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From:   Alex Qiu <xqiu@google.com>
Date:   Tue, 13 Oct 2020 14:29:11 -0700
Message-ID: <CAA_a9xKSYjjX47AT_XduA7WyrM5nCNu4vJLUsjwBEAyy7jn0BQ@mail.gmail.com>
Subject: Re: [PATCH v2] i2c: npcm7xx: Support changing bus speed using debugfs.
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     Tali Perry <tali.perry1@gmail.com>, Wolfram Sang <wsa@kernel.org>,
        Kun Yi <kunyi@google.com>,
        Benjamin Fair <benjaminfair@google.com>,
        Avi Fishman <avifishman70@gmail.com>,
        Joel Stanley <joel@jms.id.au>,
        Tomer Maimon <tmaimon77@gmail.com>,
        Linux I2C <linux-i2c@vger.kernel.org>,
        OpenBMC Maillist <openbmc@lists.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Tested again, and the updated patch is still working.

On Tue, Oct 13, 2020 at 4:49 AM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Tue, Oct 13, 2020 at 01:03:14PM +0300, Tali Perry wrote:
> > Systems that can dynamically add and remove slave devices
> > often need to change the bus speed in runtime.
> > This patch expose the bus frequency to the user.
> > This feature can also be used for test automation.
>
> > --
> > v2 -> v1:
> >       - Fix typos.
> >       - Remove casting to u64.
> >
> > v1: initial version
>
> Above block should go after cutter '---' (see below) line...
>
> > Fixes: 56a1485b102e (i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver)
> > Signed-off-by: Tali Perry <tali.perry1@gmail.com>
Reviewed-by: Alex Qiu <xqiu@google.com>
Tested-by: Alex Qiu <xqiu@google.com>

> > ---
>
> ...here.
>
> >  drivers/i2c/busses/i2c-npcm7xx.c | 35 ++++++++++++++++++++++++++++++++
> >  1 file changed, 35 insertions(+)
>
> As we discussed previously I'm not a fan of the functionality this gives and a
> way it's done, but this is debugfs and not anyhow an ABI. Also it's localized
> inside one driver. In the future we may come up with better approach.
>
> That said, no objections from me.
>
> > diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
> > index 2ad166355ec9..633ac67153e2 100644
> > --- a/drivers/i2c/busses/i2c-npcm7xx.c
> > +++ b/drivers/i2c/busses/i2c-npcm7xx.c
> > @@ -2208,6 +2208,40 @@ static const struct i2c_algorithm npcm_i2c_algo = {
> >  /* i2c debugfs directory: used to keep health monitor of i2c devices */
> >  static struct dentry *npcm_i2c_debugfs_dir;
> >
> > +static int i2c_speed_get(void *data, u64 *val)
> > +{
> > +     struct npcm_i2c *bus = data;
> > +
> > +     *val = bus->bus_freq;
> > +     return 0;
> > +}
> > +
> > +static int i2c_speed_set(void *data, u64 val)
> > +{
> > +     struct npcm_i2c *bus = data;
> > +     int ret;
> > +
> > +     if (val < I2C_FREQ_MIN_HZ || val > I2C_FREQ_MAX_HZ)
> > +             return -EINVAL;
> > +
> > +     if (val == bus->bus_freq)
> > +             return 0;
> > +
> > +     i2c_lock_bus(&bus->adap, I2C_LOCK_ROOT_ADAPTER);
> > +
> > +     npcm_i2c_int_enable(bus, false);
> > +
> > +     ret = npcm_i2c_init_module(bus, I2C_MASTER, (u32)val);
> > +
> > +     i2c_unlock_bus(&bus->adap, I2C_LOCK_ROOT_ADAPTER);
> > +
> > +     if (ret)
> > +             return -EAGAIN;
> > +
> > +     return 0;
> > +}
> > +DEFINE_DEBUGFS_ATTRIBUTE(i2c_clock_ops, i2c_speed_get, i2c_speed_set, "%llu\n");
> > +
> >  static void npcm_i2c_init_debugfs(struct platform_device *pdev,
> >                                 struct npcm_i2c *bus)
> >  {
> > @@ -2223,6 +2257,7 @@ static void npcm_i2c_init_debugfs(struct platform_device *pdev,
> >       debugfs_create_u64("rec_succ_cnt", 0444, d, &bus->rec_succ_cnt);
> >       debugfs_create_u64("rec_fail_cnt", 0444, d, &bus->rec_fail_cnt);
> >       debugfs_create_u64("timeout_cnt", 0444, d, &bus->timeout_cnt);
> > +     debugfs_create_file("i2c_speed", 0644, d, bus, &i2c_clock_ops);
> >
> >       bus->debugfs = d;
> >  }
> >
> > base-commit: 865c50e1d279671728c2936cb7680eb89355eeea
> > --
> > 2.22.0
> >
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

- Alex Qiu