linux-kernel - [PATCH 3/3] nvmem: qfprom: Don't touch certain fuses

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Date:   Tue, 29 Sep 2020 13:58:07 -0700
From:   Evan Green <evgreen@...omium.org>
To:     Rob Herring <robh+dt@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Douglas Anderson <dianders@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Evan Green <evgreen@...omium.org>, linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] nvmem: qfprom: Don't touch certain fuses

Some fuse ranges are protected by the XPU such that the AP cannot
access them. Attempting to do so causes an SError. Use the newly
introduced per-soc compatible string to attach the set of regions
we should not access. Then tiptoe around those regions.

Signed-off-by: Evan Green <evgreen@...omium.org>
---

 drivers/nvmem/qfprom.c | 55 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 51 insertions(+), 4 deletions(-)

diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
index 5e9e60e2e591d..feea39ae52164 100644
--- a/drivers/nvmem/qfprom.c
+++ b/drivers/nvmem/qfprom.c
@@ -12,6 +12,7 @@
 #include <linux/mod_devicetable.h>
 #include <linux/nvmem-provider.h>
 #include <linux/platform_device.h>
+#include <linux/property.h>
 #include <linux/regulator/consumer.h>
 
 /* Blow timer clock frequency in Mhz */
@@ -51,6 +52,17 @@ struct qfprom_soc_data {
 	u32 qfprom_blow_set_freq;
 };
 
+/**
+ * struct qfprom_keepout_region - registers to avoid touching.
+ *
+ * @start: The first byte offset to avoid.
+ * @end: One after the last byte offset to avoid.
+ */
+struct qfprom_keepout_region {
+	u32 start;
+	u32 end;
+};
+
 /**
  * struct qfprom_priv - structure holding qfprom attributes
  *
@@ -63,6 +75,7 @@ struct qfprom_soc_data {
  * @secclk:       Clock supply.
  * @vcc:          Regulator supply.
  * @soc_data:     Data that for things that varies from SoC to SoC.
+ * @keepout:      Fuse regions not to access, as they may cause SErrors.
  */
 struct qfprom_priv {
 	void __iomem *qfpraw;
@@ -73,6 +86,7 @@ struct qfprom_priv {
 	struct clk *secclk;
 	struct regulator *vcc;
 	const struct qfprom_soc_data *soc_data;
+	const struct qfprom_keepout_region *keepout;
 };
 
 /**
@@ -88,6 +102,12 @@ struct qfprom_touched_values {
 	u32 timer_val;
 };
 
+const struct qfprom_keepout_region sc7180_qfprom[] = {
+	{.start = 0x128, .end = 0x148},
+	{.start = 0x220, .end = 0x228},
+	{} /* Sentinal where start == end. */
+};
+
 /**
  * qfprom_disable_fuse_blowing() - Undo enabling of fuse blowing.
  * @priv: Our driver data.
@@ -171,6 +191,23 @@ static int qfprom_enable_fuse_blowing(const struct qfprom_priv *priv,
 	return ret;
 }
 
+static int qfprom_check_reg(struct qfprom_priv *priv, unsigned int reg)
+{
+	const struct qfprom_keepout_region *keepout = priv->keepout;
+
+	if (!keepout)
+		return 1;
+
+	while (keepout->start != keepout->end) {
+		if ((reg >= keepout->start) && (reg < keepout->end))
+			return 0;
+
+		keepout++;
+	}
+
+	return 1;
+}
+
 /**
  * qfprom_efuse_reg_write() - Write to fuses.
  * @context: Our driver data.
@@ -228,8 +265,10 @@ static int qfprom_reg_write(void *context, unsigned int reg, void *_val,
 		goto exit_enabled_fuse_blowing;
 	}
 
-	for (i = 0; i < words; i++)
-		writel(value[i], priv->qfpraw + reg + (i * 4));
+	for (i = 0; i < words; i++) {
+		if (qfprom_check_reg(priv, reg + (i * 4)))
+			writel(value[i], priv->qfpraw + reg + (i * 4));
+	}
 
 	ret = readl_relaxed_poll_timeout(
 		priv->qfpconf + QFPROM_BLOW_STATUS_OFFSET,
@@ -257,8 +296,14 @@ static int qfprom_reg_read(void *context,
 	if (read_raw_data && priv->qfpraw)
 		base = priv->qfpraw;
 
-	while (words--)
-		*val++ = readb(base + reg + i++);
+	while (words--) {
+		if (qfprom_check_reg(priv, reg + i))
+			*val++ = readb(base + reg + i);
+		else
+			*val++ = 0;
+
+		i++;
+	}
 
 	return 0;
 }
@@ -299,6 +344,7 @@ static int qfprom_probe(struct platform_device *pdev)
 	econfig.priv = priv;
 
 	priv->dev = dev;
+	priv->keepout = device_get_match_data(dev);
 
 	/*
 	 * If more than one region is provided then the OS has the ability
@@ -354,6 +400,7 @@ static int qfprom_probe(struct platform_device *pdev)
 
 static const struct of_device_id qfprom_of_match[] = {
 	{ .compatible = "qcom,qfprom",},
+	{ .compatible = "qcom,sc7180-qfprom", .data = &sc7180_qfprom},
 	{/* sentinel */},
 };
 MODULE_DEVICE_TABLE(of, qfprom_of_match);
-- 
2.26.2