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Date:   Tue, 25 Aug 2020 13:05:24 -0700
From:   Tao Ren <rentao.bupt@gmail.com>
To:     Eddie James <eajames@linux.ibm.com>
Cc:     Joel Stanley <joel@jms.id.au>,
        devicetree <devicetree@vger.kernel.org>,
        linux-aspeed <linux-aspeed@lists.ozlabs.org>,
        dmitry.torokhov@gmail.com,
        Brendan Higgins <brendanhiggins@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Rob Herring <robh+dt@kernel.org>, linux-i2c@vger.kernel.org,
        linux-input@vger.kernel.org, ryan_chen@aspeedtech.com
Subject: Re: [PATCH 3/5] i2c: aspeed: Mask IRQ status to relevant bits
Message-ID: <20200825200523.GA22083@taoren-ubuntu-R90MNF91>
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On Tue, Aug 25, 2020 at 02:47:51PM -0500, Eddie James wrote:
> 
> On 8/25/20 1:38 AM, Joel Stanley wrote:
> > On Thu, 20 Aug 2020 at 16:12, Eddie James <eajames@linux.ibm.com> wrote:
> > > Mask the IRQ status to only the bits that the driver checks. This
> > > prevents excessive driver warnings when operating in slave mode
> > > when additional bits are set that the driver doesn't handle.
> > > 
> > > Signed-off-by: Eddie James <eajames@linux.ibm.com>
> > > ---
> > >   drivers/i2c/busses/i2c-aspeed.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> > > index 31268074c422..abf40f2af8b4 100644
> > > --- a/drivers/i2c/busses/i2c-aspeed.c
> > > +++ b/drivers/i2c/busses/i2c-aspeed.c
> > > @@ -604,6 +604,7 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
> > >          writel(irq_received & ~ASPEED_I2CD_INTR_RX_DONE,
> > >                 bus->base + ASPEED_I2C_INTR_STS_REG);
> > >          readl(bus->base + ASPEED_I2C_INTR_STS_REG);
> > > +       irq_received &= 0xf000ffff;
> > >          irq_remaining = irq_received;
> > This would defeat the check for irq_remaining. I don't think we want to do this.
> > 
> > Can you explain why these bits are being set in slave mode?
> 
> 
> No, I don't have any documentation for the bits that are masked off here, so
> I don't know why they would get set.
> 
> The check for irq_remaining is still useful for detecting that the driver
> state machine might be out of sync with what the master is doing.

I have a similar patch in my local tree, and the reason being: AST2600
I2C Controller may set I2CD10[25:24] to report Current Slave Parking
Status (defined in new register I2CS24) even though the new register
mode is off. The 2 bits can be ignored in legacy mode, and Ryan from
ASPEED could confirm it.


Cheers,

Tao