linux-kernel - Re: [PATCH v2] i2c: npcm7xx: Support changing bus speed using debugfs.

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Date:   Wed, 14 Oct 2020 05:30:41 +0000
From:   Joel Stanley <joel@....id.au>
To:     Tali Perry <tali.perry1@...il.com>
Cc:     wsa@...nel.org, andriy.shevchenko@...ux.intel.com, xqiu@...gle.com,
        Kun Yi <kunyi@...gle.com>,
        Benjamin Fair <benjaminfair@...gle.com>,
        Avi Fishman <avifishman70@...il.com>,
        Tomer Maimon <tmaimon77@...il.com>, linux-i2c@...r.kernel.org,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] i2c: npcm7xx: Support changing bus speed using debugfs.

On Tue, 13 Oct 2020 at 10:03, Tali Perry <tali.perry1@...il.com> 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
>
> Fixes: 56a1485b102e (i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver)
> Signed-off-by: Tali Perry <tali.perry1@...il.com>

Reviewed-by: Joel Stanley <joel@....id.au>

I'm not sure that the Fixes tag is quite correct, but it's no biggie.


> ---
>  drivers/i2c/busses/i2c-npcm7xx.c | 35 ++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
>
> 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
>