[PATCH v8 1/5] PM / Runtime: Add getter for querying the IRQ safe option

[Krzysztof Kozlowski]

Add a simple getter pm_runtime_is_irq_safe() for querying whether runtime
PM IRQ safe was set or not.

Various bus drivers implementing runtime PM may use choose to suspend
differently based on IRQ safeness status of child driver (e.g. do not
unprepare the clock if IRQ safe is not set).

Signed-off-by: Krzysztof Kozlowski <***@samsung.com>
Reviewed-by: Ulf Hansson <***@linaro.org>
---
Documentation/power/runtime_pm.txt | 4 ++++
include/linux/pm_runtime.h | 6 ++++++
2 files changed, 10 insertions(+)

diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index f32ce5419573..397b81593142 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -468,6 +468,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
- set the power.irq_safe flag for the device, causing the runtime-PM
callbacks to be invoked with interrupts off

+ bool pm_runtime_is_irq_safe(struct device *dev);
+ - return true if power.irq_safe flag was set for the device, causing
+ the runtime-PM callbacks to be invoked with interrupts off
+
void pm_runtime_mark_last_busy(struct device *dev);
- set the power.last_busy field to the current time

diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
index 367f49b9a1c9..44d74f0f182e 100644
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -128,6 +128,11 @@ static inline void pm_runtime_mark_last_busy(struct device *dev)
ACCESS_ONCE(dev->power.last_busy) = jiffies;
}

+static inline bool pm_runtime_is_irq_safe(struct device *dev)
+{
+ return dev->power.irq_safe;
+}
+
#else /* !CONFIG_PM_RUNTIME */

static inline int __pm_runtime_idle(struct device *dev, int rpmflags)
@@ -167,6 +172,7 @@ static inline bool pm_runtime_enabled(struct device *dev) { return false; }

static inline void pm_runtime_no_callbacks(struct device *dev) {}
static inline void pm_runtime_irq_safe(struct device *dev) {}
+static inline bool pm_runtime_is_irq_safe(struct device *dev) { return false; }

static inline bool pm_runtime_callbacks_present(struct device *dev) { return false; }
static inline void pm_runtime_mark_last_busy(struct device *dev) {}

[Krzysztof Kozlowski]

Add amba_pclk_prepare() and amba_pclk_unprepare() inline functions for
handling the AMBA bus clock by device drivers.

Signed-off-by: Krzysztof Kozlowski <***@samsung.com>
---
include/linux/amba/bus.h | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h
index c324f5700d1a..ac02f9bd63dc 100644
--- a/include/linux/amba/bus.h
+++ b/include/linux/amba/bus.h
@@ -97,6 +97,16 @@ void amba_release_regions(struct amba_device *);
#define amba_pclk_disable(d) \
do { if (!IS_ERR((d)->pclk)) clk_disable((d)->pclk); } while (0)

+static inline int amba_pclk_prepare(struct amba_device *dev)
+{
+ return clk_prepare(dev->pclk);
+}
+
+static inline void amba_pclk_unprepare(struct amba_device *dev)
+{
+ clk_unprepare(dev->pclk);
+}
+
/* Some drivers don't use the struct amba_device */
#define AMBA_CONFIG_BITS(a) (((a) >> 24) & 0xff)
#define AMBA_REV_BITS(a) (((a) >> 20) & 0x0f)

[Krzysztof Kozlowski]

The AMBA bus driver defines runtime Power Management functions which
disable and unprepare AMBA bus clock. This is problematic for runtime PM
because unpreparing a clock might sleep so it is not interrupt safe.

However some drivers may want to implement runtime PM functions in
interrupt-safe way (see pm_runtime_irq_safe()). In such case the AMBA
bus driver should only disable/enable the clock in runtime suspend and
resume callbacks.

Detect the device driver behavior after calling its probe function and
store it. During runtime suspend/resume deal with clocks according to
stored value.

