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Message-id: <1415197299.30831.10.camel@AMDC1943>
Date: Wed, 05 Nov 2014 15:21:39 +0100
From: Krzysztof Kozlowski <k.kozlowski@...sung.com>
To: Vinod Koul <vinod.koul@...el.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
Jonathan Corbet <corbet@....net>,
Russell King <linux@....linux.org.uk>,
Dan Williams <dan.j.williams@...el.com>,
Ulf Hansson <ulf.hansson@...aro.org>,
Alan Stern <stern@...land.harvard.edu>,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
dmaengine@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
Michal Simek <michal.simek@...inx.com>,
Kevin Hilman <khilman@...nel.org>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Kyungmin Park <kyungmin.park@...sung.com>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v9 3/4] dma: pl330: add Power Management support
On śro, 2014-11-05 at 19:31 +0530, Vinod Koul wrote:
> On Tue, Nov 04, 2014 at 01:52:49PM +0100, Krzysztof Kozlowski wrote:
> > 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);
> Why do we need _get() here? If we are terminating then channel is already in
> use so should be active?
The runtime PM is kind a aggressive here so I think the device could be
suspended in that moment. The terminate may happen some time after
channel was used.
>
> > 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);
> Well else should be error here, so I would expect loud complains in that
> case here
The 'else' path is fine. Just the terminate command was triggered when
work_list was empty.
The 'else' here could be triggered easily with:
echo dma0chan0 > /sys/module/dmatest/parameters/channel
echo 1 > /sys/module/dmatest/parameters/run
sleep 3
cat /sys/module/dmatest/parameters/run
> > +
> > 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);
> Again why do we need _get() in free callback.
Hmmm... I think because of the same reason as terminate_all. It may
happen after some time since last usage. The driver here stops thread
which requires device resumed.
>
> > 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 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);
> IIUC this sets .suspend and .resume, aren't you trying to add runtime
> support as well?
> Did you want UNIVERSAL_DEV_PM_OPS() ?
The runtime suspend and resume callbacks are provided by amba/bus.c.
>
> > +
> > 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
> >
>
> Last please use the right subsystem name, dmaengine is patches.
Sure, I just got confused by name of directory.
Thanks for looking at code,
Krzysztof
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