Messages in this thread | | | Date | Thu, 25 Aug 2011 16:55:03 +0200 (CEST) | From | Guennadi Liakhovetski <> | Subject | Re: [PATCH] dma: shdma: transfer based runtime PM |
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On Thu, 25 Aug 2011, Koul, Vinod wrote:
> On Thu, 2011-08-25 at 16:37 +0200, Guennadi Liakhovetski wrote: > > On Thu, 25 Aug 2011, Koul, Vinod wrote: > > > > > On Thu, 2011-08-18 at 16:55 +0200, Guennadi Liakhovetski wrote: > > > > Currently the shdma dmaengine driver uses runtime PM to save power, when > > > > no channel on the specific controller is requested by a user. This patch > > > > switches the driver to count individual DMA transfers. That way the > > > > controller can be powered down between transfers, even if some of its > > > > channels are in use. > > > No, I don't agree with the approach here, you don't need to count the > > > transfers, the runtime_pm framework does that very well for you. > > > > > > What you need to do is to call pm_runtime_get() in your .issue_pending > > > callback (NOT in tx_submit anyway, this needs to be fixed in driver, see > > > the Documentation/dmaengine.txt > > > And once the transfer has completed you need to call pm_rumtime_put() > > > > This has been discussed before: > > > > http://marc.info/?l=linux-sh&m=131004613801231&w=2 > uh, yes but at least the runtime_xxx needs to get fixed.
This isn't so easy either. In principle, yes, I know, that pm_runtime_* calls count depth. But I don't think the DMA case is simple enough for that. It's not necessarily one in - one out. Think about terminating transfers, timing out, closing the channel, etc. In those cases you'd have to count pending transfers and pm_runtime_put() for each of them. This is even less trivial on shdma, where DMA transfers get split into sg-lists, which are then all queued on a single queue. So, you'd have to scan that queue and check for transfer borders... That's why I decided that doing just one get() on the first descriptor and one put() on the last one would be easier and more robust.
Thanks Guennadi
> > -- > ~Vinod > > > > Thanks > > Guennadi > > > > > > > > Runtime PM framework actually counts the device usage count and whenever > > > your device usage count goes to 0 it will call .runtime_suspend > > > callback, thus enable you to save power. > > > > > > -- > > > ~Vinod > > > > > > > > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de> > > > > --- > > > > > > > > tested on mackerel (sh7372) with dmatest, sh_mobile_sdhi and sh_mmcif with > > > > runtime PM and STR. > > > > > > > > drivers/dma/shdma.c | 94 +++++++++++++++++++++++++++++++++++++-------------- > > > > drivers/dma/shdma.h | 7 ++++ > > > > 2 files changed, 75 insertions(+), 26 deletions(-) > > > > > > > > diff --git a/drivers/dma/shdma.c b/drivers/dma/shdma.c > > > > index e7bb747..81809c2 100644 > > > > --- a/drivers/dma/shdma.c > > > > +++ b/drivers/dma/shdma.c > > > > @@ -259,15 +259,23 @@ static int dmae_set_dmars(struct sh_dmae_chan *sh_chan, u16 val) > > > > return 0; > > > > } > > > > > > > > +static void sh_chan_xfer_ld_queue(struct sh_dmae_chan *sh_chan); > > > > + > > > > static dma_cookie_t sh_dmae_tx_submit(struct dma_async_tx_descriptor *tx) > > > > { > > > > struct sh_desc *desc = tx_to_sh_desc(tx), *chunk, *last = desc, *c; > > > > struct sh_dmae_chan *sh_chan = to_sh_chan(tx->chan); > > > > + struct sh_dmae_slave *param = tx->chan->private; > > > > dma_async_tx_callback callback = tx->callback; > > > > dma_cookie_t cookie; > > > > - unsigned long flags; > > > > + bool power_up; > > > > > > > > - spin_lock_irqsave(&sh_chan->desc_lock, flags); > > > > + spin_lock_irq(&sh_chan->desc_lock); > > > > + > > > > + if (list_empty(&sh_chan->ld_queue)) > > > > + power_up = true; > > > > + else > > > > + power_up = false; > > > > > > > > cookie = sh_chan->common.cookie; > > > > cookie++; > > > > @@ -303,7 +311,38 @@ static dma_cookie_t sh_dmae_tx_submit(struct dma_async_tx_descriptor *tx) > > > > tx->cookie, &last->async_tx, sh_chan->id, > > > > desc->hw.sar, desc->hw.tcr, desc->hw.dar); > > > > > > > > - spin_unlock_irqrestore(&sh_chan->desc_lock, flags); > > > > + if (power_up) { > > > > + sh_chan->pm_state = DMAE_PM_BUSY; > > > > + > > > > + pm_runtime_get(sh_chan->dev); > > > > + > > > > + spin_unlock_irq(&sh_chan->desc_lock); > > > > + > > > > + pm_runtime_barrier(sh_chan->dev); > > > > + > > > > + spin_lock_irq(&sh_chan->desc_lock); > > > > + > > > > + /* Have we been reset, while waiting? */ > > > > + if (sh_chan->pm_state != DMAE_PM_ESTABLISHED) { > > > > + dev_dbg(sh_chan->dev, "Bring up channel %d\n", > > > > + sh_chan->id); > > > > + if (param) { > > > > + const struct sh_dmae_slave_config *cfg = > > > > + param->config; > > > > + > > > > + dmae_set_dmars(sh_chan, cfg->mid_rid); > > > > + dmae_set_chcr(sh_chan, cfg->chcr); > > > > + } else { > > > > + dmae_init(sh_chan); > > > > + } > > > > + > > > > + if (sh_chan->pm_state == DMAE_PM_PENDING) > > > > + sh_chan_xfer_ld_queue(sh_chan); > > > > + sh_chan->pm_state = DMAE_PM_ESTABLISHED; > > > > + } > > > > + } > > > > + > > > > + spin_unlock_irq(&sh_chan->desc_lock); > > > > > > > > return cookie; > > > > } > > > > @@ -347,8 +386,6 @@ static int sh_dmae_alloc_chan_resources(struct dma_chan *chan) > > > > struct sh_dmae_slave *param = chan->private; > > > > int ret; > > > > > > > > - pm_runtime_get_sync(sh_chan->dev); > > > > - > > > > /* > > > > * This relies on the guarantee from dmaengine that alloc_chan_resources > > > > * never runs concurrently with itself or free_chan_resources. > > > > @@ -368,11 +405,6 @@ static int sh_dmae_alloc_chan_resources(struct dma_chan *chan) > > > > } > > > > > > > > param->config = cfg; > > > > - > > > > - dmae_set_dmars(sh_chan, cfg->mid_rid); > > > > - dmae_set_chcr(sh_chan, cfg->chcr); > > > > - } else { > > > > - dmae_init(sh_chan); > > > > } > > > > > > > > while (sh_chan->descs_allocated < NR_DESCS_PER_CHANNEL) { > > > > @@ -401,7 +433,6 @@ edescalloc: > > > > etestused: > > > > efindslave: > > > > chan->private = NULL; > > > > - pm_runtime_put(sh_chan->dev); > > > > return ret; > > > > } > > > > > > > > @@ -413,7 +444,6 @@ static void sh_dmae_free_chan_resources(struct dma_chan *chan) > > > > struct sh_dmae_chan *sh_chan = to_sh_chan(chan); > > > > struct sh_desc *desc, *_desc; > > > > LIST_HEAD(list); > > > > - int descs = sh_chan->descs_allocated; > > > > > > > > /* Protect against ISR */ > > > > spin_lock_irq(&sh_chan->desc_lock); > > > > @@ -440,9 +470,6 @@ static void sh_dmae_free_chan_resources(struct dma_chan *chan) > > > > > > > > spin_unlock_irq(&sh_chan->desc_lock); > > > > > > > > - if (descs > 0) > > > > - pm_runtime_put(sh_chan->dev); > > > > - > > > > list_for_each_entry_safe(desc, _desc, &list, node) > > > > kfree(desc); > > > > } > > > > @@ -676,7 +703,6 @@ static int sh_dmae_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd, > > > > struct sh_desc, node); > > > > desc->partial = (desc->hw.tcr - sh_dmae_readl(sh_chan, TCR)) << > > > > sh_chan->xmit_shift; > > > > - > > > > } > > > > spin_unlock_irqrestore(&sh_chan->desc_lock, flags); > > > > > > > > @@ -761,7 +787,13 @@ static dma_async_tx_callback __ld_cleanup(struct sh_dmae_chan *sh_chan, bool all > > > > async_tx_test_ack(&desc->async_tx)) || all) { > > > > /* Remove from ld_queue list */ > > > > desc->mark = DESC_IDLE; > > > > + > > > > list_move(&desc->node, &sh_chan->ld_free); > > > > + > > > > + if (list_empty(&sh_chan->ld_queue)) { > > > > + dev_dbg(sh_chan->dev, "Bring down channel %d\n", sh_chan->id); > > > > + pm_runtime_put(sh_chan->dev); > > > > + } > > > > } > > > > } > > > > > > > > @@ -791,16 +823,14 @@ static void sh_dmae_chan_ld_cleanup(struct sh_dmae_chan *sh_chan, bool all) > > > > ; > > > > } > > > > > > > > +/* Called under spin_lock_irq(&sh_chan->desc_lock) */ > > > > static void sh_chan_xfer_ld_queue(struct sh_dmae_chan *sh_chan) > > > > { > > > > struct sh_desc *desc; > > > > > > > > - spin_lock_irq(&sh_chan->desc_lock); > > > > /* DMA work check */ > > > > - if (dmae_is_busy(sh_chan)) { > > > > - spin_unlock_irq(&sh_chan->desc_lock); > > > > + if (dmae_is_busy(sh_chan)) > > > > return; > > > > - } > > > > > > > > /* Find the first not transferred descriptor */ > > > > list_for_each_entry(desc, &sh_chan->ld_queue, node) > > > > @@ -813,14 +843,18 @@ static void sh_chan_xfer_ld_queue(struct sh_dmae_chan *sh_chan) > > > > dmae_start(sh_chan); > > > > break; > > > > } > > > > - > > > > - spin_unlock_irq(&sh_chan->desc_lock); > > > > } > > > > > > > > static void sh_dmae_memcpy_issue_pending(struct dma_chan *chan) > > > > { > > > > struct sh_dmae_chan *sh_chan = to_sh_chan(chan); > > > > - sh_chan_xfer_ld_queue(sh_chan); > > > > + > > > > + spin_lock_irq(&sh_chan->desc_lock); > > > > + if (sh_chan->pm_state == DMAE_PM_ESTABLISHED) > > > > + sh_chan_xfer_ld_queue(sh_chan); > > > > + else > > > > + sh_chan->pm_state = DMAE_PM_PENDING; > > > > + spin_unlock_irq(&sh_chan->desc_lock); > > > > } > > > > > > > > static enum dma_status sh_dmae_tx_status(struct dma_chan *chan, > > > > @@ -913,6 +947,12 @@ static bool sh_dmae_reset(struct sh_dmae_device *shdev) > > > > > > > > list_splice_init(&sh_chan->ld_queue, &dl); > > > > > > > > + if (!list_empty(&dl)) { > > > > + dev_dbg(sh_chan->dev, "Bring down channel %d\n", sh_chan->id); > > > > + pm_runtime_put(sh_chan->dev); > > > > + } > > > > + sh_chan->pm_state = DMAE_PM_ESTABLISHED; > > > > + > > > > spin_unlock(&sh_chan->desc_lock); > > > > > > > > /* Complete all */ > > > > @@ -966,10 +1006,10 @@ static void dmae_do_tasklet(unsigned long data) > > > > break; > > > > } > > > > } > > > > - spin_unlock_irq(&sh_chan->desc_lock); > > > > - > > > > /* Next desc */ > > > > sh_chan_xfer_ld_queue(sh_chan); > > > > + spin_unlock_irq(&sh_chan->desc_lock); > > > > + > > > > sh_dmae_chan_ld_cleanup(sh_chan, false); > > > > } > > > > > > > > @@ -1037,7 +1077,9 @@ static int __devinit sh_dmae_chan_probe(struct sh_dmae_device *shdev, int id, > > > > return -ENOMEM; > > > > } > > > > > > > > - /* copy struct dma_device */ > > > > + new_sh_chan->pm_state = DMAE_PM_ESTABLISHED; > > > > + > > > > + /* reference struct dma_device */ > > > > new_sh_chan->common.device = &shdev->common; > > > > > > > > new_sh_chan->dev = shdev->common.dev; > > > > diff --git a/drivers/dma/shdma.h b/drivers/dma/shdma.h > > > > index dc56576..2b55a27 100644 > > > > --- a/drivers/dma/shdma.h > > > > +++ b/drivers/dma/shdma.h > > > > @@ -23,6 +23,12 @@ > > > > > > > > struct device; > > > > > > > > +enum dmae_pm_state { > > > > + DMAE_PM_ESTABLISHED, > > > > + DMAE_PM_BUSY, > > > > + DMAE_PM_PENDING, > > > > +}; > > > > + > > > > struct sh_dmae_chan { > > > > dma_cookie_t completed_cookie; /* The maximum cookie completed */ > > > > spinlock_t desc_lock; /* Descriptor operation lock */ > > > > @@ -38,6 +44,7 @@ struct sh_dmae_chan { > > > > u32 __iomem *base; > > > > char dev_id[16]; /* unique name per DMAC of channel */ > > > > int pm_error; > > > > + enum dmae_pm_state pm_state; > > > > }; > > > > > > > > struct sh_dmae_device { > > > > > > > > > > > > > > > > --- > > Guennadi Liakhovetski, Ph.D. > > Freelance Open-Source Software Developer > > http://www.open-technology.de/ > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ >
--- Guennadi Liakhovetski, Ph.D. Freelance Open-Source Software Developer http://www.open-technology.de/
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