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Message-ID: <alpine.DEB.2.02.1408201008400.11079@atx-linux-37>
Date: Wed, 20 Aug 2014 10:12:14 -0500
From: atull <atull@...nsource.altera.com>
To: Romain Baeriswyl <Romain.Baeriswyl@...lis.com>
CC: Mark Rutland <mark.rutland@....com>, <wsa@...-dreams.de>,
<baruch@...s.co.il>,
mika westerberg <mika.westerberg@...ux.intel.com>,
grant likely <grant.likely@...aro.org>, <robh+dt@...nel.org>,
<skuribay@...ox.com>,
rafael j wysocki <rafael.j.wysocki@...el.com>,
<alan@...ux.intel.com>, <linux-i2c@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
delicious quinoa <delicious.quinoa@...il.com>,
<dinguyen@...nsource.altera.com>, <yvanderv@...nsource.altera.com>
Subject: Re: [PATCH] i2c: designware: deduce speed mode from device tree
setting
On Wed, 20 Aug 2014, Romain Baeriswyl wrote:
> Hi Alan,
>
> We got board issue using I2C and they were solved by changing the i2c timing.
>
> It is possible to change the tLOW and tHIGH period with the following parameters:
> i2c-sda-hold-time-ns
> i2c-sda-falling-time-ns
> i2c-scl-falling-time-ns
>
> Romain
Hi Romain,
This thread is getting kind of messed up. Yep, that's how I am slowing
down the bus, using i2c-sda-falling-time-ns and i2c-scl-falling-time-ns.
It is fine with me if you want to test for == 100KHz, just not my
(probably hair-splitting) preference. :)
Alan
>
> ----- Original Message -----
> From: "atull" <atull@...nsource.altera.com>
> To: "Romain Baeriswyl" <Romain.Baeriswyl@...lis.com>
> Cc: "Mark Rutland" <mark.rutland@....com>, wsa@...-dreams.de, baruch@...s.co.il, "mika westerberg" <mika.westerberg@...ux.intel.com>, "grant likely" <grant.likely@...aro.org>, robh+dt@...nel.org, skuribay@...ox.com, "rafael j wysocki" <rafael.j.wysocki@...el.com>, alan@...ux.intel.com, linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, "delicious quinoa" <delicious.quinoa@...il.com>, dinguyen@...nsource.altera.com, yvanderv@...nsource.altera.com
> Sent: Wednesday, August 20, 2014 4:24:45 PM
> Subject: Re: [PATCH] i2c: designware: deduce speed mode from device tree setting
>
>
>
> On Wed, 20 Aug 2014, Romain Baeriswyl wrote:
>
> > Hi,
> >
> > With the patch "i2c designware add support of I2C standard mode" I already proposed:
> > - I2C standard mode is selected with 100kHz clock frequency.
> > - I2C fast mode is selected with 400kHy clock frequency.
> > - EINVAL error is returned if clock frequency is not 100000 and not 400000.
> >
> > but this patch seems not available yet.
> > What about the other patch "i2c designware make SCL and SDA falling time configurable" ?
> >
> > In i2c-designware_platdrv.c the flag DW_IC_CON_SPEED_xxx is well set
> > depending on the mode:
> >
> > if (clk_freq == 100000)
>
> Romain,
>
> I'm really happy if your patches get accepted. Can this be <= 100000?
> It is really common to run I2C at a lower speed if you have some
> board issues with the i2c bus.
>
> Alan
>
> > dev->master_cfg = DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
> > DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_STD;
> > else
> > dev->master_cfg = DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
> > DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
> >
> >
> > So for me everything should be fine if there patches are applied.
> >
> > Regards,
> >
> > Romain
> >
> > ----- Original Message -----
> > From: "Mark Rutland" <mark.rutland@....com>
> > To: atull@...nsource.altera.com
> > Cc: wsa@...-dreams.de, baruch@...s.co.il, "mika westerberg" <mika.westerberg@...ux.intel.com>, "grant likely" <grant.likely@...aro.org>, robh+dt@...nel.org, skuribay@...ox.com, "Romain Baeriswyl" <Romain.Baeriswyl@...lis.com>, "rafael j wysocki" <rafael.j.wysocki@...el.com>, alan@...ux.intel.com, linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, "delicious quinoa" <delicious.quinoa@...il.com>, dinguyen@...nsource.altera.com, yvanderv@...nsource.altera.com
> > Sent: Wednesday, August 20, 2014 11:22:57 AM
> > Subject: Re: [PATCH] i2c: designware: deduce speed mode from device tree setting
> >
> > On Tue, Aug 19, 2014 at 09:18:49PM +0100, atull@...nsource.altera.com wrote:
> > > From: Alan Tull <atull@...nsource.altera.com>
> > >
> > > Use the documented, but unimplemented "clock-frequency"
> > > Device Tree setting as a guide on whether to set the speed
> > > mode bits in DW_IC_CON to standard or fast i2c mode.
> > >
> > > Previously, the driver was hardwired to fast mode. Default
> > > to fast mode if the "clock-frequency" property is not present
> > > for backwards compatiblity.
> > >
> > > Signed-off-by: Alan Tull <atull@...nsource.altera.com>
> > > ---
> > > drivers/i2c/busses/i2c-designware-platdrv.c | 10 ++++++++--
> > > 1 file changed, 8 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> > > index bc87733..18cd3d9 100644
> > > --- a/drivers/i2c/busses/i2c-designware-platdrv.c
> > > +++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> > > @@ -122,7 +122,8 @@ static int dw_i2c_probe(struct platform_device *pdev)
> > > struct dw_i2c_dev *dev;
> > > struct i2c_adapter *adap;
> > > struct resource *mem;
> > > - int irq, r;
> > > + int irq, r, ret, speed = DW_IC_CON_SPEED_FAST;
> > > + u32 bus_rate;
> > >
> > > irq = platform_get_irq(pdev, 0);
> > > if (irq < 0) {
> > > @@ -167,6 +168,11 @@ static int dw_i2c_probe(struct platform_device *pdev)
> > > of_property_read_u32(pdev->dev.of_node,
> > > "i2c-scl-falling-time-ns",
> > > &dev->scl_falling_time);
> > > +
> > > + ret = of_property_read_u32(pdev->dev.of_node,
> > > + "clock-frequency", &bus_rate);
> > > + if (!ret && (bus_rate <= 100000))
> > > + speed = DW_IC_CON_SPEED_STD;
> >
> > This looks a bit odd.
> >
> > If the device only supports two particular speeds why do we accept any
> > other speed in the clock-frequency property? Surely we should at least
> > warn that something was off?
> >
> > Thanks,
> > Mark
> >
> > > }
> > >
> > > dev->functionality =
> > > @@ -177,7 +183,7 @@ static int dw_i2c_probe(struct platform_device *pdev)
> > > I2C_FUNC_SMBUS_WORD_DATA |
> > > I2C_FUNC_SMBUS_I2C_BLOCK;
> > > dev->master_cfg = DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
> > > - DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
> > > + DW_IC_CON_RESTART_EN | speed;
> > >
> > > /* Try first if we can configure the device from ACPI */
> > > r = dw_i2c_acpi_configure(pdev);
> > > --
> > > 1.7.9.5
> > >
> > > --
> > > To unsubscribe from this list: send the line "unsubscribe devicetree" in
> > > the body of a message to majordomo@...r.kernel.org
> > > More majordomo info at http://vger.kernel.org/majordomo-info.html
> > >
> >
>
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