linux-kernel - Re: [PATCH v3 11/11] i2c: npcm: Support NPCM845

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Date:   Thu, 3 Mar 2022 14:35:58 +0200
From:   Tali Perry <tali.perry1@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Tyrone Ting <warp5tw@...il.com>, avifishman70@...il.com,
        Tomer Maimon <tmaimon77@...il.com>,
        Patrick Venture <venture@...gle.com>,
        Nancy Yuen <yuenn@...gle.com>,
        Benjamin Fair <benjaminfair@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        yangyicong@...ilicon.com, semen.protsenko@...aro.org,
        Wolfram Sang <wsa@...nel.org>, jie.deng@...el.com,
        sven@...npeter.dev, bence98@....bme.hu, lukas.bulwahn@...il.com,
        arnd@...db.de, olof@...om.net, Tali Perry <tali.perry@...oton.com>,
        Avi Fishman <Avi.Fishman@...oton.com>,
        tomer.maimon@...oton.com, KWLIU@...oton.com, JJLIU0@...oton.com,
        kfting@...oton.com, OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Linux I2C <linux-i2c@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 11/11] i2c: npcm: Support NPCM845

> On Thu, Mar 3, 2022 at 12:45 PM Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> >
> > On Thu, Mar 03, 2022 at 04:31:41PM +0800, Tyrone Ting wrote:
> > > From: Tyrone Ting <kfting@...oton.com>
> > >
> > > Add NPCM8XX I2C support.
> > > The NPCM8XX uses a similar i2c module as NPCM7XX.
> > > The internal HW FIFO is larger in NPCM8XX.
> > >
> > > Signed-off-by: Tyrone Ting <kfting@...oton.com>
> > > Signed-off-by: Tali Perry <tali.perry1@...il.com>
> >
> > Wrong SoB chain.
> >
> > ...
> >
> > > +static const struct npcm_i2c_data npxm7xx_i2c_data = {
> > > +     .fifo_size = 16,
> > > +     .segctl_init_val = 0x0333F000,
> > > +     .txf_sts_tx_bytes = GENMASK(4, 0),
> > > +     .rxf_sts_rx_bytes = GENMASK(4, 0),
> > > +     .rxf_ctl_last_pec = BIT(5)
> >
> > + Comma.
> >
> > > +};
> > > +
> > > +static const struct npcm_i2c_data npxm8xx_i2c_data = {
> > > +     .fifo_size = 32,
> > > +     .segctl_init_val = 0x9333F000,
> > > +     .txf_sts_tx_bytes = GENMASK(5, 0),
> > > +     .rxf_sts_rx_bytes = GENMASK(5, 0),
> > > +     .rxf_ctl_last_pec = BIT(7)
> >
> > Ditto.
> >
> > > +};
> >
> > ...
> >
> > > -     left_in_fifo = FIELD_GET(NPCM_I2CTXF_STS_TX_BYTES,
> > > -                              ioread8(bus->reg + NPCM_I2CTXF_STS));
> > > +     left_in_fifo = (bus->data->txf_sts_tx_bytes &
> > > +                     ioread8(bus->reg + NPCM_I2CTXF_STS));
> >
> > Besides too many parentheses, this is an interesting change. So, in different
> > versions of IP the field is on different bits? Perhaps it means that you need
> > something like internal ops structure for all these, where you will have been
> > using the statically defined masks?
> >

Those are two very similar modules. The first generation had a 16 bytes HW FIFO
and the second generation has 32 bytes.
In V1 of this patchset the masks were defined under
CONFIG but we were asked to change the approach:

the entire discussion can be found here:

https://www.spinics.net/lists/linux-i2c/msg55566.html

Did we understand the request change right?


> > ...
> >
> > > +     match = of_match_device(npcm_i2c_bus_of_table, dev);
> > > +     if (!match) {
> > > +             dev_err(dev, "OF data missing\n");
> > > +             return -EINVAL;
> > > +     }
> > > +     bus->data = match->data;
> >
> > This is NIH of_device_get_match_data().
> >
> > ...
> >
> > > -static const struct of_device_id npcm_i2c_bus_of_table[] = {
> > > -     { .compatible = "nuvoton,npcm750-i2c", },
> > > -     {}
> > > -};
> > > -MODULE_DEVICE_TABLE(of, npcm_i2c_bus_of_table);
> > > -
> >
> > Redundant change, leave this as is.
> >
> > --
> > With Best Regards,
> > Andy Shevchenko
> >
> >

Thanks for the detailed review, Andy!

BR,
Tali Perry
Nuvoton Technologies