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From:   Sowjanya Komatineni <skomatineni@nvidia.com>
To:     <thierry.reding@gmail.com>, <jonathanh@nvidia.com>,
        <digetx@gmail.com>, <skomatineni@nvidia.com>
CC:     <linux-tegra@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-i2c@vger.kernel.org>
Subject: [PATCH v1] i2c: tegra: Fix i2c_writesl() to use writel() instead of writesl()
Date:   Mon, 19 Oct 2020 21:03:54 -0700
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VI I2C don't have DMA support and uses PIO mode all the time.

Current driver uses writesl() to fill TX FIFO based on available
empty slots and with this seeing strange silent hang during any I2C
register access after filling TX FIFO with 8 words.

Using writel() followed by i2c_readl() in a loop to write all words
to TX FIFO instead of using writesl() helps for large transfers in
PIO mode.

So, this patch updates i2c_writesl() API to use writel() in a loop
instead of writesl().

Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
---
 drivers/i2c/busses/i2c-tegra.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 6f08c0c..274bf3a 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -333,10 +333,13 @@ static u32 i2c_readl(struct tegra_i2c_dev *i2c_dev, unsigned int reg)
 	return readl_relaxed(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));
 }
 
-static void i2c_writesl(struct tegra_i2c_dev *i2c_dev, void *data,
+static void i2c_writesl(struct tegra_i2c_dev *i2c_dev, u32 *data,
 			unsigned int reg, unsigned int len)
 {
-	writesl(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg), data, len);
+	while (len--) {
+		writel(*data++, i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));
+		i2c_readl(i2c_dev, I2C_INT_STATUS);
+	}
 }
 
 static void i2c_readsl(struct tegra_i2c_dev *i2c_dev, void *data,
@@ -811,7 +814,7 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
 		i2c_dev->msg_buf_remaining = buf_remaining;
 		i2c_dev->msg_buf = buf + words_to_transfer * BYTES_PER_FIFO_WORD;
 
-		i2c_writesl(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer);
+		i2c_writesl(i2c_dev, (u32 *)buf, I2C_TX_FIFO, words_to_transfer);
 
 		buf += words_to_transfer * BYTES_PER_FIFO_WORD;
 	}
-- 
2.7.4