[PATCH 3/3] regulator: qcom_spmi: don't take a sleeping lock in the SAW IPI

[Dmitry Baryshkov]

The SAW voltage change runs on CPU 0 from an IPI, but it reaches the SAW
registers through the syscon regmap, which is protected by a spinlock_t.
That is a sleeping lock on PREEMPT_RT, and lockdep complains as soon as
VDD_APCC actually changes voltage:

  BUG: Invalid wait context
  ...
  regmap_lock_spinlock+0x18/0x30
  regmap_read+0x3c/0x78
  spmi_saw_set_vdd+0x50/0x1ac
  __flush_smp_call_function_queue+0x1ac/0x334

Map the SAW with a regmap of our own that uses a raw spinlock, and fail
the probe when that cannot be done instead of carrying an error pointer
around as the SAW regmap.

Fixes: 0caecaa87202 ("regulator: qcom_spmi: Add support for SAW")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
---
 drivers/regulator/Kconfig               |  1 +
 drivers/regulator/qcom_spmi-regulator.c | 35 +++++++++++++++++++++++++--------
 2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index be6b72daa76f..83a76b78e58c 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -1210,6 +1210,7 @@ config REGULATOR_QCOM_SMD_RPM
 config REGULATOR_QCOM_SPMI
 	tristate "Qualcomm SPMI regulator driver"
 	depends on SPMI || COMPILE_TEST
+	select REGMAP_MMIO
 	help
 	  If you say yes to this option, support will be included for the
 	  regulators found in Qualcomm SPMI PMICs.
diff --git a/drivers/regulator/qcom_spmi-regulator.c b/drivers/regulator/qcom_spmi-regulator.c
index c1a41ce70b36..a04ddb1eac94 100644
--- a/drivers/regulator/qcom_spmi-regulator.c
+++ b/drivers/regulator/qcom_spmi-regulator.c
@@ -12,13 +12,13 @@
 #include <linux/bitops.h>
 #include <linux/slab.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/ktime.h>
 #include <linux/regulator/driver.h>
 #include <linux/regmap.h>
 #include <linux/list.h>
-#include <linux/mfd/syscon.h>
 #include <linux/io.h>
 
 /* Pin control enable input pins. */
@@ -1335,6 +1335,14 @@ static irqreturn_t spmi_regulator_vs_ocp_isr(int irq, void *data)
 
 static struct regmap *saw_regmap;
 
+static const struct regmap_config saw_regmap_config = {
+	.name = "saw",
+	.reg_bits = 32,
+	.val_bits = 32,
+	.reg_stride = 4,
+	.use_raw_spinlock = true,
+};
+
 static void spmi_saw_set_vdd(void *data)
 {
 	u32 vctl, data3, avs_ctl, pmic_sts;
@@ -2504,7 +2512,8 @@ static int qcom_spmi_regulator_probe(struct platform_device *pdev)
 	const char *name;
 	struct device *dev = &pdev->dev;
 	struct device_node *node = pdev->dev.of_node;
-	struct device_node *syscon, *reg_node;
+	struct device_node *saw, *reg_node;
+	void __iomem *saw_base;
 	struct property *reg_prop;
 	int ret, lenp;
 	struct list_head *vreg_list;
@@ -2523,12 +2532,22 @@ static int qcom_spmi_regulator_probe(struct platform_device *pdev)
 	if (!reg)
 		return -ENODEV;
 
-	syscon = of_parse_phandle(node, "qcom,saw-reg", 0);
-	if (syscon) {
-		saw_regmap = syscon_node_to_regmap(syscon);
-		of_node_put(syscon);
-		if (IS_ERR(saw_regmap))
-			dev_err(dev, "ERROR reading SAW regmap\n");
+	saw = of_parse_phandle(node, "qcom,saw-reg", 0);
+	if (saw) {
+		saw_base = devm_of_iomap(dev, saw, 0, NULL);
+		of_node_put(saw);
+		if (IS_ERR(saw_base))
+			return dev_err_probe(dev, PTR_ERR(saw_base),
+					     "failed to map the SAW\n");
+
+		saw_regmap = devm_regmap_init_mmio(dev, saw_base,
+						   &saw_regmap_config);
+		if (IS_ERR(saw_regmap)) {
+			ret = PTR_ERR(saw_regmap);
+			saw_regmap = NULL;
+			return dev_err_probe(dev, ret,
+					     "failed to set the SAW regmap up\n");
+		}
 	}
 
 	for (; reg->name; reg++) {

-- 
2.47.3