Re: [PATCH] i2c: designware: fix slave omitted IC_INTR_STOP_DET

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi

On 10/14/20 8:25 AM, Michael Wu wrote:
When an I2C slave works, sometimes both IC_INTR_RX_FULL and
IC_INTR_STOP_DET are rising during an IRQ handle, especially when system
is busy or too late to handle interrupts.

If IC_INTR_RX_FULL is rising and the system doesn't handle immediately,
IC_INTR_STOP_DET may be rising and the system has to handle these two
events. For this there may be two problems:
e
1. IC_INTR_STOP_DET is rising after i2c_dw_read_clear_intrbits_slave()
    done: It seems invalidated because WRITE_REQUESTED is done after the
    1st WRITE_RECEIVED.

$ i2cset -f -y 2 0x42 0x00 0x41; dmesg -c
[0][clear_intrbits]0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
[1][irq_handler   ]0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
WRITE_RECEIVED
[0][clear_intrbits]0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
[1][irq_handler   ]0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x714 : INTR_STAT=0x204
WRITE_REQUESTED
WRITE_RECEIVED
[0][clear_intrbits]0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x710 : INTR_STAT=0x200
[1][irq_handler   ]0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x510 : INTR_STAT=0x0
STOP
[2][clear_intrbits]0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x510 : INTR_STAT=0x0

   t1: ISR with the 1st IC_INTR_RX_FULL.
   t2: Clear listed IC_INTR bits by i2c_dw_read_clear_intrbits_slave().
   t3: Enter i2c_dw_irq_handler_slave() and then do
       i2c_slave_event(WRITE_RECEIVED) because
       if (stat & DW_IC_INTR_RX_FULL).
   t4: ISR with the 2nd IC_INTR_RX_FULL.
   t5: Clear listed IC_INTR bits by i2c_dw_read_clear_intrbits_slave(),
       while IC_INTR_STOP_DET has not risen yet.
   t6: Enter i2c_dw_irq_handler_slave() and then IC_INTR_STOP_DET is
       rising. i2c_slave_event(WRITE_REQUESTED) will be done first because
       if ((stat & DW_IC_INTR_RX_FULL) && (stat & DW_IC_INTR_STOP_DET)) and
       then doing i2c_slave_event(WRITE_RECEIVED).
   t7: do i2c_slave_event(STOP) due to IC_INTR_STOP_DET not be cleared yet.

2. Both IC_INTR_STOP_DET and IC_INTR_RX_FULL are rising before
    i2c_dw_read_clear_intrbits_slave(): STOP cannot wait because
    IC_INTR_STOP_DET is cleared by i2c_dw_read_clear_intrbits_slave().

$ i2cset -f -y 2 0x42 0x00 0x41; dmesg -c
[0][clear_intrbits]0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
[1][irq_handler   ]0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
WRITE_RECEIVED
[0][clear_intrbits]0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x714 : INTR_STAT=0x204
[1][irq_handler   ]0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
WRITE_RECEIVED

   t1: ISR with the 1st IC_INTR_RX_FULL.
   t2: Clear listed IC_INTR bits by i2c_dw_read_clear_intrbits_slave().
   t3: Enter i2c_dw_irq_handler_slave() and then do
       i2c_slave_event(WRITE_RECEIVED) because
       if (stat & DW_IC_INTR_RX_FULL).
   t4: ISR with both IC_INTR_STOP_DET and the 2nd IC_INTR_RX_FULL.
   t5: Clear listed IC_INTR bits by i2c_dw_read_clear_intrbits_slave(). The
       current IC_INTR_STOP_DET is cleared by this
       i2c_dw_read_clear_intrbits_slave().
   t6: Enter i2c_dw_irq_handler_slave() and then do
       i2c_slave_event(WRITE_RECEIVED) because
       if (stat & DW_IC_INTR_RX_FULL).
   t7: i2c_slave_event(STOP) never be done because IC_INTR_STOP_DET was
       cleared in t5.

In order to resolve these problems, i2c_dw_read_clear_intrbits_slave()
should be called only one time in ISR and take the returned stat to handle
those occurred events.

Signed-off-by: Michael Wu <michael.wu@xxxxxxxxxx>
---
  drivers/i2c/busses/i2c-designware-slave.c | 79 ++++++++++++-----------
  1 file changed, 40 insertions(+), 39 deletions(-)

Thanks for the patch. I was thinking this too after your report but haven't found actually time to look at implementing it.

But what I was thinking it is probably good to have two patches. First patch that changes only i2c_dw_read_clear_intrbits_slave() semantics so that it's called only once like here and second patch that does other logic changes. Makes easier to catch possible regressions I think.

Jarkko




[Index of Archives]     [Linux GPIO]     [Linux SPI]     [Linux Hardward Monitoring]     [LM Sensors]     [Linux USB Devel]     [Linux Media]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux