mfd: Restore wm8994 pin configuration after reset during suspend

Ensure that we leave the device with the pins in the expected
configuration if we leave it in reset over suspend, avoiding any
interoperation problems with other devices in the system.

Signed-off-by: Chris Rattray <crattray@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/wm8994-core.c

@@ -196,6 +196,7 @@ static int wm8994_suspend(struct device *dev)
 {
 	struct wm8994 *wm8994 = dev_get_drvdata(dev);
 	int ret;
+	int gpio_regs[WM8994_NUM_GPIO_REGS];
 
 	/* Don't actually go through with the suspend if the CODEC is
 	 * still active (eg, for audio passthrough from CP. */
@@ -277,12 +278,24 @@ static int wm8994_suspend(struct device *dev)
 				WM8994_LDO1ENA_PD | WM8994_LDO2ENA_PD,
 				WM8994_LDO1ENA_PD | WM8994_LDO2ENA_PD);
 
+	/* Save GPIO registers before reset */
+	regmap_bulk_read(wm8994->regmap, WM8994_GPIO_1, gpio_regs,
+			 WM8994_NUM_GPIO_REGS);
+
 	/* Explicitly put the device into reset in case regulators
 	 * don't get disabled in order to ensure consistent restart.
 	 */
 	wm8994_reg_write(wm8994, WM8994_SOFTWARE_RESET,
 			 wm8994_reg_read(wm8994, WM8994_SOFTWARE_RESET));
 
+	/* Restore GPIO registers to prevent problems with mismatched
+	 * pin configurations.
+	 */
+	ret = regmap_bulk_write(wm8994->regmap, WM8994_GPIO_1, gpio_regs,
+				WM8994_NUM_GPIO_REGS);
+	if (ret != 0)
+		dev_err(dev, "Failed to restore GPIO registers: %d\n", ret);
+
 	regcache_cache_only(wm8994->regmap, true);
 	regcache_mark_dirty(wm8994->regmap);