i2c: tegra: Make tegra_i2c_flush_fifos() usable in atomic transfer

The tegra_i2c_flush_fifos() shouldn't sleep in atomic transfer and jiffies
are not updating if interrupts are disabled. Let's switch to use iopoll
API helpers for register-polling. The iopoll API provides helpers for both
atomic and non-atomic cases.

Note that this patch doesn't fix any known problem because normally FIFO
is flushed at the time of starting a new transfer.
Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-tegra.c

@@ -470,9 +470,9 @@ static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
 
 static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
 {
-	unsigned long timeout = jiffies + HZ;
-	unsigned int offset;
-	u32 mask, val;
+	u32 mask, val, offset, reg_offset;
+	void __iomem *addr;
+	int err;
 
 	if (i2c_dev->hw->has_mst_fifo) {
 		mask = I2C_MST_FIFO_CONTROL_TX_FLUSH |
@@ -488,12 +488,19 @@ static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
 	val |= mask;
 	i2c_writel(i2c_dev, val, offset);
 
-	while (i2c_readl(i2c_dev, offset) & mask) {
-		if (time_after(jiffies, timeout)) {
-			dev_warn(i2c_dev->dev, "timeout waiting for fifo flush\n");
-			return -ETIMEDOUT;
-		}
-		usleep_range(1000, 2000);
+	reg_offset = tegra_i2c_reg_addr(i2c_dev, offset);
+	addr = i2c_dev->base + reg_offset;
+
+	if (i2c_dev->is_curr_atomic_xfer)
+		err = readl_relaxed_poll_timeout_atomic(addr, val, !(val & mask),
+							1000, 1000000);
+	else
+		err = readl_relaxed_poll_timeout(addr, val, !(val & mask),
+						 1000, 1000000);
+
+	if (err) {
+		dev_err(i2c_dev->dev, "failed to flush FIFO\n");
+		return err;
 	}
 	return 0;
 }