Re: [PATCH v3 1/2] i2c: aspeed: Handle the coalesced stop conditions with the start conditions.

[Quan Nguyen]

On 08/12/2023 10:56, Andrew Jeffery wrote:
> On Fri, 2023-12-08 at 10:31 +0700, Quan Nguyen wrote:
> > Some masters may drive the transfers with low enough latency between
> > the nak/stop phase of the current command and the start/address phase
> > of the following command that the interrupts are coalesced by the
> > time we process them.
> > Handle the stop conditions before processing SLAVE_MATCH to fix the
> > complaints that sometimes occur below.
> >
> > "aspeed-i2c-bus 1e78a040.i2c-bus: irq handled != irq. Expected
> > 0x00000086, but was 0x00000084"
> >
> > Fixes: f9eb91350bb2 ("i2c: aspeed: added slave support for Aspeed I2C driver")
> > Signed-off-by: Quan Nguyen <quan@xxxxxxxxxxxxxxxxxxxxxx>
> > ---
> > v3:
> >    + Change to handle the coalesced stop condition with the start
> > conditions                                                            [Andrew]
> >    + Revised commit message                                              [Quan]
> >
> > v2:
> >    + Split to separate series                                            [Joel]
> >    + Added the Fixes line                                                [Joel]
> >    + Revised commit message                                              [Quan]
> >
> > v1:
> >    + First introduced in
> > https://lore.kernel.org/all/20210519074934.20712-1-quan@xxxxxxxxxxxxxxxxxxxxxx/
> > ---
> >   drivers/i2c/busses/i2c-aspeed.c | 47 ++++++++++++++++++++++-----------
> >   1 file changed, 31 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> > index 28e2a5fc4528..1c2a4f4c4e1b 100644
> > --- a/drivers/i2c/busses/i2c-aspeed.c
> > +++ b/drivers/i2c/busses/i2c-aspeed.c
> > @@ -249,18 +249,45 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
> >   	if (!slave)
> >   		return 0;
> >   
> > -	command = readl(bus->base + ASPEED_I2C_CMD_REG);
> > +	/*
> > +	 * Handle stop conditions early, prior to SLAVE_MATCH. Some masters may drive
> > +	 * transfers with low enough latency between the nak/stop phase of the current
> > +	 * command and the start/address phase of the following command that the
> > +	 * interrupts are coalesced by the time we process them.
> > +	 */
> > +	if (irq_status & ASPEED_I2CD_INTR_NORMAL_STOP) {
> > +		irq_handled |= ASPEED_I2CD_INTR_NORMAL_STOP;
> > +		bus->slave_state = ASPEED_I2C_SLAVE_STOP;
> > +	}
> >   
> > -	/* Slave was requested, restart state machine. */
> > +	if (irq_status & ASPEED_I2CD_INTR_TX_NAK &&
> > +	    bus->slave_state == ASPEED_I2C_SLAVE_READ_PROCESSED) {
> > +		irq_handled |= ASPEED_I2CD_INTR_TX_NAK;
> > +		bus->slave_state = ASPEED_I2C_SLAVE_STOP;
> > +	}
> > +
> > +	/* Propagate any stop conditions to the slave implementation. */
> > +	if (bus->slave_state == ASPEED_I2C_SLAVE_STOP) {
> > +		i2c_slave_event(slave, I2C_SLAVE_STOP, &value);
> > +		bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
> > +	}
> > +	/*
>
> If there's a reason to do a v4 then an extra empty line above the
> comment would be nice. But let's not get hung up on that if everyone
> else is happy.
>
> Thanks for the fixes!
>
> Reviewed-by: Andrew Jeffery <andrew@xxxxxxxxxxxxxxxxxxxx>

Thanks Andrew,

I'll add your Reviewed-by in my v4 with that extra empty lime before the 
comment.

Thanks for the review
- Quan