Re: [PATCH] i2c: bcm-iproc: Add i2c recovery support

[Ray Jui]

On 6/1/2021 2:44 PM, Chris Packham wrote:
> 
> On 2/06/21 9:03 am, Ray Jui wrote:
>>
>> On 5/30/2021 3:56 PM, Chris Packham wrote:
>>> From: Richard Laing <richard.laing@xxxxxxxxxxxxxxxxxxx>
>>>
>>> The bcm-iproc controller can put the SDA/SCL lines into bit-bang mode,
>>> make use of this to support i2c bus recovery.
>>>
>>> Signed-off-by: Richard Laing <richard.laing@xxxxxxxxxxxxxxxxxxx>
>>> Signed-off-by: Chris Packham <chris.packham@xxxxxxxxxxxxxxxxxxx>
>>> ---
>>>
>>> Notes:
>>>      Richard did most of the work on this. I'm just cleaning it up to get it
>>>      upstream.
>>>
>>>   drivers/i2c/busses/i2c-bcm-iproc.c | 115 +++++++++++++++++++++++++++++
>>>   1 file changed, 115 insertions(+)
>>>
>>> diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
>>> index cceaf69279a9..d63a286c1660 100644
>>> --- a/drivers/i2c/busses/i2c-bcm-iproc.c
>>> +++ b/drivers/i2c/busses/i2c-bcm-iproc.c
>>> @@ -26,6 +26,7 @@
>>>   #define CFG_RESET_SHIFT              31
>>>   #define CFG_EN_SHIFT                 30
>>>   #define CFG_SLAVE_ADDR_0_SHIFT       28
>>> +#define CFG_BIT_BANG_SHIFT           29
>> move this up one line (to be consistent with existing bit order)
> 
> Ack.
> 
>>>   #define CFG_M_RETRY_CNT_SHIFT        16
>>>   #define CFG_M_RETRY_CNT_MASK         0x0f
>>>   
>>> @@ -66,6 +67,12 @@
>>>   #define S_FIFO_RX_THLD_SHIFT         8
>>>   #define S_FIFO_RX_THLD_MASK          0x3f
>>>   
>>> +#define M_BB_CTRL_OFFSET             0x14
>>> +#define M_BB_SMBCLK_IN               31
>> M_BB_CTRL_CLK_IN_SHIFT, ket is to have '_SHIFT' to be consistent with
>> existing code
> 
> Ack.
> 
>>> +#define M_BB_SMBCLK_OUT_EN           30
>> M_BB_CTRL_CLK_OUT_SHIFT
>>
>>> +#define M_BB_SMBDAT_IN               29
>> M_BB_CTRL_DATA_IN_SHIFT
>>
>>> +#define M_BB_SMBDAT_OUT_EN           28
>> M_BB_CTRL_DATA_OUT_SHIFT
>>
>>> +
>>>   #define M_CMD_OFFSET                 0x30
>>>   #define M_CMD_START_BUSY_SHIFT       31
>>>   #define M_CMD_STATUS_SHIFT           25
>>> @@ -713,6 +720,112 @@ static void bcm_iproc_i2c_enable_disable(struct bcm_iproc_i2c_dev *iproc_i2c,
>>>   	iproc_i2c_wr_reg(iproc_i2c, CFG_OFFSET, val);
>>>   }
>>>   
>>> +static void bcm_iproc_i2c_reset(struct bcm_iproc_i2c_dev *iproc_i2c)
>>> +{
>>> +	u32 tmp;
>>> +
>>> +	tmp = readl(iproc_i2c->base + CFG_OFFSET);
>>> +	tmp |= BIT(CFG_RESET_SHIFT);
>>> +	writel(tmp, iproc_i2c->base + CFG_OFFSET);
>>> +	udelay(100);
>> This puts the controller in reset and hold it there, but never brings
>> the controller out of reset (bcm_iproc_i2c_init called in unprepare
>> brings the controller out of reset)
>>
>> Calling it a "reset" function is a bit misleading to me. My expectation
>> of a reset function is that you generate a reset pulse, ie.g., reset ->
>> delay -> out of reset.
>>
>> Why don't you simply put this seuquence of code in the prepare_recovery
>> function below, instead of calling this a reset function?
> 
> Will do. Should I also change the udelay(100) to a usleep_range(100, 
> 200)? Same question for the other uses of udelay().
> 

Sure I think that makes sense.

