linux-kernel - Re: [PATCH 2/5] i2c: designware: allow IP specific sda_hold

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Date:   Tue, 17 Jul 2018 17:33:37 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Wolfram Sang <wsa@...-dreams.de>,
        Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        James Hogan <jhogan@...nel.org>
Cc:     Paul Burton <paul.burton@...s.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Allan Nielsen <allan.nielsen@...rosemi.com>
Subject: Re: [PATCH 2/5] i2c: designware: allow IP specific sda_hold_time

On Tue, 2018-07-17 at 13:48 +0200, Alexandre Belloni wrote:
> Because some old designware IPs were not supporting setting an SDA
> hold
> time, vendors developed their own solution. Add a way for the final
> driver
> to provide its own SDA hold time handling.
> 

Thanks for information you provided. See my comment below.
After addressing it, 

Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
> ---
>  drivers/i2c/busses/i2c-designware-common.c | 6 ++++++
>  drivers/i2c/busses/i2c-designware-core.h   | 1 +
>  2 files changed, 7 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-designware-common.c
> b/drivers/i2c/busses/i2c-designware-common.c
> index 9afc3e075b33..545b69d6be3c 100644
> --- a/drivers/i2c/busses/i2c-designware-common.c
> +++ b/drivers/i2c/busses/i2c-designware-common.c
> @@ -297,6 +297,12 @@ void i2c_dw_set_sda_hold_time(struct dw_i2c_dev
> *dev)
>  {
>  	u32 reg;
> 

>  
> +	if (dev->set_sda_hold_time) {
> +		dev->set_sda_hold_time(dev);
> +
> +		return;
> +	}

I would rather inject this, for now (*), into if-else-if ladder, i.e.

if (reg >= DW_IC_SDA_HOLD_MIN_VERS) {
 ...
} else if (dev->set_sda_hold_time) { // <<<
 ...
} else if (dev->sda_hold_time) {
 ...

(*) Since your IP is of v1.10a I don't believe any new version of IP
would shadow existing DW IP registers, thus version check is okay to
have first in my opinion.

> +
>  	/* Configure SDA Hold Time if required. */
>  	reg = dw_readl(dev, DW_IC_COMP_VERSION);
>  	if (reg >= DW_IC_SDA_HOLD_MIN_VERS) {
> diff --git a/drivers/i2c/busses/i2c-designware-core.h
> b/drivers/i2c/busses/i2c-designware-core.h
> index bc43fb9ac1cf..b2778b6d8aca 100644
> --- a/drivers/i2c/busses/i2c-designware-core.h
> +++ b/drivers/i2c/busses/i2c-designware-core.h
> @@ -283,6 +283,7 @@ struct dw_i2c_dev {
>  	void			(*disable)(struct dw_i2c_dev
> *dev);
>  	void			(*disable_int)(struct dw_i2c_dev
> *dev);
>  	int			(*init)(struct dw_i2c_dev *dev);
> +	int			(*set_sda_hold_time)(struct
> dw_i2c_dev *dev);
>  	int			mode;
>  	struct i2c_bus_recovery_info rinfo;
>  };

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy