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[v9,17/32] i2c: tegra: Remove outdated barrier()

Message ID 20200929221915.10979-18-digetx@gmail.com
State Superseded
Headers show
Series Improvements for Tegra I2C driver | expand

Commit Message

Dmitry Osipenko Sept. 29, 2020, 10:19 p.m. UTC 
The barrier() was intended to reduce possibility of racing with the
interrupt handler, but driver's code evolved significantly and today's
driver enables interrupt only when it waits for completion notification.
Hence barrier() has no good use anymore, let's remove it.

Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Tested-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/i2c/busses/i2c-tegra.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)
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Patch

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index a56c0873f4a3..347651401cd6 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -795,18 +795,17 @@  static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
 			words_to_transfer = tx_fifo_avail;
 
 		/*
-		 * Update state before writing to FIFO.  If this casues us
-		 * to finish writing all bytes (AKA buf_remaining goes to 0) we
-		 * have a potential for an interrupt (PACKET_XFER_COMPLETE is
-		 * not maskable).  We need to make sure that the isr sees
-		 * buf_remaining as 0 and doesn't call us back re-entrantly.
+		 * Update state before writing to FIFO.  Note that this may
+		 * cause us to finish writing all bytes (AKA buf_remaining
+		 * goes to 0), hence we have a potential for an interrupt
+		 * (PACKET_XFER_COMPLETE is not maskable), but GIC interrupt
+		 * is disabled at this point.
 		 */
 		buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;
 		tx_fifo_avail -= words_to_transfer;
 		i2c_dev->msg_buf_remaining = buf_remaining;
 		i2c_dev->msg_buf = buf +
 			words_to_transfer * BYTES_PER_FIFO_WORD;
-		barrier();
 
 		i2c_writesl(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer);
 
@@ -827,10 +826,8 @@  static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
 		memcpy(&val, buf, buf_remaining);
 		val = le32_to_cpu(val);
 
-		/* Again update before writing to FIFO to make sure isr sees. */
 		i2c_dev->msg_buf_remaining = 0;
 		i2c_dev->msg_buf = NULL;
-		barrier();
 
 		i2c_writel(i2c_dev, val, I2C_TX_FIFO);
 	}