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Subject[PATCH 2/3] dmaengine: at_hdmac: improve power management routines
Date
Save/restore dma controller state across a suspend-resume sequence.
The prepare() function will wait for the non-cyclic channels to become idle.
It also deals with cyclic operations with the start at next period while
resuming.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
drivers/dma/at_hdmac.c | 88 ++++++++++++++++++++++++++++++++++++++++++-
drivers/dma/at_hdmac_regs.h | 7 +++
2 files changed, 94 insertions(+), 1 deletions(-)
diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index fd87b96..7096adb 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -1385,27 +1385,113 @@ static void at_dma_shutdown(struct platform_device *pdev)
clk_disable(atdma->clk);
}

+static int at_dma_prepare(struct device *dev)
+{
+ struct platform_device *pdev = to_platform_device(dev);
+ struct at_dma *atdma = platform_get_drvdata(pdev);
+ struct dma_chan *chan, *_chan;
+
+ list_for_each_entry_safe(chan, _chan, &atdma->dma_common.channels,
+ device_node) {
+ struct at_dma_chan *atchan = to_at_dma_chan(chan);
+ /* wait for transaction completion (except in cyclic case) */
+ if (atc_chan_is_enabled(atchan) &&
+ !test_bit(ATC_IS_CYCLIC, &atchan->status))
+ return -EAGAIN;
+ }
+ return 0;
+}
+
+static void atc_suspend_cyclic(struct at_dma_chan *atchan)
+{
+ struct dma_chan *chan = &atchan->chan_common;
+
+ /* Channel should be paused by user
+ * do it anyway even if it is not done already */
+ if (!test_bit(ATC_IS_PAUSED, &atchan->status)) {
+ dev_warn(chan2dev(chan),
+ "cyclic channel not paused, should be done by channel user\n");
+ atc_control(chan, DMA_PAUSE, 0);
+ }
+
+ /* now preserve additional data for cyclic operations */
+ /* next descriptor address in the cyclic list */
+ atchan->save_dscr = channel_readl(atchan, DSCR);
+
+ vdbg_dump_regs(atchan);
+}
+
static int at_dma_suspend_noirq(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct at_dma *atdma = platform_get_drvdata(pdev);
+ struct dma_chan *chan, *_chan;

- at_dma_off(platform_get_drvdata(pdev));
+ /* preserve data */
+ list_for_each_entry_safe(chan, _chan, &atdma->dma_common.channels,
+ device_node) {
+ struct at_dma_chan *atchan = to_at_dma_chan(chan);
+
+ if (test_bit(ATC_IS_CYCLIC, &atchan->status))
+ atc_suspend_cyclic(atchan);
+ atchan->save_cfg = channel_readl(atchan, CFG);
+ }
+ atdma->save_imr = dma_readl(atdma, EBCIMR);
+
+ /* disable DMA controller */
+ at_dma_off(atdma);
clk_disable(atdma->clk);
return 0;
}

+static void atc_resume_cyclic(struct at_dma_chan *atchan)
+{
+ struct at_dma *atdma = to_at_dma(atchan->chan_common.device);
+
+ /* restore channel status for cyclic descriptors list:
+ * next descriptor in the cyclic list at the time of suspend */
+ channel_writel(atchan, SADDR, 0);
+ channel_writel(atchan, DADDR, 0);
+ channel_writel(atchan, CTRLA, 0);
+ channel_writel(atchan, CTRLB, 0);
+ channel_writel(atchan, DSCR, atchan->save_dscr);
+ dma_writel(atdma, CHER, atchan->mask);
+
+ /* channel pause status should be removed by channel user
+ * We cannot take the initiative to do it here */
+
+ vdbg_dump_regs(atchan);
+}
+
static int at_dma_resume_noirq(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct at_dma *atdma = platform_get_drvdata(pdev);
+ struct dma_chan *chan, *_chan;

+ /* bring back DMA controller */
clk_enable(atdma->clk);
dma_writel(atdma, EN, AT_DMA_ENABLE);
+
+ /* clear any pending interrupt */
+ while (dma_readl(atdma, EBCISR))
+ cpu_relax();
+
+ /* restore saved data */
+ dma_writel(atdma, EBCIER, atdma->save_imr);
+ list_for_each_entry_safe(chan, _chan, &atdma->dma_common.channels,
+ device_node) {
+ struct at_dma_chan *atchan = to_at_dma_chan(chan);
+
+ channel_writel(atchan, CFG, atchan->save_cfg);
+ if (test_bit(ATC_IS_CYCLIC, &atchan->status))
+ atc_resume_cyclic(atchan);
+ }
return 0;
}

static const struct dev_pm_ops at_dma_dev_pm_ops = {
+ .prepare = at_dma_prepare,
.suspend_noirq = at_dma_suspend_noirq,
.resume_noirq = at_dma_resume_noirq,
};
diff --git a/drivers/dma/at_hdmac_regs.h b/drivers/dma/at_hdmac_regs.h
index 087dbf1..6f0c4a3 100644
--- a/drivers/dma/at_hdmac_regs.h
+++ b/drivers/dma/at_hdmac_regs.h
@@ -204,6 +204,9 @@ enum atc_status {
* @status: transmit status information from irq/prep* functions
* to tasklet (use atomic operations)
* @tasklet: bottom half to finish transaction work
+ * @save_cfg: configuration register that is saved on suspend/resume cycle
+ * @save_dscr: for cyclic operations, preserve next descriptor address in
+ * the cyclic list on suspend/resume cycle
* @lock: serializes enqueue/dequeue operations to descriptors lists
* @completed_cookie: identifier for the most recently completed operation
* @active_list: list of descriptors dmaengine is being running on
@@ -218,6 +221,8 @@ struct at_dma_chan {
u8 mask;
unsigned long status;
struct tasklet_struct tasklet;
+ u32 save_cfg;
+ u32 save_dscr;

spinlock_t lock;

@@ -248,6 +253,7 @@ static inline struct at_dma_chan *to_at_dma_chan(struct dma_chan *dchan)
* @chan_common: common dmaengine dma_device object members
* @ch_regs: memory mapped register base
* @clk: dma controller clock
+ * @save_imr: interrupt mask register that is saved on suspend/resume cycle
* @all_chan_mask: all channels availlable in a mask
* @dma_desc_pool: base of DMA descriptor region (DMA address)
* @chan: channels table to store at_dma_chan structures
@@ -256,6 +262,7 @@ struct at_dma {
struct dma_device dma_common;
void __iomem *regs;
struct clk *clk;
+ u32 save_imr;

u8 all_chan_mask;

--
1.7.3
--
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