linux-kernel - Re: [PATCH i2c-next v6] i2c: aspeed: Handle master/slave combined irq events properly

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Message-ID: <20180913155703.GA22605@roeck-us.net>
Date:   Thu, 13 Sep 2018 08:57:03 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Cédric Le Goater <clg@...d.org>
Cc:     Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>,
        Joel Stanley <joel@....id.au>, linux-aspeed@...ts.ozlabs.org,
        Vernon Mauery <vernon.mauery@...ux.intel.com>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-i2c@...r.kernel.org, jarkko.nikula@...ux.intel.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        James Feist <james.feist@...ux.intel.com>
Subject: Re: [PATCH i2c-next v6] i2c: aspeed: Handle master/slave combined
 irq events properly

On Thu, Sep 13, 2018 at 05:48:59PM +0200, Cédric Le Goater wrote:
> On 09/13/2018 03:33 PM, Guenter Roeck wrote:
[ ... ]
> >>>   /*
> >>>    * The state machine needs some refinement. It is only used to track
> >>>    * invalid STOP commands for the moment.
> >>> @@ -188,7 +215,7 @@ static void aspeed_i2c_bus_handle_cmd(AspeedI2CBus *bus, uint64_t value)
> >>>   {
> >>>       bus->cmd &= ~0xFFFF;
> >>>       bus->cmd |= value & 0xFFFF;
> >>> -    bus->intr_status = 0;> +    bus->intr_status &= I2CD_INTR_RX_DONE;
> >>
> >> it deserves a comment to understand which scenario we are trying to handle.
> >>    
> > 
> > Ok. FWIW, I wonder if intr_status should be touched here in the first place,
> > but I neither have the hardware nor a datasheet, so I don't know if any bits
> > are auto-cleared.
> 
> I just pushed a patch on my branch with some more explanation : 
> 
> 	https://github.com/legoater/qemu/commits/aspeed-3.1
> 
That seems to suggest that none of the status bits auto-clears, and that
the above code clearing intr_status should be removed entirely.
Am I missing something ?

Thanks,
Guenter