Signed-off-by: Krzysztof Kozlowski <***@samsung.com>
Reviewed-by: Ulf Hansson <***@linaro.org>
---
drivers/amba/bus.c | 29 +++++++++++++++++++++++++----
include/linux/amba/bus.h | 1 +
2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c
index 47bbdc1b5be3..474434e1b1b9 100644
--- a/drivers/amba/bus.c
+++ b/drivers/amba/bus.c
@@ -95,8 +95,18 @@ static int amba_pm_runtime_suspend(struct device *dev)
struct amba_device *pcdev = to_amba_device(dev);
int ret = pm_generic_runtime_suspend(dev);

- if (ret == 0 && dev->driver)
- clk_disable_unprepare(pcdev->pclk);
+ if (ret == 0 && dev->driver) {
+ /*
+ * Drivers should not change pm_runtime_irq_safe()
+ * after probe.
+ */
+ WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev));
+
+ if (pcdev->irq_safe)
+ clk_disable(pcdev->pclk);
+ else
+ clk_disable_unprepare(pcdev->pclk);
+ }

return ret;
}
@@ -107,7 +117,16 @@ static int amba_pm_runtime_resume(struct device *dev)
int ret;

if (dev->driver) {
- ret = clk_prepare_enable(pcdev->pclk);
+ /*
+ * Drivers should not change pm_runtime_irq_safe()
+ * after probe.
+ */
+ WARN_ON(pcdev->irq_safe != pm_runtime_is_irq_safe(dev));
+
+ if (pcdev->irq_safe)
+ ret = clk_enable(pcdev->pclk);
+ else
+ ret = clk_prepare_enable(pcdev->pclk);
/* Failure is probably fatal to the system, but... */
if (ret)
return ret;
@@ -198,8 +217,10 @@ static int amba_probe(struct device *dev)
pm_runtime_enable(dev);

ret = pcdrv->probe(pcdev, id);
- if (ret == 0)
+ if (ret == 0) {
+ pcdev->irq_safe = pm_runtime_is_irq_safe(dev);
break;
+ }

pm_runtime_disable(dev);
pm_runtime_set_suspended(dev);
diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h
index ac02f9bd63dc..c4bae79851fb 100644
--- a/include/linux/amba/bus.h
+++ b/include/linux/amba/bus.h
@@ -32,6 +32,7 @@ struct amba_device {
struct clk *pclk;
unsigned int periphid;
unsigned int irq[AMBA_NR_IRQS];
+ unsigned int irq_safe:1;
};

struct amba_driver {

[Krzysztof Kozlowski]

This patch adds both normal PM suspend/resume support and runtime PM
support to pl330 DMA engine driver.

The runtime power management for pl330 DMA driver allows gating of AMBA
clock (PDMA) in FSYS clock domain, when the device is not processing any
requests. This is necessary to enter low power modes on Exynos SoCs
(e.g. LPA on Exynos4x12 or W-AFTR on Exynos3250).

Runtime PM resuming of the device may happen in atomic context (during
call device_issue_pending()) so pm_runtime_irq_safe() is used. This will
lead only to disabling/enabling of the clock but this is sufficient for
gating the clock and for reducing energy usage.

During system sleep the AMBA bus clock is also unprepared.

Suggested-by: Bartlomiej Zolnierkiewicz <***@samsung.com>
Signed-off-by: Krzysztof Kozlowski <***@samsung.com>
Reviewed-by: Ulf Hansson <***@linaro.org>
---
drivers/dma/pl330.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 90 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 4839bfa74a10..b123431e62ed 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -27,6 +27,7 @@
#include <linux/of.h>
#include <linux/of_dma.h>
#include <linux/err.h>
+#include <linux/pm_runtime.h>

#include "dmaengine.h"
#define PL330_MAX_CHAN 8
@@ -265,6 +266,9 @@ static unsigned cmd_line;

#define NR_DEFAULT_DESC 16

+/* Delay for runtime PM autosuspend, ms */
+#define PL330_AUTOSUSPEND_DELAY 20
+
/* Populated by the PL330 core driver for DMA API driver's info */
struct pl330_config {
u32 periph_id;
@@ -1958,6 +1962,7 @@ static void pl330_tasklet(unsigned long data)
struct dma_pl330_chan *pch = (struct dma_pl330_chan *)data;
struct dma_pl330_desc *desc, *_dt;
unsigned long flags;
+ bool power_down = false;

spin_lock_irqsave(&pch->lock, flags);

