linux-kernel - [PATCH 11/13] soundwire: intel_init: handle power rail dependencies for clock stop mode

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Message-Id: <20200721203723.18305-12-yung-chuan.liao@linux.intel.com>
Date:   Wed, 22 Jul 2020 04:37:21 +0800
From:   Bard Liao <yung-chuan.liao@...ux.intel.com>
To:     alsa-devel@...a-project.org, vkoul@...nel.org
Cc:     vinod.koul@...aro.org, linux-kernel@...r.kernel.org, tiwai@...e.de,
        broonie@...nel.org, gregkh@...uxfoundation.org, jank@...ence.com,
        srinivas.kandagatla@...aro.org, rander.wang@...ux.intel.com,
        ranjani.sridharan@...ux.intel.com, hui.wang@...onical.com,
        pierre-louis.bossart@...ux.intel.com, sanyog.r.kale@...el.com,
        slawomir.blauciak@...el.com, mengdong.lin@...el.com,
        bard.liao@...el.com
Subject: [PATCH 11/13] soundwire: intel_init: handle power rail dependencies for clock stop mode

From: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>

When none of the clock stop quirks is specified, the Master IP will
assume the context is preserved and will not reset the Bus and restart
enumeration. Due to power rail dependencies, the HDaudio controller
needs to remain powered and prevented from executing its pm_runtime
suspend routine.

This choice of course has a power impact, and this mode should only be
selected when latency requirements are critical or the parent device
can enter D0ix modes.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
---
 drivers/soundwire/intel_init.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/soundwire/intel_init.c b/drivers/soundwire/intel_init.c
index 96c9af15c308..c0fddf76a6dc 100644
--- a/drivers/soundwire/intel_init.c
+++ b/drivers/soundwire/intel_init.c
@@ -14,6 +14,7 @@
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/soundwire/sdw_intel.h>
+#include <linux/pm_runtime.h>
 #include "cadence_master.h"
 #include "intel.h"
 
@@ -72,6 +73,9 @@ static int sdw_intel_cleanup(struct sdw_intel_ctx *ctx)
 			pm_runtime_disable(&link->pdev->dev);
 			platform_device_unregister(link->pdev);
 		}
+
+		if (!link->clock_stop_quirks)
+			pm_runtime_put_noidle(link->dev);
 	}
 
 	return 0;
@@ -337,6 +341,16 @@ sdw_intel_startup_controller(struct sdw_intel_ctx *ctx)
 			continue;
 
 		intel_master_startup(link->pdev);
+
+		if (!link->clock_stop_quirks) {
+			/*
+			 * we need to prevent the parent PCI device
+			 * from entering pm_runtime suspend, so that
+			 * power rails to the SoundWire IP are not
+			 * turned off.
+			 */
+			pm_runtime_get_noresume(link->dev);
+		}
 	}
 
 	return 0;
-- 
2.17.1