linux-kernel - Re: [PATCH v3] i2c: tegra: Create i2c_writesl_vi() to use with VI I2C for filling TX FIFO

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Date:   Tue, 12 Jan 2021 22:17:08 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, wsa@...-dreams.de
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-i2c@...r.kernel.org
Subject: Re: [PATCH v3] i2c: tegra: Create i2c_writesl_vi() to use with VI I2C
 for filling TX FIFO

12.01.2021 22:02, Sowjanya Komatineni пишет:
> 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.

You could have kept Thierry's ack since it was given to the fix in
general. No need to make v4.

> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 22 +++++++++++++++++++++-
>  1 file changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 6f08c0c..4a27782 100644
> --- 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;
>  	}
> 

Reviewed-by: Dmitry Osipenko <digetx@...il.com>