linux-kernel - Re: [PATCH i2c-next v6] i2c: aspeed: Handle master/slave combined irq events properly

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Message-ID: <3f86e75f-1502-eae8-0633-d087937111c8@roeck-us.net>
Date:   Thu, 13 Sep 2018 06:33:29 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Cédric Le Goater <clg@...d.org>,
        Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>
Cc:     Joel Stanley <joel@....id.au>, linux-aspeed@...ts.ozlabs.org,
        Vernon Mauery <vernon.mauery@...ux.intel.com>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-i2c@...r.kernel.org, jarkko.nikula@...ux.intel.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        James Feist <james.feist@...ux.intel.com>
Subject: Re: [PATCH i2c-next v6] i2c: aspeed: Handle master/slave combined irq
 events properly

On 09/12/2018 10:45 PM, Cédric Le Goater wrote

[ ... ]

>> ---
>> qemu:
>>
>> diff --git a/hw/i2c/aspeed_i2c.c b/hw/i2c/aspeed_i2c.c
>> index c762c73..0d4aa08 100644
>> --- a/hw/i2c/aspeed_i2c.c
>> +++ b/hw/i2c/aspeed_i2c.c
>> @@ -180,6 +180,33 @@ static uint8_t aspeed_i2c_get_state(AspeedI2CBus *bus)
>>       return (bus->cmd >> I2CD_TX_STATE_SHIFT) & I2CD_TX_STATE_MASK;
>>   }
>>   
>> +static void aspeed_i2c_handle_rx_cmd(AspeedI2CBus *bus)
>> +{
>> +    int ret;
>> +
>> +    if (!(bus->cmd & (I2CD_M_RX_CMD | I2CD_M_S_RX_CMD_LAST))) {
>> +        return;
>> +    }
> 
> it deserves a comment to understand which scenario we are trying to handle.
> 
>> +    if (bus->intr_status & I2CD_INTR_RX_DONE) {
>> +        return;
>> +    }
> 
> should be handled in aspeed_i2c_bus_handle_cmd() I think
> 

I moved those two checks into the calling code.


>> +    aspeed_i2c_set_state(bus, I2CD_MRXD);
>> +    ret = i2c_recv(bus->bus);
>> +    if (ret < 0) {
>> +        qemu_log_mask(LOG_GUEST_ERROR, "%s: read failed\n", __func__);
>> +        ret = 0xff;
>> +    } else {
>> +        bus->intr_status |= I2CD_INTR_RX_DONE;
>> +    }
>> +    bus->buf = (ret & I2CD_BYTE_BUF_RX_MASK) << I2CD_BYTE_BUF_RX_SHIFT;
>> +    if (bus->cmd & I2CD_M_S_RX_CMD_LAST) {
>> +        i2c_nack(bus->bus);
>> +    }
>> +    bus->cmd &= ~(I2CD_M_RX_CMD | I2CD_M_S_RX_CMD_LAST);
>> +    aspeed_i2c_set_state(bus, I2CD_MACTIVE);
>> +}
>> +
>>   /*
>>    * The state machine needs some refinement. It is only used to track
>>    * invalid STOP commands for the moment.
>> @@ -188,7 +215,7 @@ static void aspeed_i2c_bus_handle_cmd(AspeedI2CBus *bus, uint64_t value)
>>   {
>>       bus->cmd &= ~0xFFFF;
>>       bus->cmd |= value & 0xFFFF;
>> -    bus->intr_status = 0;> +    bus->intr_status &= I2CD_INTR_RX_DONE;
> 
> it deserves a comment to understand which scenario we are trying to handle.
>    

Ok. FWIW, I wonder if intr_status should be touched here in the first place,
but I neither have the hardware nor a datasheet, so I don't know if any bits
are auto-cleared.

>>       if (bus->cmd & I2CD_M_START_CMD) {
>>           uint8_t state = aspeed_i2c_get_state(bus) & I2CD_MACTIVE ?
>> @@ -227,22 +254,7 @@ static void aspeed_i2c_bus_handle_cmd(AspeedI2CBus *bus, uint64_t value)
>>       }
>>   
>>       if (bus->cmd & (I2CD_M_RX_CMD | I2CD_M_S_RX_CMD_LAST)) {
>> -        int ret;
>> -
>> -        aspeed_i2c_set_state(bus, I2CD_MRXD);
>> -        ret = i2c_recv(bus->bus);
>> -        if (ret < 0) {
>> -            qemu_log_mask(LOG_GUEST_ERROR, "%s: read failed\n", __func__);
>> -            ret = 0xff;
>> -        } else {
>> -            bus->intr_status |= I2CD_INTR_RX_DONE;
>> -        }
>> -        bus->buf = (ret & I2CD_BYTE_BUF_RX_MASK) << I2CD_BYTE_BUF_RX_SHIFT;
>> -        if (bus->cmd & I2CD_M_S_RX_CMD_LAST) {
>> -            i2c_nack(bus->bus);
>> -        }
>> -        bus->cmd &= ~(I2CD_M_RX_CMD | I2CD_M_S_RX_CMD_LAST);
>> -        aspeed_i2c_set_state(bus, I2CD_MACTIVE);
>> +        aspeed_i2c_handle_rx_cmd(bus);
>>       }
>>   
>>       if (bus->cmd & I2CD_M_STOP_CMD) {
>> @@ -263,6 +275,7 @@ static void aspeed_i2c_bus_write(void *opaque, hwaddr offset,
>>                                    uint64_t value, unsigned size)
>>   {
>>       AspeedI2CBus *bus = opaque;
>> +    int status;
>>   
>>       switch (offset) {
>>       case I2CD_FUN_CTRL_REG:
>> @@ -283,9 +296,16 @@ static void aspeed_i2c_bus_write(void *opaque, hwaddr offset,
>>           bus->intr_ctrl = value & 0x7FFF;
>>           break;
>>       case I2CD_INTR_STS_REG:
>> +        status = bus->intr_status;
>>           bus->intr_status &= ~(value & 0x7FFF);
>> -        bus->controller->intr_status &= ~(1 << bus->id);
>> -        qemu_irq_lower(bus->controller->irq);
>> +        if (!bus->intr_status) {
>> +            bus->controller->intr_status &= ~(1 << bus->id);
>> +            qemu_irq_lower(bus->controller->irq);
>> +        }
> 
> That part below is indeed something to fix. I had a similar patch.
> 

Should I split it out as separate patch ? Alternatively, if you submitted
your patch already, I'll be happy to use it as base for mine.

Thanks,
Guenter

> 
>> +        if ((status & I2CD_INTR_RX_DONE) && !(bus->intr_status & I2CD_INTR_RX_DONE)) {
>> +            aspeed_i2c_handle_rx_cmd(bus);
>> +            aspeed_i2c_bus_raise_interrupt(bus);
>> +        }
> 
> ok.
> 
> Thanks for looking into this.
> 
> C.
> 
>>           break;
>>       case I2CD_DEV_ADDR_REG:
>>           qemu_log_mask(LOG_UNIMP, "%s: slave mode not implemented\n",
>>
> 
>