>>
>>> +
>>> +}
>>> +
>>> +static void bcm_iproc_i2c_prepare_recovery(struct i2c_adapter *adap)
>>> +{
>>> +	struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
>>> +	u32 tmp;
>>> +
>>> +	dev_dbg(iproc_i2c->device, "Prepare recovery\n");
>>> +
>>> +	/* Disable interrupts */
>>> +	writel(0, iproc_i2c->base + IE_OFFSET);
>>> +	readl(iproc_i2c->base + IE_OFFSET);
>>> +	synchronize_irq(iproc_i2c->irq);
>>> +
>>> +	bcm_iproc_i2c_reset(iproc_i2c);
>>> +
>>> +	/* Switch to bit-bang mode */
>>> +	tmp = readl(iproc_i2c->base + CFG_OFFSET);
>>> +	tmp |= BIT(CFG_BIT_BANG_SHIFT);
>>> +	writel(tmp, iproc_i2c->base + CFG_OFFSET);
>> add usleep_range(100, 200) here, required delay after switching to bit
>> bang based on spec.
> 
> Ack.
> 
>>
>>> +}
>>> +
>>> +static void bcm_iproc_i2c_unprepare_recovery(struct i2c_adapter *adap)
>>> +{
>>> +	struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
>>> +	u32 tmp;
>>> +
>>> +	/* Switch to normal mode */
>>> +	tmp = readl(iproc_i2c->base + CFG_OFFSET);
>>> +	tmp &= ~BIT(CFG_BIT_BANG_SHIFT);
>>> +	writel(tmp, iproc_i2c->base + CFG_OFFSET);
>>> +	udelay(100);
>>> +
>>> +	bcm_iproc_i2c_init(iproc_i2c);
>> Add sequence to re-configure to desired bus speed here after the reset
>> sequence (someone else in our team tested this is required to resume to
>> proper bus speed).
> bcm_iproc_i2c_resume() seems to have the exact sequence I need. If I 
> move it outside of CONFIG_PM_SLEEP I could just call it here.

Yes agree with you that 'bcm_iproc_i2c_resume' can be resued.

>>> +	bcm_iproc_i2c_enable_disable(iproc_i2c, true);
>>> +
>>> +	dev_dbg(iproc_i2c->device, "Recovery complete\n");
>>> +}
>>> +
>>> +static int bcm_iproc_i2c_get_scl(struct i2c_adapter *adap)
>>> +{
>>> +	struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
>>> +	u32 tmp;
>>> +
>>> +	tmp = readl(iproc_i2c->base + M_BB_CTRL_OFFSET);
>>> +
>>> +	return !!(tmp & BIT(M_BB_SMBCLK_IN));
>>> +}
>>> +
>>> +static void bcm_iproc_i2c_set_scl(struct i2c_adapter *adap, int val)
>>> +{
>>> +	struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
>>> +	u32 tmp;
>>> +
>>> +	tmp = readl(iproc_i2c->base + M_BB_CTRL_OFFSET);
>>> +	if (val)
>>> +		tmp |= BIT(M_BB_SMBCLK_OUT_EN);
>>> +	else
>>> +		tmp &= ~BIT(M_BB_SMBCLK_OUT_EN);
>>> +
>>> +	writel(tmp, iproc_i2c->base + M_BB_CTRL_OFFSET);
>>> +}
>>> +
>>> +static void bcm_iproc_i2c_set_sda(struct i2c_adapter *adap, int val)
>>> +{
>>> +	struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
>>> +	u32 tmp;
>>> +
>>> +	tmp = readl(iproc_i2c->base + M_BB_CTRL_OFFSET);
>>> +	if (val)
>>> +		tmp |= BIT(M_BB_SMBDAT_OUT_EN);
>>> +	else
>>> +		tmp &= ~BIT(M_BB_SMBDAT_OUT_EN);
>>> +
>>> +	writel(tmp, iproc_i2c->base + M_BB_CTRL_OFFSET);
>>> +}
>>> +
>>> +static int bcm_iproc_i2c_get_sda(struct i2c_adapter *adap)
>>> +{
>>> +	struct bcm_iproc_i2c_dev *iproc_i2c = i2c_get_adapdata(adap);
>>> +	u32 tmp;
>>> +
>>> +	tmp = readl(iproc_i2c->base + M_BB_CTRL_OFFSET);
>>> +
>>> +	return !!(tmp & BIT(M_BB_SMBDAT_IN));
>>> +}
>>> +
>>> +static struct i2c_bus_recovery_info bcm_iproc_recovery_info = {
>> static const struct ...
> Ack.
>>> +	.recover_bus = i2c_generic_scl_recovery,
>>> +	.prepare_recovery = bcm_iproc_i2c_prepare_recovery,
>>> +	.unprepare_recovery = bcm_iproc_i2c_unprepare_recovery,
>>> +	.set_scl = bcm_iproc_i2c_set_scl,
>>> +	.get_scl = bcm_iproc_i2c_get_scl,
>>> +	.set_sda = bcm_iproc_i2c_set_sda,
>>> +	.get_sda = bcm_iproc_i2c_get_sda,
>>> +};
>>> +
>>>   static int bcm_iproc_i2c_check_status(struct bcm_iproc_i2c_dev *iproc_i2c,
>>>   				      struct i2c_msg *msg)
>>>   {
>>> @@ -839,6 +952,7 @@ static int bcm_iproc_i2c_xfer_internal(struct bcm_iproc_i2c_dev *iproc_i2c,
>>>   	if (!!(iproc_i2c_rd_reg(iproc_i2c,
>>>   				M_CMD_OFFSET) & BIT(M_CMD_START_BUSY_SHIFT))) {
>>>   		dev_warn(iproc_i2c->device, "bus is busy\n");
>>> +		i2c_recover_bus(&iproc_i2c->adapter);
>> 'i2c_recover_bus' should not be ALWAYS called here. You don't know if
>> bus is actually locked up or it's other issues that caused this.
>>
>> We need a logic to detect and confirm the lock up condition before
>> committing to recover operation:
>>
>> /* Check if bus lockup occurred, and invoke recovery if so. */
>> static void iproc_i2c_lockup_recover(struct bcm_iproc_i2c_dev *iproc_i2c)
>> {
>> 	/*
>> 	 * assume bus lockup if SDA line is low;
>> 	 * note that there is no need to switch to
>> 	 * bit-bang mode for this check.
>> 	 */
>> 	if (!bcm_iproc_i2c_get_sda(&iproc_i2c->adapter)) {
>> 		/* locked up - invoke i2c bus recovery. */
>> 		int ret = i2c_recover_bus(&iproc_i2c->adapter);
>> 			if (ret)
>> 				dev_err(iproc_i2c->device,
>> 					"bus recovery: error %d\n",
>> 					ret);
>> 	}
>> }
>>
>> 'iproc_i2c_lockup_recover' should be called in two locations in the driver:
>>
>> 1. After 'transaction timed out' (and after flush both TX/RX FIFOS)
>> 2. After 'bcm_iproc_i2c_check_status' failures (and after flush both
>> TX/RX FIFOs).
> 
> I see bcm_iproc_i2c_check_status() has a "recovery" case on an unknown 
> error. Should I remove that if I'm going to call 
> iproc_i2c_lockup_recover() or check for ret != -EIO?
> 

You may leave that (as first level recovery due to some potential
internal ASIC issues).

Let iproc_i2c_lockup_recover handles the bus lockup type of recovery
(after confirming the bus is indeed locked up).

>>
>>>   		return -EBUSY;
>>>   	}
>>>   
>>> @@ -1111,6 +1225,7 @@ static int bcm_iproc_i2c_probe(struct platform_device *pdev)
>>>   		of_node_full_name(iproc_i2c->device->of_node));
>>>   	adap->algo = &bcm_iproc_algo;
>>>   	adap->quirks = &bcm_iproc_i2c_quirks;
>>> +	adap->bus_recovery_info = &bcm_iproc_recovery_info;
>>>   	adap->dev.parent = &pdev->dev;
>>>   	adap->dev.of_node = pdev->dev.of_node;
>>>   
>>>
>> Thanks,
>>
>> Ray

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