i2c: tegra: Wait for config load atomically while in ISR

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@vger.kernel.org
Signed-off-by: Mikko Perttunen <mperttunen@nvidia.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(-)

Agreed that this is possibly not optimal, but this patch simply returns 
the behavior to what it was before "i2c: tegra: Support atomic 
transfers", fixing the overt issue.

Design fixes can be considered later, in a non-stable patch.

Mikko

On 1/11/21 4:31 PM, David Laight wrote:
> From: Mikko Perttunen
>> Sent: 11 January 2021 13:56
>>
>> 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.
> 
> Spin-waiting in an ISR for anything that it makes sense to do
> a sleep-wait for at other times is badly broken design.
> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>

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@vger.kernel.org
> Signed-off-by: Mikko Perttunen <mperttunen@nvidia.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);