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From:   Bitan Biswas <bbiswas@nvidia.com>
To:     Laxman Dewangan <ldewangan@nvidia.com>,
        Thierry Reding <treding@nvidia.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        <linux-i2c@vger.kernel.org>, <linux-tegra@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, Peter Rosin <peda@axentia.se>,
        Wolfram Sang <wsa@the-dreams.de>,
        Dmitry Osipenko <digetx@gmail.com>
CC:     Shardar Mohammed <smohammed@nvidia.com>,
        Sowjanya Komatineni <skomatineni@nvidia.com>,
        Mantravadi Karthik <mkarthik@nvidia.com>,
        Bitan Biswas <bbiswas@nvidia.com>
Subject: [PATCH V5 6/7] i2c: tegra: fix PIO rx/tx residual transfer check
Date:   Tue, 11 Jun 2019 03:51:13 -0700
Message-ID: <1560250274-18499-6-git-send-email-bbiswas@nvidia.com>
In-Reply-To: <1560250274-18499-1-git-send-email-bbiswas@nvidia.com>
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Fix expression for residual bytes(less than word) transfer
in I2C PIO mode RX/TX.

Signed-off-by: Bitan Biswas <bbiswas@nvidia.com>
---
 drivers/i2c/busses/i2c-tegra.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 4dfb4c1..0596c12 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -514,7 +514,8 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
 	 * If there is a partial word at the end of buf, handle it manually to
 	 * prevent overwriting past the end of buf
 	 */
-	if (rx_fifo_avail > 0 && buf_remaining > 0) {
+	if (rx_fifo_avail > 0 &&
+	    (buf_remaining > 0 && buf_remaining < BYTES_PER_FIFO_WORD)) {
 		BUG_ON(buf_remaining > 3);
 		val = i2c_readl(i2c_dev, I2C_RX_FIFO);
 		val = cpu_to_le32(val);
@@ -557,11 +558,10 @@ 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
+		 * Update state before writing to FIFO.  If this causes 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.
+		 * not maskable).
 		 */
 		buf_remaining -= words_to_transfer * BYTES_PER_FIFO_WORD;
 		tx_fifo_avail -= words_to_transfer;
@@ -580,7 +580,8 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
 	 * prevent reading past the end of buf, which could cross a page
 	 * boundary and fault.
 	 */
-	if (tx_fifo_avail > 0 && buf_remaining > 0) {
+	if (tx_fifo_avail > 0 &&
+	    (buf_remaining > 0 && buf_remaining < BYTES_PER_FIFO_WORD)) {
 		BUG_ON(buf_remaining > 3);
 		memcpy(&val, buf, buf_remaining);
 		val = le32_to_cpu(val);
-- 
2.7.4