23.07.2020 15:18, Krishna Yarlagadda пишет:
> In chips earlier to Tegra186, register write gets buffered. So to make
> sure register writes are completed, there is need to readback the
> register. Adding flag to disable this readback for Tegra186 and later
> chips.
>
> Signed-off-by: Krishna Yarlagadda <kyarlaga...@nvidia.com>
> ---
> drivers/i2c/busses/i2c-tegra.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index a841d6c..bdbbca0 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -220,6 +220,7 @@ struct tegra_i2c_hw_feature {
> bool has_mst_fifo;
> const struct i2c_adapter_quirks *quirks;
> bool supports_bus_clear;
> + bool has_reg_write_buffering;
> bool has_apb_dma;
> u8 tlow_std_mode;
> u8 thigh_std_mode;
> @@ -325,8 +326,11 @@ static void i2c_writel(struct tegra_i2c_dev *i2c_dev,
> u32 val,
> writel_relaxed(val, i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, 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));
> + if (i2c_dev->hw->has_reg_write_buffering) {
> + if (reg != I2C_TX_FIFO)
Should be single line.
What problem does this solve? If there is no visible effect, then please
drop this patch.
> + readl_relaxed(i2c_dev->base +
> + tegra_i2c_reg_addr(i2c_dev, reg));
> + }
