linux-kernel - [PATCH 03/10] drivers: nvmem: Fix voltage settings for QTI qfprom-efuse

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Date:   Tue, 30 Mar 2021 12:12:34 +0100
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     gregkh@...uxfoundation.org
Cc:     linux-kernel@...r.kernel.org,
        Ravi Kumar Bokka <rbokka@...eaurora.org>,
        Douglas Anderson <dianders@...omium.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: [PATCH 03/10] drivers: nvmem: Fix voltage settings for QTI qfprom-efuse

From: Ravi Kumar Bokka <rbokka@...eaurora.org>

QFPROM controller hardware requires 1.8V min for fuse blowing.
So, this change sets the voltage to 1.8V, required to blow the fuse
for qfprom-efuse controller.

To disable fuse blowing, we set the voltage to 0V since this may
be a shared rail and may be able to run at a lower rate when we're
not blowing fuses.

Fixes: 93b4e49f8c86 ("nvmem: qfprom: Add fuse blowing support")
Reported-by: Douglas Anderson <dianders@...omium.org>
Suggested-by: Douglas Anderson <dianders@...omium.org>
Signed-off-by: Ravi Kumar Bokka <rbokka@...eaurora.org>
Reviewed-by: Douglas Anderson <dianders@...omium.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
---
 drivers/nvmem/qfprom.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
index 6cace24dfbf7..100d69d8f2e1 100644
--- a/drivers/nvmem/qfprom.c
+++ b/drivers/nvmem/qfprom.c
@@ -127,6 +127,16 @@ static void qfprom_disable_fuse_blowing(const struct qfprom_priv *priv,
 {
 	int ret;
 
+	/*
+	 * This may be a shared rail and may be able to run at a lower rate
+	 * when we're not blowing fuses.  At the moment, the regulator framework
+	 * applies voltage constraints even on disabled rails, so remove our
+	 * constraints and allow the rail to be adjusted by other users.
+	 */
+	ret = regulator_set_voltage(priv->vcc, 0, INT_MAX);
+	if (ret)
+		dev_warn(priv->dev, "Failed to set 0 voltage (ignoring)\n");
+
 	ret = regulator_disable(priv->vcc);
 	if (ret)
 		dev_warn(priv->dev, "Failed to disable regulator (ignoring)\n");
@@ -172,6 +182,17 @@ static int qfprom_enable_fuse_blowing(const struct qfprom_priv *priv,
 		goto err_clk_prepared;
 	}
 
+	/*
+	 * Hardware requires 1.8V min for fuse blowing; this may be
+	 * a rail shared do don't specify a max--regulator constraints
+	 * will handle.
+	 */
+	ret = regulator_set_voltage(priv->vcc, 1800000, INT_MAX);
+	if (ret) {
+		dev_err(priv->dev, "Failed to set 1.8 voltage\n");
+		goto err_clk_rate_set;
+	}
+
 	ret = regulator_enable(priv->vcc);
 	if (ret) {
 		dev_err(priv->dev, "Failed to enable regulator\n");
-- 
2.21.0