linux-kernel - [PATCH v2] spi: spi-sun6i: enable autosuspend feature

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Date:   Mon, 19 Oct 2020 18:03:43 +0300
From:   Alexander Kochetkov <al.kochet@...il.com>
To:     Mark Brown <broonie@...nel.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>
Cc:     linux-spi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Alexander Kochetkov <al.kochet@...il.com>
Subject: [PATCH v2] spi: spi-sun6i: enable autosuspend feature

From: Alexander Kochetkov <al.kochet@...il.com>

If SPI is used for periodic polling any sensor, significant delays
sometimes appear. Switching on module clocks during resume lead to delays.
Enabling autosuspend mode causes the controller to not suspend between
SPI transfers and the delays disappear.

The commit also remove unnecessary call to pm_runtime_idle() used
to explicit put device to suspended state. Without pm_runtime_idle() PM
core will put device in the suspended state just after probe() returns.

Signed-off-by: Alexander Kochetkov <al.kochet@...il.com>
---

Changes in v2:
- Extend commit description with explanation about removal
  of pm_runtime_idle()


 drivers/spi/spi-sun6i.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
index 29ea1e87ce7e..86f29c3e335a 100644
--- a/drivers/spi/spi-sun6i.c
+++ b/drivers/spi/spi-sun6i.c
@@ -22,6 +22,8 @@
 
 #include <linux/spi/spi.h>
 
+#define SUN6I_AUTOSUSPEND_TIMEOUT	2000
+
 #define SUN6I_FIFO_DEPTH		128
 #define SUN8I_FIFO_DEPTH		64
 
@@ -652,9 +654,10 @@ static int sun6i_spi_probe(struct platform_device *pdev)
 		goto err_free_dma_rx;
 	}
 
+	pm_runtime_set_autosuspend_delay(&pdev->dev, SUN6I_AUTOSUSPEND_TIMEOUT);
+	pm_runtime_use_autosuspend(&pdev->dev);
 	pm_runtime_set_active(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
-	pm_runtime_idle(&pdev->dev);
 
 	ret = devm_spi_register_master(&pdev->dev, master);
 	if (ret) {
-- 
2.17.1