linux-kernel - [PATCH v1 08/30] soc/tegra: regulators: Support Tegra SoC device sync state API

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Message-Id: <20201104234427.26477-9-digetx@gmail.com>
Date:   Thu,  5 Nov 2020 02:44:05 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Peter Chen <Peter.Chen@....com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lee Jones <lee.jones@...aro.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>
Cc:     linux-samsung-soc@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-usb@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-media@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: [PATCH v1 08/30] soc/tegra: regulators: Support Tegra SoC device sync state API

Downscale of the CORE voltage isn't allowed because some hardware units,
which are supplied by the CORE regulator, usually left ON at a boot time.
The new sync state API resolves this problem for us. All drivers of the
devices that are known to be ON at a boot time now should sync theirs
state. Once everything is synced, the voltage of the CORE domain could
be scaled without any limitations.

Make Tegra20/30 regulator couplers to use the new sync state API.

Tested-by: Peter Geis <pgwipeout@...il.com>
Tested-by: Nicolas Chauvet <kwizart@...il.com>
Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/soc/tegra/regulators-tegra20.c | 19 ++++++++++++++++++-
 drivers/soc/tegra/regulators-tegra30.c | 22 +++++++++++++++++++++-
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/tegra/regulators-tegra20.c b/drivers/soc/tegra/regulators-tegra20.c
index 367a71a3cd10..8782e399a58c 100644
--- a/drivers/soc/tegra/regulators-tegra20.c
+++ b/drivers/soc/tegra/regulators-tegra20.c
@@ -16,6 +16,8 @@
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>
 
+#include <soc/tegra/common.h>
+
 struct tegra_regulator_coupler {
 	struct regulator_coupler coupler;
 	struct regulator_dev *core_rdev;
@@ -38,6 +40,21 @@ static int tegra20_core_limit(struct tegra_regulator_coupler *tegra,
 	int core_cur_uV;
 	int err;
 
+	/*
+	 * Tegra20 SoC has critical DVFS-capable devices that are
+	 * permanently-active or active at a boot time, like EMC
+	 * (DRAM controller) or Host1x bus for example.
+	 *
+	 * The voltage of a CORE SoC power domain shall not be dropped below
+	 * a minimum level, which is determined by device's clock rate.
+	 * This means that we can't fully allow CORE voltage scaling until
+	 * the state of all DVFS-critical CORE devices is synced.
+	 */
+	if (tegra_soc_dvfs_state_synced()) {
+		pr_info_once("voltage state synced\n");
+		return 0;
+	}
+
 	if (tegra->core_min_uV > 0)
 		return tegra->core_min_uV;
 
@@ -58,7 +75,7 @@ static int tegra20_core_limit(struct tegra_regulator_coupler *tegra,
 	 */
 	tegra->core_min_uV = core_max_uV;
 
-	pr_info("core minimum voltage limited to %duV\n", tegra->core_min_uV);
+	pr_info("core voltage initialized to %duV\n", tegra->core_min_uV);
 
 	return tegra->core_min_uV;
 }
diff --git a/drivers/soc/tegra/regulators-tegra30.c b/drivers/soc/tegra/regulators-tegra30.c
index 7f21f31de09d..f7a5260edffe 100644
--- a/drivers/soc/tegra/regulators-tegra30.c
+++ b/drivers/soc/tegra/regulators-tegra30.c
@@ -16,6 +16,7 @@
 #include <linux/regulator/driver.h>
 #include <linux/regulator/machine.h>
 
+#include <soc/tegra/common.h>
 #include <soc/tegra/fuse.h>
 
 struct tegra_regulator_coupler {
@@ -39,6 +40,21 @@ static int tegra30_core_limit(struct tegra_regulator_coupler *tegra,
 	int core_cur_uV;
 	int err;
 
+	/*
+	 * Tegra30 SoC has critical DVFS-capable devices that are
+	 * permanently-active or active at a boot time, like EMC
+	 * (DRAM controller) or Host1x bus for example.
+	 *
+	 * The voltage of a CORE SoC power domain shall not be dropped below
+	 * a minimum level, which is determined by device's clock rate.
+	 * This means that we can't fully allow CORE voltage scaling until
+	 * the state of all DVFS-critical CORE devices is synced.
+	 */
+	if (tegra_soc_dvfs_state_synced()) {
+		pr_info_once("voltage state synced\n");
+		return 0;
+	}
+
 	if (tegra->core_min_uV > 0)
 		return tegra->core_min_uV;
 
@@ -59,7 +75,7 @@ static int tegra30_core_limit(struct tegra_regulator_coupler *tegra,
 	 */
 	tegra->core_min_uV = core_max_uV;
 
-	pr_info("core minimum voltage limited to %duV\n", tegra->core_min_uV);
+	pr_info("core voltage initialized to %duV\n", tegra->core_min_uV);
 
 	return tegra->core_min_uV;
 }
@@ -143,6 +159,10 @@ static int tegra30_voltage_update(struct tegra_regulator_coupler *tegra,
 	if (core_min_uV < 0)
 		return core_min_uV;
 
+	err = regulator_check_voltage(core_rdev, &core_min_uV, &core_max_uV);
+	if (err)
+		return err;
+
 	err = regulator_check_consumers(core_rdev, &core_min_uV, &core_max_uV,
 					PM_SUSPEND_ON);
 	if (err)
-- 
2.27.0