dmaengine Archive on lore.kernel.org
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From: Dmitry Osipenko <digetx@gmail.com>
To: "Laxman Dewangan" <ldewangan@nvidia.com>,
	"Vinod Koul" <vkoul@kernel.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Thierry Reding" <thierry.reding@gmail.com>,
	"Jonathan Hunter" <jonathanh@nvidia.com>,
	"Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: dmaengine@vger.kernel.org, linux-tegra@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH v7 14/19] dmaengine: tegra-apb: Keep clock enabled only during of DMA transfer
Date: Mon,  3 Feb 2020 01:28:49 +0300
Message-ID: <20200202222854.18409-15-digetx@gmail.com> (raw)
In-Reply-To: <20200202222854.18409-1-digetx@gmail.com>

It's a bit impractical to enable hardware's clock at the time of DMA
channel's allocation because most of DMA client drivers allocate DMA
channel at the time of the driver's probing, and thus, DMA clock is kept
always-enabled in practice, defeating the whole purpose of runtime PM.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/dma/tegra20-apb-dma.c | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index 50abce608318..92535b962e64 100644
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -605,9 +605,14 @@ static void handle_once_dma_done(struct tegra_dma_channel *tdc,
 	list_add_tail(&sgreq->node, &tdc->free_sg_req);
 
 	/* Do not start DMA if it is going to be terminate */
-	if (to_terminate || list_empty(&tdc->pending_sg_req))
+	if (to_terminate)
 		return;
 
+	if (list_empty(&tdc->pending_sg_req)) {
+		pm_runtime_put(tdc->tdma->dev);
+		return;
+	}
+
 	tdc_start_head_req(tdc);
 }
 
@@ -713,6 +718,7 @@ static void tegra_dma_issue_pending(struct dma_chan *dc)
 {
 	struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
 	unsigned long flags;
+	int err;
 
 	spin_lock_irqsave(&tdc->lock, flags);
 	if (list_empty(&tdc->pending_sg_req)) {
@@ -720,6 +726,12 @@ static void tegra_dma_issue_pending(struct dma_chan *dc)
 		goto end;
 	}
 	if (!tdc->busy) {
+		err = pm_runtime_get_sync(tdc->tdma->dev);
+		if (err < 0) {
+			dev_err(tdc2dev(tdc), "Failed to enable DMA\n");
+			goto end;
+		}
+
 		tdc_start_head_req(tdc);
 
 		/* Continuous single mode: Configure next req */
@@ -778,6 +790,8 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
 	}
 	tegra_dma_resume(tdc);
 
+	pm_runtime_put(tdc->tdma->dev);
+
 skip_dma_stop:
 	tegra_dma_abort_all(tdc);
 
@@ -1272,22 +1286,15 @@ tegra_dma_prep_dma_cyclic(struct dma_chan *dc, dma_addr_t buf_addr,
 static int tegra_dma_alloc_chan_resources(struct dma_chan *dc)
 {
 	struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
-	struct tegra_dma *tdma = tdc->tdma;
-	int ret;
 
 	dma_cookie_init(&tdc->dma_chan);
 
-	ret = pm_runtime_get_sync(tdma->dev);
-	if (ret < 0)
-		return ret;
-
 	return 0;
 }
 
 static void tegra_dma_free_chan_resources(struct dma_chan *dc)
 {
 	struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
-	struct tegra_dma *tdma = tdc->tdma;
 	struct tegra_dma_desc *dma_desc;
 	struct tegra_dma_sg_req *sg_req;
 	struct list_head dma_desc_list;
@@ -1320,7 +1327,6 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
 		list_del(&sg_req->node);
 		kfree(sg_req);
 	}
-	pm_runtime_put(tdma->dev);
 
 	tdc->slave_id = TEGRA_APBDMA_SLAVE_ID_INVALID;
 }
@@ -1420,6 +1426,11 @@ static int tegra_dma_probe(struct platform_device *pdev)
 
 	spin_lock_init(&tdma->global_lock);
 
