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Date: Wed, 28 Jan 2015 10:35:24 +1100
From: NeilBrown <neilb@...e.de>
To: Tony Lindgren <tony@...mide.com>,
Ulf Hansson <ulf.hansson@...aro.org>
Cc: Andreas Fenkart <afenkart@...il.com>, linux-mmc@...r.kernel.org,
linux-kernel@...r.kernel.org,
GTA04 owners <gta04-owner@...delico.com>,
NeilBrown <neil@...wn.name>, linux-omap@...r.kernel.org
Subject: [PATCH 3/3] mmc: omap_hsmmc: switch to 1-bit before turning off
clocks if interrupts expected.
According to section 7.1.2 of
http://www.sandisk.com/media/File/OEM/Manuals/SD_SDIO_specsv1.pdf
In the case where the interrupt mechanism is used to wake the host while
the card is in a low power state (i.e. no clocks), Both the card and the
host shall be placed into the 1-bit SD mode prior to stopping the clock.
This is particularly important for the Marvell "libertas" wifi chip
in the GTA04. While in 4-bit mode it will only signal an interrupt
when the clock is running (which is why setting CLKEXTFREE is
important).
In 1-bit mode, the interrupt is asynchronous (explained in OMAP3
TRM description of the CIRQ flag to MMCHS_STAT:
In 1-bit mode, interrupt source is asynchronous (can be a source of
asynchronous wakeup).
In 4-bit mode, interrupt source is sampled during the interrupt
cycle.
)
We cannot simply set 1-bit mode in omap_hsmmc_runtime_suspend
as that is called under a spinlock, and setting 1-bit mode requires
a sleeping call to the card.
So:
- use a work_struct to schedule setting of 1-bit mode
- intro a 'force_narrow' state flag which transitions:
0 -> NARROW_PENDING -> NARROW_FORCED -> 0
- have omap_hsmmc_runtime_suspend fail if interrupts are expected
but bus is not in 1-bit mode. When it fails it schedules
the work to change the width. and sets NARROW_PENDING
- when the host is claimed, if NARROW_FORCED is set, restore the
4-bit bus
- When the host is released (disable_fclk), if NARROW_FORCED,
then suspend immediately, no autosuspend. If NARROW_PENDING,
clear that flag as the device has obviously just been used.
This all allows a graceful and race-free switch to 1-bit mode
before switching off the clocks, if interrupts are enabled.
With this, I can use my libertas wifi with a 4-bit bus, with
interrupts and runtime power-management enabled, and get around
14Mb/sec throughput (which is the best I've seen).
Signed-off-by: NeilBrown <neil@...wn.name>
---
drivers/mmc/host/omap_hsmmc.c | 55 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 53 insertions(+), 2 deletions(-)
diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index f84cfb01716d..91ddebbec8a3 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -214,6 +214,10 @@ struct omap_hsmmc_host {
int reqs_blocked;
int use_reg;
int req_in_progress;
+ int force_narrow;
+#define NARROW_PENDING 1
+#define NARROW_FORCED 2
+ struct work_struct width_work;
unsigned long clk_rate;
unsigned int flags;
#define AUTO_CMD23 (1 << 0) /* Auto CMD23 support */
@@ -1778,12 +1782,43 @@ static void omap_hsmmc_conf_bus_power(struct omap_hsmmc_host *host)
set_sd_bus_power(host);
}
+static void omap_hsmmc_width_work(struct work_struct *work)
+{
+ struct omap_hsmmc_host *host = container_of(work,
+ struct omap_hsmmc_host,
+ width_work);
+ atomic_t noblock;
+
+ atomic_set(&noblock, 1);
+ if (__mmc_claim_host(host->mmc, &noblock)) {
+ /* Device active again */
+ host->force_narrow = 0;
+ return;
+ }
+ if (host->force_narrow != NARROW_PENDING) {
+ /* Someone claimed and released before we got here */
+ mmc_release_host(host->mmc);
+ return;
+ }
+ if (sdio_disable_wide(host->mmc->card) == 0)
+ host->force_narrow = NARROW_FORCED;
+ else
+ host->force_narrow = 0;
+ mmc_release_host(host->mmc);
+}
+
static int omap_hsmmc_enable_fclk(struct mmc_host *mmc)
{
struct omap_hsmmc_host *host = mmc_priv(mmc);
pm_runtime_get_sync(host->dev);
+ if (host->force_narrow == NARROW_FORCED) {
+ if (sdio_enable_4bit_bus(mmc->card) > 0)
+ mmc_set_bus_width(mmc, MMC_BUS_WIDTH_4);
+ host->force_narrow = 0;
+ }
+
return 0;
}
@@ -1791,8 +1826,13 @@ static int omap_hsmmc_disable_fclk(struct mmc_host *mmc)
{
struct omap_hsmmc_host *host = mmc_priv(mmc);
- pm_runtime_mark_last_busy(host->dev);
- pm_runtime_put_autosuspend(host->dev);
+ if (host->force_narrow == NARROW_FORCED) {
+ pm_runtime_put_sync(host->dev);
+ } else {
+ host->force_narrow = 0;
+ pm_runtime_mark_last_busy(host->dev);
+ pm_runtime_put_autosuspend(host->dev);
+ }
return 0;
}
@@ -2024,6 +2064,7 @@ static int omap_hsmmc_probe(struct platform_device *pdev)
host->power_mode = MMC_POWER_OFF;
host->next_data.cookie = 1;
host->pbias_enabled = 0;
+ INIT_WORK(&host->width_work, omap_hsmmc_width_work);
ret = omap_hsmmc_gpio_init(mmc, host, pdata);
if (ret)
@@ -2311,6 +2352,16 @@ static int omap_hsmmc_runtime_suspend(struct device *dev)
spin_lock_irqsave(&host->irq_lock, flags);
if ((host->mmc->caps & MMC_CAP_SDIO_IRQ) &&
(host->flags & HSMMC_SDIO_IRQ_ENABLED)) {
+ if (host->mmc->ios.bus_width != MMC_BUS_WIDTH_1) {
+ /* In 4-bit mode the card need the clock
+ * to deliver interrupts, so it isn't safe
+ * to turn it off.
+ */
+ host->force_narrow = NARROW_PENDING;
+ schedule_work(&host->width_work);
+ ret = -EBUSY;
+ goto abort;
+ }
/* disable sdio irq handling to prevent race */
OMAP_HSMMC_WRITE(host->base, ISE, 0);
OMAP_HSMMC_WRITE(host->base, IE, 0);
--
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