linux-kernel - Re: [PATCH 5/5] i2c: Add Actions Semi OWL family S900 I2C driver

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Message-ID: <CAHp75VdR5UbGvM3AOu21+Hp1xqPgtSnjRSKyhnCeB8ebAmF7eQ@mail.gmail.com>
Date:   Tue, 26 Jun 2018 20:18:44 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     Wolfram Sang <wsa@...-dreams.de>, Rob Herring <robh+dt@...nel.org>,
        Andreas Färber <afaerber@...e.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-i2c <linux-i2c@...r.kernel.org>,
        刘炜 <liuwei@...ions-semi.com>,
        mp-cs@...ions-semi.com, 96boards@...obotics.com,
        devicetree <devicetree@...r.kernel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        amit.kucheria@...aro.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        hzhang@...obotics.com, bdong@...obotics.com,
        Mani Sadhasivam <manivannanece23@...il.com>,
        Thomas Liau <thomas.liau@...ions-semi.com>,
        jeff.chen@...ions-semi.com
Subject: Re: [PATCH 5/5] i2c: Add Actions Semi OWL family S900 I2C driver

On Tue, Jun 26, 2018 at 8:01 PM, Manivannan Sadhasivam
<manivannan.sadhasivam@...aro.org> wrote:
> On Mon, Jun 25, 2018 at 12:38:50PM +0300, Andy Shevchenko wrote:
>> On Sat, Jun 23, 2018 at 7:11 PM, Manivannan Sadhasivam
>> <manivannan.sadhasivam@...aro.org> wrote:

>> > +#define OWL_I2C_REG_CTL                (0x0000)
>> > +#define OWL_I2C_REG_CLKDIV     (0x0004)
>> > +#define OWL_I2C_REG_STAT       (0x0008)
>> > +#define OWL_I2C_REG_ADDR       (0x000C)
>> > +#define OWL_I2C_REG_TXDAT      (0x0010)
>> > +#define OWL_I2C_REG_RXDAT      (0x0014)
>> > +#define OWL_I2C_REG_CMD                (0x0018)
>> > +#define OWL_I2C_REG_FIFOCTL    (0x001C)
>> > +#define OWL_I2C_REG_FIFOSTAT   (0x0020)
>> > +#define OWL_I2C_REG_DATCNT     (0x0024)
>> > +#define OWL_I2C_REG_RCNT       (0x0028)
>>
>> I don't understand why these have parents?
>>
>
> I'm not sure what you mean here! Can you please elaborate?

One has to read 'parens'. Sorry for confusion.

>> > +#define OWL_I2C_TIMEOUT                (msecs_to_jiffies(4 * 1000))
>>
>> Ditto.

> Same as above

Ditto.

>> > +       /* Wait until FIFO reset complete */
>> > +       do {
>> > +               val = readl(i2c_dev->base + OWL_I2C_REG_FIFOCTL);
>> > +               if (!(val & (OWL_I2C_FIFOCTL_RFR | OWL_I2C_FIFOCTL_TFR)))
>> > +                       break;
>> > +       } while (1);
>>
>> No way. Get rid of infinite loop.

> Okay. Can I change it to max of 50 retries with 1ms delay?

Whatever suitable for HW. Rely on datasheet or other source of
information about this timeouts.

>> > +static irqreturn_t owl_i2c_interrupt(int irq, void *_dev)

>> > +               dev_warn(&i2c_dev->adap.dev, "received NACK from device");
>>
>> And if it happens hundreds times in a row?

> Should I change it to dev_dbg?

>> > +               dev_warn(&i2c_dev->adap.dev, "bus error");

> Same as above?

ratelimit, another level, tracepoints, getting rid of them completely
— your call.

-- 
With Best Regards,
Andy Shevchenko