@@ -1972,10 +1977,17 @@ static void pl330_tasklet(unsigned long data)
/* Try to submit a req imm. next to the last completed cookie */
fill_queue(pch);

- /* Make sure the PL330 Channel thread is active */
- spin_lock(&pch->thread->dmac->lock);
- _start(pch->thread);
- spin_unlock(&pch->thread->dmac->lock);
+ if (list_empty(&pch->work_list)) {
+ spin_lock(&pch->thread->dmac->lock);
+ _stop(pch->thread);
+ spin_unlock(&pch->thread->dmac->lock);
+ power_down = true;
+ } else {
+ /* Make sure the PL330 Channel thread is active */
+ spin_lock(&pch->thread->dmac->lock);
+ _start(pch->thread);
+ spin_unlock(&pch->thread->dmac->lock);
+ }

while (!list_empty(&pch->completed_list)) {
dma_async_tx_callback callback;
@@ -1990,6 +2002,12 @@ static void pl330_tasklet(unsigned long data)
if (pch->cyclic) {
desc->status = PREP;
list_move_tail(&desc->node, &pch->work_list);
+ if (power_down) {
+ spin_lock(&pch->thread->dmac->lock);
+ _start(pch->thread);
+ spin_unlock(&pch->thread->dmac->lock);
+ power_down = false;
+ }
} else {
desc->status = FREE;
list_move_tail(&desc->node, &pch->dmac->desc_pool);
@@ -2004,6 +2022,12 @@ static void pl330_tasklet(unsigned long data)
}
}
spin_unlock_irqrestore(&pch->lock, flags);
+
+ /* If work list empty, power down */
+ if (power_down) {
+ pm_runtime_mark_last_busy(pch->dmac->ddma.dev);
+ pm_runtime_put_autosuspend(pch->dmac->ddma.dev);
+ }
}

bool pl330_filter(struct dma_chan *chan, void *param)
@@ -2073,6 +2097,7 @@ static int pl330_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd, unsigned

switch (cmd) {
case DMA_TERMINATE_ALL:
+ pm_runtime_get_sync(pl330->ddma.dev);
spin_lock_irqsave(&pch->lock, flags);

spin_lock(&pl330->lock);
@@ -2099,10 +2124,15 @@ static int pl330_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd, unsigned
dma_cookie_complete(&desc->txd);
}

+ if (!list_empty(&pch->work_list))
+ pm_runtime_put(pl330->ddma.dev);
+
list_splice_tail_init(&pch->submitted_list, &pl330->desc_pool);
list_splice_tail_init(&pch->work_list, &pl330->desc_pool);
list_splice_tail_init(&pch->completed_list, &pl330->desc_pool);
spin_unlock_irqrestore(&pch->lock, flags);
+ pm_runtime_mark_last_busy(pl330->ddma.dev);
+ pm_runtime_put_autosuspend(pl330->ddma.dev);
break;
case DMA_SLAVE_CONFIG:
slave_config = (struct dma_slave_config *)arg;
@@ -2138,6 +2168,7 @@ static void pl330_free_chan_resources(struct dma_chan *chan)

tasklet_kill(&pch->task);

+ pm_runtime_get_sync(pch->dmac->ddma.dev);
spin_lock_irqsave(&pch->lock, flags);

pl330_release_channel(pch->thread);
@@ -2147,6 +2178,8 @@ static void pl330_free_chan_resources(struct dma_chan *chan)
list_splice_tail_init(&pch->work_list, &pch->dmac->desc_pool);

spin_unlock_irqrestore(&pch->lock, flags);
+ pm_runtime_mark_last_busy(pch->dmac->ddma.dev);
+ pm_runtime_put_autosuspend(pch->dmac->ddma.dev);
}

static enum dma_status
@@ -2162,6 +2195,15 @@ static void pl330_issue_pending(struct dma_chan *chan)
unsigned long flags;

spin_lock_irqsave(&pch->lock, flags);
+ if (list_empty(&pch->work_list)) {
+ /*
+ * Warn on nothing pending. Empty submitted_list may
+ * break our pm_runtime usage counter as it is
+ * updated on work_list emptiness status.
+ */
+ WARN_ON(list_empty(&pch->submitted_list));
+ pm_runtime_get_sync(pch->dmac->ddma.dev);
+ }
list_splice_tail_init(&pch->submitted_list, &pch->work_list);
spin_unlock_irqrestore(&pch->lock, flags);

@@ -2585,6 +2627,41 @@ static int pl330_dma_device_slave_caps(struct dma_chan *dchan,
return 0;
}

+/*
+ * Assume that IRQ safe runtime PM is chosen in probe and amba bus driver
+ * will only disable/enable the clock in runtime PM suspend/resume.
+ */
+static int __maybe_unused pl330_suspend(struct device *dev)
+{
+ struct amba_device *pcdev = to_amba_device(dev);
+ int ret;
+
+ ret = pm_runtime_force_suspend(dev);
+ if (ret)
+ return ret;
+
+ amba_pclk_unprepare(pcdev);
+
+ return 0;
+}
+
+static int __maybe_unused pl330_resume(struct device *dev)
+{
+ struct amba_device *pcdev = to_amba_device(dev);
+
+ amba_pclk_prepare(pcdev);
+
+ /*
+ * TODO: Idea for future. The device should not be woken up after
+ * system resume if it is not needed. It could stay runtime suspended
+ * waiting for DMA requests. However for safe suspend and resume we
+ * forcibly resume the device here.
+ */
+ return pm_runtime_force_resume(dev);
+}
+
+static SIMPLE_DEV_PM_OPS(pl330_pm, pl330_suspend, pl330_resume);
+
static int
pl330_probe(struct amba_device *adev, const struct amba_id *id)
{
@@ -2738,6 +2815,12 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
pcfg->data_buf_dep, pcfg->data_bus_width / 8, pcfg->num_chan,
pcfg->num_peri, pcfg->num_events);

+ pm_runtime_irq_safe(&adev->dev);
+ pm_runtime_use_autosuspend(&adev->dev);
+ pm_runtime_set_autosuspend_delay(&adev->dev, PL330_AUTOSUSPEND_DELAY);
+ pm_runtime_mark_last_busy(&adev->dev);
+ pm_runtime_put_autosuspend(&adev->dev);
+
return 0;
probe_err3:
/* Idle the DMAC */
@@ -2764,6 +2847,8 @@ static int pl330_remove(struct amba_device *adev)
struct pl330_dmac *pl330 = amba_get_drvdata(adev);
struct dma_pl330_chan *pch, *_p;

+ pm_runtime_get_noresume(pl330->ddma.dev);
+
if (adev->dev.of_node)
of_dma_controller_free(adev->dev.of_node);

@@ -2802,6 +2887,7 @@ static struct amba_driver pl330_driver = {
.drv = {
.owner = THIS_MODULE,
.name = "dma-pl330",
+ .pm = &pl330_pm,
},
.id_table = pl330_ids,
.probe = pl330_probe,

[Krzysztof Kozlowski]

Remove the amba_pclk_enable and amba_pclk_disable macros because they
are not used by the drivers.

Signed-off-by: Krzysztof Kozlowski <***@samsung.com>
Reviewed-by: Ulf Hansson <***@linaro.org>
---
include/linux/amba/bus.h | 6 ------
1 file changed, 6 deletions(-)

diff --git a/include/linux/amba/bus.h b/include/linux/amba/bus.h
index c4bae79851fb..566adf0e0412 100644
--- a/include/linux/amba/bus.h
+++ b/include/linux/amba/bus.h
@@ -92,12 +92,6 @@ struct amba_device *amba_find_device(const char *, struct device *, unsigned int
int amba_request_regions(struct amba_device *, const char *);
void amba_release_regions(struct amba_device *);

-#define amba_pclk_enable(d) \
- (IS_ERR((d)->pclk) ? 0 : clk_enable((d)->pclk))
-
-#define amba_pclk_disable(d) \
- do { if (!IS_ERR((d)->pclk)) clk_disable((d)->pclk); } while (0)
-
static inline int amba_pclk_prepare(struct amba_device *dev)
{
return clk_prepare(dev->pclk);