i2c: tegra: Create i2c_writesl_vi() to use with VI I2C for filling TX FIFO

VI I2C controller has known hardware bug where immediate multiple
writes to TX_FIFO register gets stuck.

Recommended software work around is to read I2C register after
each write to TX_FIFO register to flush out the data.

This patch implements this work around for VI I2C controller.

Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 0727383f4940274b277c0d48bdba6bf3d42bb25c..8b113ae32dc713f26d28726a934a30c9f3b55863 100644 (file)
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -326,6 +326,8 @@ static void i2c_writel(struct tegra_i2c_dev *i2c_dev, u32 val, unsigned int reg)
        /* read back register to make sure that register writes completed */
        if (reg != I2C_TX_FIFO)
                readl_relaxed(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));
+       else if (i2c_dev->is_vi)
+               readl_relaxed(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, I2C_INT_STATUS));
 }
 
 static u32 i2c_readl(struct tegra_i2c_dev *i2c_dev, unsigned int reg)
@@ -339,6 +341,21 @@ static void i2c_writesl(struct tegra_i2c_dev *i2c_dev, void *data,
        writesl(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg), data, len);
 }
 
+static void i2c_writesl_vi(struct tegra_i2c_dev *i2c_dev, void *data,
+                          unsigned int reg, unsigned int len)
+{
+       u32 *data32 = data;
+
+       /*
+        * VI I2C controller has known hardware bug where writes get stuck
+        * when immediate multiple writes happen to TX_FIFO register.
+        * Recommended software work around is to read I2C register after
+        * each write to TX_FIFO register to flush out the data.
+        */
+       while (len--)
+               i2c_writel(i2c_dev, *data32++, reg);
+}
+
 static void i2c_readsl(struct tegra_i2c_dev *i2c_dev, void *data,
                       unsigned int reg, unsigned int len)
 {
@@ -811,7 +828,10 @@ 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);
+               if (i2c_dev->is_vi)
+                       i2c_writesl_vi(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer);
+               else
+                       i2c_writesl(i2c_dev, buf, I2C_TX_FIFO, words_to_transfer);
 
                buf += words_to_transfer * BYTES_PER_FIFO_WORD;
        }