linux-kernel - Re: [PATCH] i2c: tegra: Wait for config load atomically while in ISR

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Date:   Mon, 11 Jan 2021 18:14:58 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Mikko Perttunen <mperttunen@...dia.com>, ldewangan@...dia.com,
        thierry.reding@...il.com, jonathanh@...dia.com, wsa@...nel.org
Cc:     linux-i2c@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] i2c: tegra: Wait for config load atomically while in ISR

11.01.2021 16:55, Mikko Perttunen пишет:
> Upon a communication error, the interrupt handler can call
> tegra_i2c_disable_packet_mode. This causes a sleeping poll to happen
> unless the current transaction was marked atomic. Since
> tegra_i2c_disable_packet_mode is only called from the interrupt path,
> make it use atomic waiting always.
> 
> Fixes: ede2299f7101 ("i2c: tegra: Support atomic transfers")
> Cc: stable@...r.kernel.org
> Signed-off-by: Mikko Perttunen <mperttunen@...dia.com>
> ---
> This fixes constant spew for me while HDMI is connected to a
> powered off television.
> 
>  drivers/i2c/busses/i2c-tegra.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 6f08c0c3238d..4a7ff1840565 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -528,12 +528,12 @@ static void tegra_i2c_vi_init(struct tegra_i2c_dev *i2c_dev)
>  
>  static int tegra_i2c_poll_register(struct tegra_i2c_dev *i2c_dev,
>  				   u32 reg, u32 mask, u32 delay_us,
> -				   u32 timeout_us)
> +				   u32 timeout_us, bool force_atomic)
>  {
>  	void __iomem *addr = i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg);
>  	u32 val;
>  
> -	if (!i2c_dev->atomic_mode)
> +	if (!i2c_dev->atomic_mode && !force_atomic)
>  		return readl_relaxed_poll_timeout(addr, val, !(val & mask),
>  						  delay_us, timeout_us);
>  
> @@ -560,7 +560,7 @@ static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
>  	val |= mask;
>  	i2c_writel(i2c_dev, val, offset);
>  
> -	err = tegra_i2c_poll_register(i2c_dev, offset, mask, 1000, 1000000);
> +	err = tegra_i2c_poll_register(i2c_dev, offset, mask, 1000, 1000000, false);
>  	if (err) {
>  		dev_err(i2c_dev->dev, "failed to flush FIFO\n");
>  		return err;
> @@ -569,7 +569,7 @@ static int tegra_i2c_flush_fifos(struct tegra_i2c_dev *i2c_dev)
>  	return 0;
>  }
>  
> -static int tegra_i2c_wait_for_config_load(struct tegra_i2c_dev *i2c_dev)
> +static int tegra_i2c_wait_for_config_load(struct tegra_i2c_dev *i2c_dev, bool force_atomic)
>  {
>  	int err;
>  
> @@ -579,7 +579,7 @@ static int tegra_i2c_wait_for_config_load(struct tegra_i2c_dev *i2c_dev)
>  	i2c_writel(i2c_dev, I2C_MSTR_CONFIG_LOAD, I2C_CONFIG_LOAD);
>  
>  	err = tegra_i2c_poll_register(i2c_dev, I2C_CONFIG_LOAD, 0xffffffff,
> -				      1000, I2C_CONFIG_LOAD_TIMEOUT);
> +				      1000, I2C_CONFIG_LOAD_TIMEOUT, force_atomic);
>  	if (err) {
>  		dev_err(i2c_dev->dev, "failed to load config\n");
>  		return err;
> @@ -684,7 +684,7 @@ static int tegra_i2c_init(struct tegra_i2c_dev *i2c_dev)
>  	if (i2c_dev->multimaster_mode && i2c_dev->hw->has_slcg_override_reg)
>  		i2c_writel(i2c_dev, I2C_MST_CORE_CLKEN_OVR, I2C_CLKEN_OVERRIDE);
>  
> -	err = tegra_i2c_wait_for_config_load(i2c_dev);
> +	err = tegra_i2c_wait_for_config_load(i2c_dev, false);
>  	if (err)
>  		return err;
>  
> @@ -707,7 +707,7 @@ static int tegra_i2c_disable_packet_mode(struct tegra_i2c_dev *i2c_dev)
>  	if (cnfg & I2C_CNFG_PACKET_MODE_EN)
>  		i2c_writel(i2c_dev, cnfg & ~I2C_CNFG_PACKET_MODE_EN, I2C_CNFG);
>  
> -	return tegra_i2c_wait_for_config_load(i2c_dev);
> +	return tegra_i2c_wait_for_config_load(i2c_dev, true);
>  }
>  
>  static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
> @@ -1090,7 +1090,7 @@ static int tegra_i2c_issue_bus_clear(struct i2c_adapter *adap)
>  	      I2C_BC_TERMINATE;
>  	i2c_writel(i2c_dev, val, I2C_BUS_CLEAR_CNFG);
>  
> -	err = tegra_i2c_wait_for_config_load(i2c_dev);
> +	err = tegra_i2c_wait_for_config_load(i2c_dev, false);
>  	if (err)
>  		return err;
>  
> 

What about a simpler variant:

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 6f08c0c3238d..0727383f4940 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -533,7 +533,7 @@ static int tegra_i2c_poll_register(struct
tegra_i2c_dev *i2c_dev,
 	void __iomem *addr = i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg);
 	u32 val;

-	if (!i2c_dev->atomic_mode)
+	if (!i2c_dev->atomic_mode && !in_irq())
 		return readl_relaxed_poll_timeout(addr, val, !(val & mask),
 						  delay_us, timeout_us);