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Date: Thu, 25 Aug 2011 16:55:03 +0200 (CEST)
From: Guennadi Liakhovetski <g.liakhovetski@....de>
To: "Koul, Vinod" <vinod.koul@...el.com>
cc: linux-kernel@...r.kernel.org, linux-sh@...r.kernel.org,
Dan Williams <dan.j.williams@...el.com>,
Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH] dma: shdma: transfer based runtime PM
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@....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@...r.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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