[PATCH 3/4] nvmem: ocotp: handle too early calls into ocotp driver gracefully

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

HAB code calls into OCOTP driver by relying on a global imx_ocotp
variable that's populated on driver probe.

For board code that calls a HAB function to early, this may end up
dereferencing a NULL pointer, so let's return -EPROBE_DEFER in that
case or if deep probe is enabled, just probe the OCOTP directly.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 drivers/clk/imx/clk-vf610.c |  5 ++++-
 drivers/nvmem/ocotp.c       | 41 +++++++++++++++++++++++++++++++++++--
 include/mach/imx/ocotp.h    |  2 +-
 3 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/imx/clk-vf610.c b/drivers/clk/imx/clk-vf610.c
index 89899e0dc9b4..112f64df9b74 100644
--- a/drivers/clk/imx/clk-vf610.c
+++ b/drivers/clk/imx/clk-vf610.c
@@ -568,13 +568,16 @@ static int vf610_switch_cpu_clock_to_400mhz(void)
 static int vf610_switch_cpu_clock(void)
 {
 	int ret;
-	bool sense_enable;
+	int sense_enable;
 	uint32_t speed_grading;
 
 	if (!of_machine_is_compatible("fsl,vf610"))
 		return 0;
 
 	sense_enable = imx_ocotp_sense_enable(true);
+	if (sense_enable < 0)
+		return sense_enable;
+
 	ret = imx_ocotp_read_field(VF610_OCOTP_SPEED_GRADING, &speed_grading);
 	imx_ocotp_sense_enable(sense_enable);
 	if (ret < 0)
diff --git a/drivers/nvmem/ocotp.c b/drivers/nvmem/ocotp.c
index 8ba7a8af5da5..c22e5d9585fa 100644
--- a/drivers/nvmem/ocotp.c
+++ b/drivers/nvmem/ocotp.c
@@ -14,6 +14,7 @@
  */
 
 #include <common.h>
+#include <deep-probe.h>
 #include <driver.h>
 #include <malloc.h>
 #include <xfuncs.h>
@@ -497,11 +498,17 @@ static void imx_ocotp_field_decode(uint32_t field, unsigned *word,
 	*mask = GENMASK(width, 0);
 }
 
+static int imx_ocotp_ensure_probed(void);
+
 int imx_ocotp_read_field(uint32_t field, unsigned *value)
 {
 	unsigned word, bit, mask, val;
 	int ret;
 
+	ret = imx_ocotp_ensure_probed();
+	if (ret)
+		return ret;
+
 	imx_ocotp_field_decode(field, &word, &bit, &mask);
 
 	ret = imx_ocotp_reg_read(imx_ocotp, word, &val);
@@ -524,6 +531,10 @@ int imx_ocotp_write_field(uint32_t field, unsigned value)
 	unsigned word, bit, mask;
 	int ret;
 
+	ret = imx_ocotp_ensure_probed();
+	if (ret)
+		return ret;
+
 	imx_ocotp_field_decode(field, &word, &bit, &mask);
 
 	value &= mask;
@@ -541,14 +552,27 @@ int imx_ocotp_write_field(uint32_t field, unsigned value)
 
 int imx_ocotp_permanent_write(int enable)
 {
+	int ret;
+
+	ret = imx_ocotp_ensure_probed();
+	if (ret)
+		return ret;
+
 	imx_ocotp->permanent_write_enable = enable;
 
 	return 0;
 }
 
-bool imx_ocotp_sense_enable(bool enable)
+int imx_ocotp_sense_enable(bool enable)
 {
-	const bool old_value = imx_ocotp->sense_enable;
+	bool old_value;
+	int ret;
+
+	ret = imx_ocotp_ensure_probed();
+	if (ret)
+		return ret;
+
+	old_value = imx_ocotp->sense_enable;
 	imx_ocotp->sense_enable = enable;
 	return old_value;
 }
@@ -994,6 +1018,19 @@ static __maybe_unused struct of_device_id imx_ocotp_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, imx_ocotp_dt_ids);
 
+static int imx_ocotp_ensure_probed(void)
+{
+	if (!imx_ocotp && deep_probe_is_supported()) {
+		int ret;
+
+		ret = of_devices_ensure_probed_by_dev_id(imx_ocotp_dt_ids);
+		if (ret)
+			return ret;
+	}
+
+	return imx_ocotp ? 0 : -EPROBE_DEFER;
+}
+
 static struct driver imx_ocotp_driver = {
 	.name	= "imx_ocotp",
 	.probe	= imx_ocotp_probe,
diff --git a/include/mach/imx/ocotp.h b/include/mach/imx/ocotp.h
index 7c72edfb22a7..5f7b88f716a7 100644
--- a/include/mach/imx/ocotp.h
+++ b/include/mach/imx/ocotp.h
@@ -35,7 +35,7 @@
 int imx_ocotp_read_field(uint32_t field, unsigned *value);
 int imx_ocotp_write_field(uint32_t field, unsigned value);
 int imx_ocotp_permanent_write(int enable);
-bool imx_ocotp_sense_enable(bool enable);
+int imx_ocotp_sense_enable(bool enable);
 
 static inline u64 imx_ocotp_read_uid(void __iomem *ocotp)
 {
-- 
2.39.2