linux-kernel - Re: [PATCH] i2c: designware-platdrv: get fast/std speed scl high/low count from DT

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Date:	Wed, 13 Apr 2016 20:16:37 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
CC:	Wolfram Sang <wsa@...-dreams.de>, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	ijc+devicetree <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	"Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	<linux-i2c@...r.kernel.org>,
	devicetree <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] i2c: designware-platdrv: get fast/std speed scl
 high/low count from DT

Dear Andy,

On Thu, 7 Apr 2016 21:05:35 +0300 Andy Shevchenko  wrote:

> On Wed, Apr 6, 2016 at 10:28 AM, Jisheng Zhang <jszhang@...vell.com> wrote:
> > Sometimes, it's convenient to define the scl's high/low count directly,
> > e.g HW people would do some measurement then directly give out the
> > optimum counts. Previously, we solved the sda falling time and scl
> > falling time by i2c_dw_scl_hcnt() and i2c_dw_scl_lcnt(), then put them
> > into dt, but what we really care isn't the sda/scl falling time.
> >
> > From another side, the dw_i2c_acpi_configure() on ACPI platform also
> > get hcnt/lcnt values rather than the sda/scl falling time from ACPI
> > method, we want similar feature for DT platforms.
> >  
> 
> Instead of duplicating some words maybe better to explicitly define
> two groups of parameters and one which supersedes the other.

I'm sorry, I can't catch your meaning. Could you please kindly give more
details? Or examples of "two groups of parameters"

Thanks,
Jisheng

> 
> > Signed-off-by: Jisheng Zhang <jszhang@...vell.com>
> > ---
> >  Documentation/devicetree/bindings/i2c/i2c-designware.txt | 16 ++++++++++++++++
> >  drivers/i2c/busses/i2c-designware-platdrv.c              |  8 ++++++++
> >  2 files changed, 24 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> > index fee26dc..05176fbf 100644
> > --- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> > +++ b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> > @@ -20,6 +20,22 @@ Optional properties :
> >   - i2c-sda-falling-time-ns : should contain the SDA falling time in nanoseconds.
> >     This value which is by default 300ns is used to compute the tHIGH period.
> >
> > + - i2c-ss-scl-high-count : should contain the standard speed i2c clock SCL high
> > +   count. If defined, the i2c-scl-falling-time-ns and i2c-sda-falling-time-ns
> > +   will be ignored.
> > +
> > + - i2c-ss-scl-low-count : should contain the standard speed i2c clock SCL low
> > +   count. If defined, the i2c-scl-falling-time-ns and i2c-sda-falling-time-ns
> > +   will be ignored.
> > +
> > + - i2c-fs-scl-high-count : should contain the fast speed i2c clock SCL high
> > +   count. If defined, the i2c-scl-falling-time-ns and i2c-sda-falling-time-ns
> > +   will be ignored.
> > +
> > + - i2c-fs-scl-low-count : should contain the fast speed i2c clock SCL low
> > +   count. If defined, the i2c-scl-falling-time-ns and i2c-sda-falling-time-ns
> > +   will be ignored.
> > +
> >  Example :
> >
> >         i2c@...00 {
> > diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> > index d656657..8739a60 100644
> > --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> > +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> > @@ -188,6 +188,14 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
> >                                          &dev->scl_falling_time);
> >                 device_property_read_u32(&pdev->dev, "clock-frequency",
> >                                          &clk_freq);
> > +               device_property_read_u16(&pdev->dev, "i2c-ss-scl-high-count",
> > +                                        &dev->ss_hcnt);
> > +               device_property_read_u16(&pdev->dev, "i2c-ss-scl-low-count",
> > +                                        &dev->ss_lcnt);
> > +               device_property_read_u16(&pdev->dev, "i2c-fs-scl-high-count",
> > +                                        &dev->fs_hcnt);
> > +               device_property_read_u16(&pdev->dev, "i2c-fs-scl-low-count",
> > +                                        &dev->fs_lcnt);
> >         }
> >
> >         if (has_acpi_companion(&pdev->dev))
> > --
> > 2.8.0.rc3
> >  
> 
> 
>