[PATCH v3] mfd: arizona: Don't use regmap_read_poll_timeout

[Charles Keepax <ckeepax@opensource.cirrus.com>]

Some Arizona CODECs have a small timing window where they will
NAK an I2C transaction if it happens before the boot done bit is
set. This can cause the read of the register containing the boot
done bit to fail until it is set. Since regmap_read_poll_timeout
will abort polling if a read fails it can't be reliably used to
poll the boot done bit over I2C.

Do a partial revert of ef84f885e037 ("mfd: arizona: Refactor
arizona_poll_reg"), removing the regmap_read_poll_timeout but
leaving the refactoring to make the arizona_poll_reg take more
sensible arguments.

Fixes: ef84f885e037 ("mfd: arizona: Refactor arizona_poll_reg")
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
---

Changes since v2:
 - Refactor to remove initialisation of ret variable

Thanks,
Charles

 drivers/mfd/arizona-core.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/mfd/arizona-core.c b/drivers/mfd/arizona-core.c
index 83f1c5a516d99..5f1e37d23943a 100644
--- a/drivers/mfd/arizona-core.c
+++ b/drivers/mfd/arizona-core.c
@@ -24,6 +24,7 @@
 #include <linux/regulator/consumer.h>
 #include <linux/regulator/machine.h>
 #include <linux/slab.h>
+#include <linux/ktime.h>
 #include <linux/platform_device.h>
 
 #include <linux/mfd/arizona/core.h>
@@ -236,22 +237,39 @@ static irqreturn_t arizona_overclocked(int irq, void *data)
 
 #define ARIZONA_REG_POLL_DELAY_US 7500
 
+static inline bool arizona_poll_reg_delay(ktime_t timeout)
+{
+	if (ktime_compare(ktime_get(), timeout) > 0)
+		return false;
+
+	usleep_range(ARIZONA_REG_POLL_DELAY_US / 2, ARIZONA_REG_POLL_DELAY_US);
+
+	return true;
+}
+
 static int arizona_poll_reg(struct arizona *arizona,
 			    int timeout_ms, unsigned int reg,
 			    unsigned int mask, unsigned int target)
 {
+	ktime_t timeout = ktime_add_us(ktime_get(), timeout_ms * USEC_PER_MSEC);
 	unsigned int val = 0;
 	int ret;
 
-	ret = regmap_read_poll_timeout(arizona->regmap,
-				       reg, val, ((val & mask) == target),
-				       ARIZONA_REG_POLL_DELAY_US,
-				       timeout_ms * 1000);
-	if (ret)
-		dev_err(arizona->dev, "Polling reg 0x%x timed out: %x\n",
-			reg, val);
+	do {
+		ret = regmap_read(arizona->regmap, reg, &val);
 
-	return ret;
+		if ((val & mask) == target)
+			return 0;
+	} while (arizona_poll_reg_delay(timeout));
+
+	if (ret) {
+		dev_err(arizona->dev, "Failed polling reg 0x%x: %d\n",
+			reg, ret);
+		return ret;
+	}
+
+	dev_err(arizona->dev, "Polling reg 0x%x timed out: %x\n", reg, val);
+	return -ETIMEDOUT;
 }
 
 static int arizona_wait_for_boot(struct arizona *arizona)
-- 
2.11.0