linux-kernel - Re: [PATCH 2/2] i2c: designware: slave should do WRITE_REQUESTED before WRITE

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Message-ID: <85c6cb3f-2eeb-07c7-0a53-a502b45c91a5@linux.intel.com>
Date:   Fri, 30 Oct 2020 16:46:02 +0200
From:   Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:     Michael Wu <michael.wu@...ics.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Wolfram Sang <wsa@...nel.org>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Morgan Chang <morgan.chang@...ics.com>
Subject: Re: [PATCH 2/2] i2c: designware: slave should do WRITE_REQUESTED
 before WRITE_RECEIVED

On 10/30/20 10:04 AM, Michael Wu wrote:
> Sometimes we would get the following flow when doing an i2cset:
> 
> 0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
> I2C_SLAVE_WRITE_RECEIVED
> 0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x714 : INTR_STAT=0x204
> I2C_SLAVE_WRITE_REQUESTED
> I2C_SLAVE_WRITE_RECEIVED
> 
> Documentation/i2c/slave-interface.rst says that I2C_SLAVE_WRITE_REQUESTED,
> which is mandatory, should be sent while the data did not arrive yet. It
> means in a write-request I2C_SLAVE_WRITE_REQUESTED should be reported
> before any I2C_SLAVE_WRITE_RECEIVED.
> 
> By the way, I2C_SLAVE_STOP didn't be reported in the above case because
> DW_IC_INTR_STAT was not 0x200.
> 
> dev->status can be used to record the current state, especially Designware
> I2C controller has no interrupts to identify a write-request. This patch
> makes not only I2C_SLAVE_WRITE_REQUESTED been reported first when
> IC_INTR_RX_FULL is rising and dev->status isn't STATUS_WRITE_IN_PROGRESS
> but also I2C_SLAVE_STOP been reported when a STOP condition is received.
> 
> Signed-off-by: Michael Wu <michael.wu@...ics.com>
> ---
>   drivers/i2c/busses/i2c-designware-slave.c | 45 +++++++++--------------
>   1 file changed, 18 insertions(+), 27 deletions(-)
> 
Acked-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>