linux-kernel - Re: [PATCH v8 8/8] i2c: rk3x: support fast-mode plus for rk3399

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Message-ID: <5153288.jNhUuzGC3g@phil>
Date:	Wed, 11 May 2016 23:09:43 +0200
From:	Heiko Stuebner <heiko@...ech.de>
To:	David Wu <david.wu@...k-chips.com>
Cc:	wsa@...-dreams.de, robh+dt@...nel.org, dianders@...omium.org,
	andy.shevchenko@...il.com, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, briannorris@...gle.com,
	davidriley@...gle.com, huangtao@...k-chips.com, hl@...k-chips.com,
	xjq@...k-chips.com, zyw@...k-chips.com, cf@...k-chips.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, linux-i2c@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 8/8] i2c: rk3x: support fast-mode plus for rk3399

Am Mittwoch, 11. Mai 2016, 03:33:14 schrieb David Wu:

please always try to also provide some sort of commit message.

---
Implement fast mode plus that allows bus speeds of up to 1MHz.
.....

---

Additionally, the i2c-noob in me would wish for a short sentence on where 
the timing values come from (measured, somewhere in the TRM I didn't find or 
something completely different).


Patch content itself looks good, so with a suitable commit message,
Reviewed-by: Heiko Stuebner <heiko@...ech.de>


> Signed-off-by: David Wu <david.wu@...k-chips.com>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
> ---
> Change in v8:
> - None
> 
>  drivers/i2c/busses/i2c-rk3x.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-rk3x.c b/drivers/i2c/busses/i2c-rk3x.c
> index 25ed1ad..0ba25ee 100644
> --- a/drivers/i2c/busses/i2c-rk3x.c
> +++ b/drivers/i2c/busses/i2c-rk3x.c
> @@ -126,6 +126,17 @@ static const struct i2c_spec_values fast_mode_spec =
> { .min_hold_buffer_ns = 1300,
>  };
> 
> +static const struct i2c_spec_values fast_mode_plus_spec = {
> +	.min_hold_start_ns = 260,
> +	.min_low_ns = 500,
> +	.min_high_ns = 260,
> +	.min_setup_start_ns = 260,
> +	.max_data_hold_ns = 400,
> +	.min_data_setup_ns = 50,
> +	.min_setup_stop_ns = 260,
> +	.min_hold_buffer_ns = 500,
> +};
> +
>  /**
>   * struct rk3x_i2c_calced_timings:
>   * @div_low: Divider output for low
> @@ -531,8 +542,10 @@ static const struct i2c_spec_values
> *rk3x_i2c_get_spec(unsigned int speed) {
>  	if (speed <= 100000)
>  		return &standard_mode_spec;
> -	else
> +	else if (speed <= 400000)
>  		return &fast_mode_spec;
> +	else
> +		return &fast_mode_plus_spec;
>  }
> 
>  /**
> @@ -743,9 +756,9 @@ static int rk3x_i2c_v1_calc_timings(unsigned long
> clk_rate, const struct i2c_spec_values *spec;
>  	int ret = 0;
> 
> -	/* Support standard-mode and fast-mode */
> -	if (WARN_ON(t->bus_freq_hz > 400000))
> -		t->bus_freq_hz = 400000;
> +	/* Support standard-mode, fast-mode and fast-mode plus */
> +	if (WARN_ON(t->bus_freq_hz > 1000000))
> +		t->bus_freq_hz = 1000000;
> 
>  	/* prevent scl_rate_khz from becoming 0 */
>  	if (WARN_ON(t->bus_freq_hz < 1000))