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

Andrew Jeffery
2023-12-08T03:56:45Z

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@os.amperecomputing.com>
> ---
> 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@os.amperecomputing.com/
> ---
> 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@codeconstruct.com.au>

> + * Now that we've dealt with any potentially coalesced stop conditions,
> + * address any start conditions.
> + */
> if (irq_status & ASPEED_I2CD_INTR_SLAVE_MATCH) {
> irq_handled |= ASPEED_I2CD_INTR_SLAVE_MATCH;
> bus->slave_state = ASPEED_I2C_SLAVE_START;
> }
>