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Date: Wed, 15 Oct 2014 09:19:59 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc: Russell King <linux@....linux.org.uk>,
Dan Williams <dan.j.williams@...el.com>,
Vinod Koul <vinod.koul@...el.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
dmaengine@...r.kernel.org, Grant Likely <grant.likely@...aro.org>,
Lars-Peter Clausen <lars@...afoo.de>,
Michal Simek <michal.simek@...inx.com>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
Randy Dunlap <rdunlap@...radead.org>,
Alan Stern <stern@...land.harvard.edu>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
Kyungmin Park <kyungmin.park@...sung.com>,
Marek Szyprowski <m.szyprowski@...sung.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v7 4/5] dma: pl330: add Power Management support
On 24 September 2014 15:50, Krzysztof Kozlowski <k.kozlowski@...sung.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@...sung.com>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
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
>
--
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