmc/core/core.h
@@ -35,6 +35,19 @@ void mmc_set_chip_select(struct mmc_host *host, int mode);
void mmc_set_clock(struct mmc_host *host, unsigned int hz);
void mmc_gate_clock(struct mmc_host *host);
void mmc_ungate_clock(struct mmc_host *host);
+
+#ifdef CONFIG_MMC_CLKGATE
+void mmc_hwgate_clock(struct mmc_host *host);
+void mmc_hwungate_clock(struct mmc_host *host);
+#else
+static inline void mmc_hwgate_clock(struct mmc_host *host)
+{
+}
+
+static inline void mmc_hwungate_clock(struct mmc_host *host)
+{
+}
+#endif
void mmc_set_ungated(struct mmc_host *host);
void mmc_set_bus_mode(struct mmc_host *host, unsigned int mode);
void mmc_set_bus_width(struct mmc_host *host, unsigned int width);
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 92e3370..eebabde 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -130,6 +130,9 @@ void mmc_host_clk_ungate(struct mmc_host *host)
{
unsigned long flags;
+ if (host->caps & MMC_CAP_HW_CLOCK_GATING)
+ return;
+
mutex_lock(&host->clk_gate_mutex);
spin_lock_irqsave(&host->clk_lock, flags);
if (host->clk_gated) {
@@ -178,6 +181,9 @@ void mmc_host_clk_gate(struct mmc_host *host)
{
unsigned long flags;
+ if (host->caps & MMC_CAP_HW_CLOCK_GATING)
+ return;
+
spin_lock_irqsave(&host->clk_lock, flags);
host->clk_requests--;
if (mmc_host_may_gate_card(host->card) &&
@@ -198,7 +204,10 @@ unsigned int mmc_host_clk_rate(struct mmc_host *host)
unsigned long flags;
spin_lock_irqsave(&host->clk_lock, flags);
- if (host->clk_gated)
+ freq = host->ios.clock;
+ if (host->caps & MMC_CAP_HW_CLOCK_GATING)
+ freq = host->ios.clock;
+ else if (host->clk_gated)
freq = host->clk_old;
else
freq = host->ios.clock;
@@ -212,6 +221,9 @@ unsigned int mmc_host_clk_rate(struct mmc_host *host)
*/
static inline void mmc_host_clk_init(struct mmc_host *host)
{
+ if (host->caps & MMC_CAP_HW_CLOCK_GATING)
+ return;
+
host->clk_requests = 0;
/* Hold MCI clock for 8 cycles by default */
host->clk_delay = 8;
@@ -227,6 +239,9 @@ static inline void mmc_host_clk_init(struct mmc_host *host)
*/
static inline void mmc_host_clk_exit(struct mmc_host *host)
{
+ if (host->caps & MMC_CAP_HW_CLOCK_GATING)
+ return;
+
/*
* Wait for any outstanding gate and then make sure we're
* ungated before exiting.
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index bcb793e..4e4baff 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -173,6 +173,7 @@ struct mmc_host {
/* DDR mode at 1.2V */
#define MMC_CAP_POWER_OFF_CARD (1 << 13) /* Can power off after boot */
#define MMC_CAP_BUS_WIDTH_TEST (1 << 14) /* CMD14/CMD19 bus width ok */
+#define MMC_CAP_HW_CLOCK_GATING (1 << 15) /* h/w supports clock gating */
mmc_pm_flag_t pm_caps; /* supported pm features */
--
1.6.0.4
Attachment:
0018-mmc-add-support-for-H-W-clock-gating-of-SD-controll.patch
Description: 0018-mmc-add-support-for-H-W-clock-gating-of-SD-controll.patch
