Subject: Re: [PATCH 3/5] i2c: aspeed: fix master pending state handling

From: Jae Hyun Yoo <[email-masked]>
Date: Tue, 8 Oct 2019 16:28:30 -0700

On 10/8/2019 4:15 PM, Tao Ren wrote:
> On 10/8/19 3:45 PM, Jae Hyun Yoo wrote:
>> Hi Tao,
>>
>> On 10/8/2019 3:00 PM, Tao Ren wrote:
>>> On 10/7/19 4:13 PM, Jae Hyun Yoo wrote:
>>>> In case of master pending state, it should not trigger the master
>>>> command because this H/W is sharing the same data buffer for slave
>>>> and master operations, so this commit fixes the issue with making
>>>> the master command triggering happen when the state goes to active
>>>> state.
>>>>
>>>> Signed-off-by: Jae Hyun Yoo <[email-masked]>
>>>> ---
>>>>    drivers/i2c/busses/i2c-aspeed.c | 9 +++++----
>>>>    1 file changed, 5 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
>>>> index fa66951b05d0..40f6cf98d32e 100644
>>>> --- a/drivers/i2c/busses/i2c-aspeed.c
>>>> +++ b/drivers/i2c/busses/i2c-aspeed.c
>>>> @@ -336,18 +336,19 @@ static void aspeed_i2c_do_start(struct aspeed_i2c_bus *bus)
>>>>        struct i2c_msg *msg = &bus->msgs[bus->msgs_index];
>>>>        u8 slave_addr = i2c_8bit_addr_from_msg(msg);
>>>>    -    bus->master_state = ASPEED_I2C_MASTER_START;
>>>> -
>>>>    #if IS_ENABLED(CONFIG_I2C_SLAVE)
>>>>        /*
>>>>         * If it's requested in the middle of a slave session, set the master
>>>>         * state to 'pending' then H/W will continue handling this master
>>>>         * command when the bus comes back to the idle state.
>>>>         */
>>>> -    if (bus->slave_state != ASPEED_I2C_SLAVE_INACTIVE)
>>>> +    if (bus->slave_state != ASPEED_I2C_SLAVE_INACTIVE) {
>>>>            bus->master_state = ASPEED_I2C_MASTER_PENDING;
>>>> +        return;
>>>> +    }
>>>>    #endif /* CONFIG_I2C_SLAVE */
>>>>    +    bus->master_state = ASPEED_I2C_MASTER_START;
>>>>        bus->buf_index = 0;
>>>>          if (msg->flags & I2C_M_RD) {
>>>> @@ -432,7 +433,7 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>>>>            if (bus->slave_state != ASPEED_I2C_SLAVE_INACTIVE)
>>>>                goto out_no_complete;
>>>>    -        bus->master_state = ASPEED_I2C_MASTER_START;
>>>> +        aspeed_i2c_do_start(bus);
>>>>        }
>>>
>>> Shall we move the restart-master logic from master_irq to bus_irq? The reason being:
>>> master transaction cannot be restarted when aspeed-i2c is running in slave state and
>>> receives STOP interrupt, because aspeed_i2c_master_irq won't be called in this case.
>>
>> Even in that case, master can be restarted properly because slave_irq
>> will be called first because master is in MASTER_PENDING state, so the
>> slave_irq handles the STOP interrupt as well, and then master_irq will
>> be called with SLAVE_INACTIVE state so the aspeed_i2c_do_start can be
>> called eventually.
> 
> I mean master_irq cannot be called when irq_remaining becomes 0 after slave_irq.

Ah, I see. It would be possibly happened. Probably we need to remove
'if (irq_remaining)' checking in bus_irq to make it call irqs always.
Will fix the issue in the next round.

Thanks,

Jae

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