Date: Sun, 24 Apr 2016 22:39:23 +0200
From: Wolfram Sang <wsa@the-dreams.de>
To: Jisheng Zhang <jszhang@marvell.com>
Cc: Rob Herring <robh@kernel.org>, pawel.moll@arm.com, mark.rutland@arm.com,
        ijc+devicetree@hellion.org.uk, galak@codeaurora.org,
        jarkko.nikula@linux.intel.com, andriy.shevchenko@linux.intel.com,
        mika.westerberg@linux.intel.com, linux-i2c@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] i2c: designware-platdrv: get fast/std speed scl high/low
 count from DT
Message-ID: <20160424203922.GC4317@katana>
References: <1459927680-5480-1-git-send-email-jszhang@marvell.com>
 <20160407175759.GO32257@rob-hp-laptop>
 <20160413201147.5621a17c@xhacker>
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On Wed, Apr 13, 2016 at 08:11:47PM +0800, Jisheng Zhang wrote:
> Dear Rob,
>=20
> On Thu, 7 Apr 2016 12:57:59 -0500 Rob Herring wrote:
>=20
> > On Wed, Apr 06, 2016 at 03:28:00PM +0800, Jisheng Zhang wrote:
> > > Sometimes, it's convenient to define the scl's high/low count directl=
y,
> > > 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. =20
> >=20
> > This is just so you can put specific clock count instead of converting=
=20
> > from nanoseconds with standard properties or you gain some additional=
=20
> > control of the timing. If only the former, then I prefer we stick with=
=20
> > the common properties.
>=20
> To be honest, both. Let me show how I gain additional control of the timi=
ng
> with this patch while I can't do this w/o it.
>=20
> I want the similar high percent of SCL high for both standard-mode and
> fast-mode. Before this patch, this is not achievable because the paramete=
rs
> to cal the hcnt/lcnt via i2c_dw_scl_hcnt() and i2c_dw_scl_lcnt() are diff=
erent
> for standard-mode and fast-mode.

If there is something you can't describe currently, then we can add
additional properties to allow you to do what you want. But they should
be generic bindings and not a plain value which is custom to this driver.


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