[PATCH 4/8] pwm: axi-pwmgen: Enable clocks before accessing hardware registers in probe()

[Lee Jones <lee@kernel.org>]

axi_pwmgen_probe() calls axi_pwmgen_setup(), which reads and writes MMIO
registers to verify the IP core version and determine the channel count,
before acquiring and enabling axi_clk.  If the bootloader leaves the AXI
peripheral clock gated, accessing the registers causes an unclocked bus
access fault.

Acquire and enable the clocks before calling axi_pwmgen_setup().

Fixes: 41814fe5c782 ("pwm: Add driver for AXI PWM generator")
Closes: https://sashiko.dev/#/bug/linux-bc988dbc-7b12-4785-a164-b6dcab29b86a
Cc: stable@vger.kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>
---
 drivers/pwm/pwm-axi-pwmgen.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/pwm/pwm-axi-pwmgen.c b/drivers/pwm/pwm-axi-pwmgen.c
index b40522f01002..7c1b38124787 100644
--- a/drivers/pwm/pwm-axi-pwmgen.c
+++ b/drivers/pwm/pwm-axi-pwmgen.c
@@ -270,16 +270,6 @@ static int axi_pwmgen_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, PTR_ERR(regmap),
 				     "failed to init register map\n");
 
-	ret = axi_pwmgen_setup(regmap, dev);
-	if (ret < 0)
-		return ret;
-
-	chip = devm_pwmchip_alloc(dev, ret, sizeof(*ddata));
-	if (IS_ERR(chip))
-		return PTR_ERR(chip);
-	ddata = pwmchip_get_drvdata(chip);
-	ddata->regmap = regmap;
-
 	/*
 	 * Using NULL here instead of "axi" for backwards compatibility. There
 	 * are some dtbs that don't give clock-names and have the "ext" clock
@@ -305,6 +295,16 @@ static int axi_pwmgen_probe(struct platform_device *pdev)
 	if (ret)
 		return dev_err_probe(dev, ret, "failed to get exclusive rate\n");
 
+	ret = axi_pwmgen_setup(regmap, dev);
+	if (ret < 0)
+		return ret;
+
+	chip = devm_pwmchip_alloc(dev, ret, sizeof(*ddata));
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+	ddata = pwmchip_get_drvdata(chip);
+	ddata->regmap = regmap;
+
 	ddata->clk_rate_hz = clk_get_rate(clk);
 	if (!ddata->clk_rate_hz || ddata->clk_rate_hz > NSEC_PER_SEC)
 		return dev_err_probe(dev, -EINVAL,
Cc: Drew Fustini <dfustini@baylibre.com>
-- 
2.56.0.398.g882cbad275-goog