linux-kernel - Re: [PATCH V1 6/6] i2c: tegra: remove BUG, BUG

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Date:   Fri, 7 Jun 2019 11:55:54 -0700
From:   Bitan Biswas <bbiswas@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Thierry Reding <treding@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        <linux-i2c@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Peter Rosin <peda@...ntia.se>,
        Wolfram Sang <wsa@...-dreams.de>
CC:     Shardar Mohammed <smohammed@...dia.com>,
        Sowjanya Komatineni <skomatineni@...dia.com>,
        Mantravadi Karthik <mkarthik@...dia.com>
Subject: Re: [PATCH V1 6/6] i2c: tegra: remove BUG, BUG_ON



On 6/7/19 5:18 AM, Dmitry Osipenko wrote:
> 07.06.2019 15:12, Dmitry Osipenko пишет:
>> 07.06.2019 15:08, Dmitry Osipenko пишет:
>>> 07.06.2019 14:55, Bitan Biswas пишет:
>>>> Remove redundant BUG_ON calls or replace with WARN_ON_ONCE
>>>> as needed. Replace BUG() with error handling code.
>>>> Define I2C_ERR_UNEXPECTED_STATUS for error handling.
>>>>
>>>> Signed-off-by: Bitan Biswas <bbiswas@...dia.com>
>>>> ---
>>>>   drivers/i2c/busses/i2c-tegra.c | 15 ++++++++-------
>>>>   1 file changed, 8 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
>>>> index 4dfb4c1..c407bd7 100644
>>>> --- a/drivers/i2c/busses/i2c-tegra.c
>>>> +++ b/drivers/i2c/busses/i2c-tegra.c
>>>> @@ -73,6 +73,7 @@
>>>>   #define I2C_ERR_NO_ACK				BIT(0)
>>>>   #define I2C_ERR_ARBITRATION_LOST		BIT(1)
>>>>   #define I2C_ERR_UNKNOWN_INTERRUPT		BIT(2)
>>>> +#define I2C_ERR_UNEXPECTED_STATUS		BIT(3)
>>>>   
>>>>   #define PACKET_HEADER0_HEADER_SIZE_SHIFT	28
>>>>   #define PACKET_HEADER0_PACKET_ID_SHIFT		16
>>>> @@ -515,7 +516,6 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
>>>>   	 * prevent overwriting past the end of buf
>>>>   	 */
>>>>   	if (rx_fifo_avail > 0 && buf_remaining > 0) {
>>>> -		BUG_ON(buf_remaining > 3);
>>>>   		val = i2c_readl(i2c_dev, I2C_RX_FIFO);
>>>>   		val = cpu_to_le32(val);
>>>>   		memcpy(buf, &val, buf_remaining);
>>>> @@ -523,7 +523,6 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
>>>>   		rx_fifo_avail--;
>>>>   	}
>>>>   
>>>> -	BUG_ON(rx_fifo_avail > 0 && buf_remaining > 0);
>>>>   	i2c_dev->msg_buf_remaining = buf_remaining;
>>>>   	i2c_dev->msg_buf = buf;
>>>>   
>>>> @@ -581,7 +580,6 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
>>>>   	 * boundary and fault.
>>>>   	 */
>>>>   	if (tx_fifo_avail > 0 && buf_remaining > 0) {
>>>> -		BUG_ON(buf_remaining > 3);
>>>>   		memcpy(&val, buf, buf_remaining);
>>>>   		val = le32_to_cpu(val);
>>>>   
>>>> @@ -847,10 +845,13 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
>>>>   
>>>>   	if (!i2c_dev->is_curr_dma_xfer) {
>>>>   		if (i2c_dev->msg_read && (status & I2C_INT_RX_FIFO_DATA_REQ)) {
>>>> -			if (i2c_dev->msg_buf_remaining)
>>>> +			if (i2c_dev->msg_buf_remaining) {
>>>>   				tegra_i2c_empty_rx_fifo(i2c_dev);
>>>> -			else
>>>> -				BUG();
>>>> +			} else {
>>>> +				dev_err(i2c_dev->dev, "unexpected rx data request\n");
>>>> +				i2c_dev->msg_err |= I2C_ERR_UNEXPECTED_STATUS;
>>>> +				goto err;
>>>> +			}
>>>>   		}
>>>>   
>>>>   		if (!i2c_dev->msg_read && (status & I2C_INT_TX_FIFO_DATA_REQ)) {
>>>> @@ -876,7 +877,7 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)
>>>>   	if (status & I2C_INT_PACKET_XFER_COMPLETE) {
>>>>   		if (i2c_dev->is_curr_dma_xfer)
>>>>   			i2c_dev->msg_buf_remaining = 0;
>>>> -		BUG_ON(i2c_dev->msg_buf_remaining);
>>>> +		WARN_ON_ONCE(i2c_dev->msg_buf_remaining);
>>>>   		complete(&i2c_dev->msg_complete);
>>>>   	}
>>>>   	goto done;
>>>>
>>>
>>> Very nice, thank you very much! BTW, I think it may worth to add another
>>> patch that will reset hardware state in a case of the warning since we
>>> know that something gone wrong.
>>>
>>> Reviewed-by: Dmitry Osipenko <digetx@...il.com>
>>>
>>
>> Something like that:
>>
>>   	complete(&i2c_dev->msg_complete);
>>
>> 	if (WARN_ON_ONCE(i2c_dev->msg_buf_remaining))
>> 		goto err;
>>
> 
> Ah, that's inside the ISR, so maybe will make sense to just not complete
> the transfer and let it timeout:
> 
> 	if (!WARN_ON_ONCE(i2c_dev->msg_buf_remaining))
> 		complete(&i2c_dev->msg_complete);
OK. I shall send the updated patch.

-Thanks,
  Bitan