linux-kernel - Re: [PATCH v10 2/3] i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver

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Message-ID: <20200513152413.GQ185537@smile.fi.intel.com>
Date:   Wed, 13 May 2020 18:24:13 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Tali Perry <tali.perry1@...il.com>
Cc:     ofery@...gle.com, Brendan Higgins <brendanhiggins@...gle.com>,
        avifishman70@...il.com, Tomer Maimon <tmaimon77@...il.com>,
        kfting@...oton.com, Patrick Venture <venture@...gle.com>,
        Nancy Yuen <yuenn@...gle.com>,
        Benjamin Fair <benjaminfair@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        linux-arm-kernel@...ts.infradead.org, linux-i2c@...r.kernel.org,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 2/3] i2c: npcm7xx: Add Nuvoton NPCM I2C controller
 driver

On Mon, May 11, 2020 at 02:28:50PM +0300, Tali Perry wrote:
> On Mon, May 11, 2020 at 12:18 PM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> > On Sun, May 10, 2020 at 01:23:29PM +0300, Tali Perry wrote:

...

> > > +#if IS_ENABLED(CONFIG_DEBUG_FS)
> >
> > Why?
> 
> We wanted to add an optional feature to track i2c slave status.
> the NPCM has 16 channels handling multiple devices each. Some of the devices
> are polled periodically, and might power down.
> The user wanted to implement a health monitoring option
> to occasionally check the status of the buses (how many timeouts, recovery etc.)
> This feature is optional and depends on CONFIG_DEBUG_FS The counters are exposed
> to user through the file system.

What I meant is why do you need an #ifdef?


...

> > > +#define I2C_NUM_OF_ADDR 10
> >
> > Is it 10-bit address support or what?
> >
> 
> No, the NPCM has an option to respond to multiple slave addresses
> (10 own slave addresses)

Perhaps more descriptive name then?

...

> > > +     // Repeat the following sequence until SDA is released
> > > +     do {
> > > +             // Issue a single SCL toggle
> > > +             iowrite8(NPCM_I2CCST_TGSCL, bus->reg + NPCM_I2CCST);
> > > +             udelay(20);
> > > +             // If SDA line is inactive (high), stop
> > > +             if (npcm_i2c_get_SDA(_adap)) {
> > > +                     done = true;
> > > +                     status = 0;
> > > +             }
> > > +     } while (!done && iter--);
> >
> > readx_poll_timeout() ?
> 
> Not exactly, readx_poll_timeout includes only a read operation, here there is a
> write in the middle. (iowrite8)

Ah, indeed. Perhaps time to add writex_poll_timeout() ?

-- 
With Best Regards,
Andy Shevchenko