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Date: Sat, 14 Nov 2015 15:27:49 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Jon Hunter <jonathanh@...dia.com>
Cc: Laxman Dewangan <ldewangan@...dia.com>,
Vinod Koul <vinod.koul@...el.com>,
Stephen Warren <swarren@...dotorg.org>,
Thierry Reding <thierry.reding@...il.com>,
Alexandre Courbot <gnurou@...il.com>,
dmaengine <dmaengine@...r.kernel.org>,
"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 1/6] dmaengine: tegra-apb: Correct runtime-pm usage
On Fri, Nov 13, 2015 at 6:39 PM, Jon Hunter <jonathanh@...dia.com> wrote:
> The tegra-apb DMA driver enables runtime-pm but never calls
> pm_runtime_get/put and hence the runtime-pm callbacks are never invoked.
> The driver manages the clocks by directly calling clk_prepare_enable()
> and clk_unprepare_disable().
>
> Fix this by replacing the clk_prepare_enable() and clk_disable_unprepare()
> with pm_runtime_get_sync() and pm_runtime_put(), respectively. Note that
> the consequence of this is that if runtime-pm is disabled, then the clocks
> will remain on the entire time the driver is loaded. However, if
> runtime-pm is disabled, then power is not most likely not a concern.
>
Have you tested these changes somehow?
See my comments below.
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> ---
> V3 changes:
> - Removed unnecessary update to local variables in suspend/resume
> V2 changes:
> - Fixed return value for allocating channel
> - Fixed test for return value from pm_runtime_get_sync()
>
> drivers/dma/tegra20-apb-dma.c | 43 ++++++++++++++++++-------------------------
> 1 file changed, 18 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> index c8f79dcaaee8..f68bccf55a24 100644
> --- a/drivers/dma/tegra20-apb-dma.c
> +++ b/drivers/dma/tegra20-apb-dma.c
> @@ -1186,10 +1186,12 @@ static int tegra_dma_alloc_chan_resources(struct dma_chan *dc)
>
> dma_cookie_init(&tdc->dma_chan);
> tdc->config_init = false;
> - ret = clk_prepare_enable(tdma->dma_clk);
> +
> + ret = pm_runtime_get_sync(tdma->dev);
> if (ret < 0)
> - dev_err(tdc2dev(tdc), "clk_prepare_enable failed: %d\n", ret);
> - return ret;
> + return ret;
> +
> + return 0;
This is a non-reachable code.
> }
>
> static void tegra_dma_free_chan_resources(struct dma_chan *dc)
> @@ -1232,7 +1234,7 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
> list_del(&sg_req->node);
> kfree(sg_req);
> }
> - clk_disable_unprepare(tdma->dma_clk);
> + pm_runtime_put(tdma->dev);
>
> tdc->slave_id = 0;
> }
> @@ -1356,20 +1358,14 @@ static int tegra_dma_probe(struct platform_device *pdev)
> spin_lock_init(&tdma->global_lock);
>
> pm_runtime_enable(&pdev->dev);
> - if (!pm_runtime_enabled(&pdev->dev)) {
> + if (!pm_runtime_enabled(&pdev->dev))
> ret = tegra_dma_runtime_resume(&pdev->dev);
I didn't check, but does this bring device to powered on state?
> - if (ret) {
> - dev_err(&pdev->dev, "dma_runtime_resume failed %d\n",
> - ret);
> - goto err_pm_disable;
> - }
> - }
> + else
> + ret = pm_runtime_get_sync(&pdev->dev);
>
> - /* Enable clock before accessing registers */
> - ret = clk_prepare_enable(tdma->dma_clk);
> if (ret < 0) {
> - dev_err(&pdev->dev, "clk_prepare_enable failed: %d\n", ret);
> - goto err_pm_disable;
> + pm_runtime_disable(&pdev->dev);
> + return ret;
> }
>
> /* Reset DMA controller */
> @@ -1382,7 +1378,7 @@ static int tegra_dma_probe(struct platform_device *pdev)
> tdma_write(tdma, TEGRA_APBDMA_CONTROL, 0);
> tdma_write(tdma, TEGRA_APBDMA_IRQ_MASK_SET, 0xFFFFFFFFul);
>
> - clk_disable_unprepare(tdma->dma_clk);
> + pm_runtime_put(&pdev->dev);
>
> INIT_LIST_HEAD(&tdma->dma_dev.channels);
> for (i = 0; i < cdata->nr_channels; i++) {
> @@ -1485,7 +1481,6 @@ err_irq:
> tasklet_kill(&tdc->tasklet);
> }
>
> -err_pm_disable:
> pm_runtime_disable(&pdev->dev);
> if (!pm_runtime_status_suspended(&pdev->dev))
> tegra_dma_runtime_suspend(&pdev->dev);
> @@ -1543,7 +1538,7 @@ static int tegra_dma_pm_suspend(struct device *dev)
> int ret;
>
> /* Enable clock before accessing register */
> - ret = tegra_dma_runtime_resume(dev);
> + ret = pm_runtime_get_sync(dev);
> if (ret < 0)
> return ret;
>
> @@ -1560,7 +1555,7 @@ static int tegra_dma_pm_suspend(struct device *dev)
> }
>
> /* Disable clock */
> - tegra_dma_runtime_suspend(dev);
> + pm_runtime_put(dev);
> return 0;
> }
>
> @@ -1571,7 +1566,7 @@ static int tegra_dma_pm_resume(struct device *dev)
> int ret;
>
> /* Enable clock before accessing register */
> - ret = tegra_dma_runtime_resume(dev);
> + ret = pm_runtime_get_sync(dev);
> if (ret < 0)
> return ret;
>
> @@ -1592,16 +1587,14 @@ static int tegra_dma_pm_resume(struct device *dev)
> }
>
> /* Disable clock */
> - tegra_dma_runtime_suspend(dev);
> + pm_runtime_put(dev);
> return 0;
> }
> #endif
>
> static const struct dev_pm_ops tegra_dma_dev_pm_ops = {
> -#ifdef CONFIG_PM
> - .runtime_suspend = tegra_dma_runtime_suspend,
> - .runtime_resume = tegra_dma_runtime_resume,
> -#endif
> + SET_RUNTIME_PM_OPS(tegra_dma_runtime_suspend, tegra_dma_runtime_resume,
> + NULL)
> SET_SYSTEM_SLEEP_PM_OPS(tegra_dma_pm_suspend, tegra_dma_pm_resume)
> };
>
> --
> 2.1.4
>
--
With Best Regards,
Andy Shevchenko
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