Re: [PATCH v7 4/5] dma: pl330: add Power Management support

[Krzysztof Kozlowski <k.kozlowski@samsung.com>]

On śro, 2014-10-15 at 09:19 +0200, Ulf Hansson wrote:
> On 24 September 2014 15:50, Krzysztof Kozlowski <k.kozlowski@samsung.com> wrote:
> > 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 <b.zolnierkie@samsung.com>
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> 
> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>

Thanks for review!

You pointed one issue with patch 2/5 off-the-list. I'll wait for merge
window to end, fix it and re-send.

Best regards,
Krzysztof


> 
> Kind regards
> Uffe
> 
> > ---
> >  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,
> > --
> > 1.9.1
> >