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Message-ID: <79ce9162faeb113ecb13efeb58d95f8a71e1a060.camel@codeconstruct.com.au>
Subject: Re: [PATCH v3 1/2] i2c: aspeed: Handle the coalesced stop
 conditions with the start conditions.
From:   Andrew Jeffery <andrew@codeconstruct.com.au>
To:     Quan Nguyen <quan@os.amperecomputing.com>,
        Brendan Higgins <brendan.higgins@linux.dev>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Joel Stanley <joel@jms.id.au>,
        Andi Shyti <andi.shyti@kernel.org>,
        Wolfram Sang <wsa@kernel.org>,
        Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>,
        Guenter Roeck <linux@roeck-us.net>, linux-i2c@vger.kernel.org,
        openbmc@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org,
        linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org
Cc:     Cosmo Chou <chou.cosmo@gmail.com>,
        Open Source Submission <patches@amperecomputing.com>,
        Phong Vo <phong@os.amperecomputing.com>,
        "Thang Q . Nguyen" <thang@os.amperecomputing.com>
Date:   Fri, 08 Dec 2023 14:26:31 +1030
In-Reply-To: <20231208033142.1673232-2-quan@os.amperecomputing.com>
References: <20231208033142.1673232-1-quan@os.amperecomputing.com>
         <20231208033142.1673232-2-quan@os.amperecomputing.com>
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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.
>=20
> "aspeed-i2c-bus 1e78a040.i2c-bus: irq handled !=3D irq. Expected
> 0x00000086, but was 0x00000084"
>=20
> Fixes: f9eb91350bb2 ("i2c: aspeed: added slave support for Aspeed I2C dri=
ver")
> Signed-off-by: Quan Nguyen <quan@os.amperecomputing.com>
> ---
> v3:
>   + Change to handle the coalesced stop condition with the start
> conditions                                                            [An=
drew]
>   + Revised commit message                                              [=
Quan]
>=20
> v2:
>   + Split to separate series                                            [=
Joel]
>   + Added the Fixes line                                                [=
Joel]
>   + Revised commit message                                              [=
Quan]
>=20
> v1:
>   + First introduced in
> https://lore.kernel.org/all/20210519074934.20712-1-quan@os.amperecomputin=
g.com/
> ---
>  drivers/i2c/busses/i2c-aspeed.c | 47 ++++++++++++++++++++++-----------
>  1 file changed, 31 insertions(+), 16 deletions(-)
>=20
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-asp=
eed.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_b=
us *bus, u32 irq_status)
>  	if (!slave)
>  		return 0;
> =20
> -	command =3D 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 th=
e
> +	 * interrupts are coalesced by the time we process them.
> +	 */
> +	if (irq_status & ASPEED_I2CD_INTR_NORMAL_STOP) {
> +		irq_handled |=3D ASPEED_I2CD_INTR_NORMAL_STOP;
> +		bus->slave_state =3D ASPEED_I2C_SLAVE_STOP;
> +	}
> =20
> -	/* Slave was requested, restart state machine. */
> +	if (irq_status & ASPEED_I2CD_INTR_TX_NAK &&
> +	    bus->slave_state =3D=3D ASPEED_I2C_SLAVE_READ_PROCESSED) {
> +		irq_handled |=3D ASPEED_I2CD_INTR_TX_NAK;
> +		bus->slave_state =3D ASPEED_I2C_SLAVE_STOP;
> +	}
> +
> +	/* Propagate any stop conditions to the slave implementation. */
> +	if (bus->slave_state =3D=3D ASPEED_I2C_SLAVE_STOP) {
> +		i2c_slave_event(slave, I2C_SLAVE_STOP, &value);
> +		bus->slave_state =3D 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 |=3D ASPEED_I2CD_INTR_SLAVE_MATCH;
>  		bus->slave_state =3D ASPEED_I2C_SLAVE_START;
>  	}
> =20