On 4/13/21 2:58 PM, Wolfram Sang wrote:
> On Thu, Apr 08, 2021 at 04:00:00AM +0200, Marek Behún wrote:
>> I noticed a weird bug with this driver on Marvell CN9130 Customer
>> Reference Board.
>>
>> Sometime after boot, the system locks with the following message:
>> [104.071363] i2c i2c-0: mv64xxx: I2C bus locked, block: 1, time_left: 0
>>
>> The system does not respond afterwards, only warns about RCU stalls.
>>
>> This first appeared with commit e5c02cf54154 ("i2c: mv64xxx: Add runtime
>> PM support").
>>
>> With further experimentation I discovered that adding a delay into
>> mv64xxx_i2c_hw_init() fixes this issue. This function is called before
>> every xfer, due to how runtime PM works in this driver. It seems that in
>> order to work correctly, a delay is needed after the bus is reset in
>> this function.
>>
>> Since there already is a known erratum with this controller needing a
>> delay, I assume that this is just another place this needs to be
>> applied. Therefore I apply the delay only if errata_delay is true.
>>
>> Signed-off-by: Marek Behún <kabel@xxxxxxxxxx>
>
> Gregory? Looks reasonable to me and if so, we should have this in 5.12
> already. Comments from others are welcome, too, of course.
I also don't have an affected platform, so I did not notice this when adding
runtime PM. The change makes sense to me as well.
Reviewed-by: Samuel Holland <samuel@xxxxxxxxxxxx>
Cheers,
Samuel
>> ---
>> drivers/i2c/busses/i2c-mv64xxx.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/i2c/busses/i2c-mv64xxx.c b/drivers/i2c/busses/i2c-mv64xxx.c
>> index c590d36b5fd1..5c8e94b6cdb5 100644
>> --- a/drivers/i2c/busses/i2c-mv64xxx.c
>> +++ b/drivers/i2c/busses/i2c-mv64xxx.c
>> @@ -221,6 +221,10 @@ mv64xxx_i2c_hw_init(struct mv64xxx_i2c_data *drv_data)
>> writel(0, drv_data->reg_base + drv_data->reg_offsets.ext_addr);
>> writel(MV64XXX_I2C_REG_CONTROL_TWSIEN | MV64XXX_I2C_REG_CONTROL_STOP,
>> drv_data->reg_base + drv_data->reg_offsets.control);
>> +
>> + if (drv_data->errata_delay)
>> + udelay(5);
>> +
>> drv_data->state = MV64XXX_I2C_STATE_IDLE;
>> }
>>
>> --
>> 2.26.2
>>