+	ret = clk_prepare(tdma->dma_clk);
+	if (ret)
+		return ret;
+
+	pm_runtime_irq_safe(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
 
 	ret = pm_runtime_get_sync(&pdev->dev);
@@ -1535,6 +1546,7 @@ static int tegra_dma_probe(struct platform_device *pdev)
 
 err_pm_disable:
 	pm_runtime_disable(&pdev->dev);
+	clk_unprepare(tdma->dma_clk);
 
 	return ret;
 }
@@ -1545,6 +1557,7 @@ static int tegra_dma_remove(struct platform_device *pdev)
 
 	dma_async_device_unregister(&tdma->dma_dev);
 	pm_runtime_disable(&pdev->dev);
+	clk_unprepare(tdma->dma_clk);
 
 	return 0;
 }
@@ -1573,7 +1586,7 @@ static int tegra_dma_runtime_suspend(struct device *dev)
 						  TEGRA_APBDMA_CHAN_WCOUNT);
 	}
 
-	clk_disable_unprepare(tdma->dma_clk);
+	clk_disable(tdma->dma_clk);
 
 	return 0;
 }
@@ -1584,7 +1597,7 @@ static int tegra_dma_runtime_resume(struct device *dev)
 	unsigned int i;
 	int ret;
 
-	ret = clk_prepare_enable(tdma->dma_clk);
+	ret = clk_enable(tdma->dma_clk);
 	if (ret < 0) {
 		dev_err(dev, "clk_enable failed: %d\n", ret);
 		return ret;
-- 
2.24.0


  parent reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-02 22:28 [PATCH v7 00/19] NVIDIA Tegra APB DMA driver fixes and improvements Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 01/19] dmaengine: tegra-apb: Fix use-after-free Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 02/19] dmaengine: tegra-apb: Prevent race conditions of tasklet vs free list Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 03/19] dmaengine: tegra-apb: Implement synchronization hook Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 04/19] dmaengine: tegra-apb: Prevent race conditions on channel's freeing Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 05/19] dmaengine: tegra-apb: Clean up tasklet releasing Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 06/19] dmaengine: tegra-apb: Use devm_platform_ioremap_resource Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 07/19] dmaengine: tegra-apb: Use devm_request_irq Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 08/19] dmaengine: tegra-apb: Fix coding style problems Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 09/19] dmaengine: tegra-apb: Remove unneeded initialization of tdc->config_init Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 10/19] dmaengine: tegra-apb: Remove assumptions about unavailable runtime PM Dmitry Osipenko
2020-02-04 14:51   ` Jon Hunter
2020-02-02 22:28 ` [PATCH v7 11/19] dmaengine: tegra-apb: Remove pending_sg_req checking from tdc_start_head_req Dmitry Osipenko
2020-02-04 14:53   ` Jon Hunter
2020-02-02 22:28 ` [PATCH v7 12/19] dmaengine: tegra-apb: Remove handling of unrealistic error condition Dmitry Osipenko
2020-02-04 11:52   ` Jon Hunter
2020-02-04 22:17     ` Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 13/19] dmaengine: tegra-apb: Don't stop cyclic DMA in a case of " Dmitry Osipenko
2020-02-04 12:02   ` Jon Hunter
2020-02-04 15:55     ` Dmitry Osipenko
2020-02-02 22:28 ` Dmitry Osipenko [this message]
2020-02-06 13:50   ` [PATCH v7 14/19] dmaengine: tegra-apb: Keep clock enabled only during of DMA transfer Jon Hunter
2020-02-06 14:31     ` Dmitry Osipenko
2020-02-06 14:33       ` Jon Hunter
2020-02-02 22:28 ` [PATCH v7 15/19] dmaengine: tegra-apb: Clean up suspend-resume Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 16/19] dmaengine: tegra-apb: Add missing of_dma_controller_free Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 17/19] dmaengine: tegra-apb: Allow to compile as a loadable kernel module Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 18/19] dmaengine: tegra-apb: Remove MODULE_ALIAS Dmitry Osipenko
2020-02-02 22:28 ` [PATCH v7 19/19] dmaengine: tegra-apb: Support COMPILE_TEST Dmitry Osipenko

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