Re: [PATCH v3 2/2] i2c: aspeed: Acknowledge Tx done with and without ACK irq late

Andrew Jeffery
2023-12-08T04:00:21Z

On Fri, 2023-12-08 at 10:31 +0700, Quan Nguyen wrote:
> Commit 2be6b47211e1 ("i2c: aspeed: Acknowledge most interrupts early in
> interrupt handler") acknowledges most interrupts early before the slave
> irq handler is executed, except for the "Receive Done Interrupt status"
> which is acknowledged late in the interrupt.
> However, it has been observed that the early acknowledgment of "Transmit
> Done Interrupt Status" (with ACK or NACK) often causes the interrupt to
> be raised in READ REQUEST state, that shows the
> "Unexpected ACK on read request." complaint messages.
>
> Assuming that the "Transmit Done" interrupt should only be acknowledged
> once it is truly processed, this commit fixes that issue by acknowledging
> interrupts for both ACK and NACK cases late in the interrupt handler.
>
> Fixes: 2be6b47211e1 ("i2c: aspeed: Acknowledge most interrupts early in interrupt handler")
> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
> ---
> v3:
> + Fix the unconditinal write when ack the irqs [Andrew]
> + Refactor the code to enhance code readability [Quan]
> + Fix grammar in commit message [Quan]
>
> v2:
> + Split to separate series [Joel]
> + Added the Fixes line [Joel]
> + Fixed multiline comment [Joel]
> + Refactor irq clearing code [Joel, Guenter]
> + Revised commit message [Joel]
> + Revised commit message [Quan]
> + About a note to remind why the readl() should immediately follow the
> writel() to fix the race condition when clearing irq status from commit
> c926c87b8e36 ("i2c: aspeed: Avoid i2c interrupt status clear race
> condition"), I think it looks straight forward in this patch and decided
> not to add that note. [Joel]
>
> v1:
> + First introduced in
> https://lore.kernel.org/all/20210519074934.20712-1-quan@os.amperecomputing.com/
> ---
> drivers/i2c/busses/i2c-aspeed.c | 21 +++++++++++++--------
> 1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index 1c2a4f4c4e1b..967a26dd4ffa 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -617,13 +617,19 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
> static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
> {
> struct aspeed_i2c_bus *bus = dev_id;
> - u32 irq_received, irq_remaining, irq_handled;
> + u32 irq_received, irq_remaining, irq_handled, irq_ack_last;

`irq_ack_last` might be better as a macro, but you're probably saved by
the optimiser anyway. If there's another reason to do a v4 or others
are unhappy with it then consider fixing it, otherwise:

Reviewed-by: Andrew Jeffery <andrew@codeconstruct.com.au>

Thanks.