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
----- Original Message -----
From: "atull" <at...@opensource.altera.com>
To: "Romain Baeriswyl" <romain.baeris...@abilis.com>
Cc: "Mark Rutland" <mark.rutl...@arm.com>, w...@the-dreams.de,
bar...@tkos.co.il, "mika westerberg" <mika.westerb...@linux.intel.com>, "grant
likely" <grant.lik...@linaro.org>, robh...@kernel.org, skuri...@pobox.com,
"rafael j wysocki" <rafael.j.wyso...@intel.com>, a...@linux.intel.com,
linux-i2c@vger.kernel.org, linux-ker...@vger.kernel.org,
devicet...@vger.kernel.org, "delicious quinoa" <delicious.qui...@gmail.com>,
dingu...@opensource.altera.com, yvand...@opensource.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.rutl...@arm.com>
> To: at...@opensource.altera.com
> Cc: w...@the-dreams.de, bar...@tkos.co.il, "mika westerberg"
> <mika.westerb...@linux.intel.com>, "grant likely" <grant.lik...@linaro.org>,
> robh...@kernel.org, skuri...@pobox.com, "Romain Baeriswyl"
> <romain.baeris...@abilis.com>, "rafael j wysocki"
> <rafael.j.wyso...@intel.com>, a...@linux.intel.com,
> linux-i2c@vger.kernel.org, linux-ker...@vger.kernel.org,
> devicet...@vger.kernel.org, "delicious quinoa" <delicious.qui...@gmail.com>,
> dingu...@opensource.altera.com, yvand...@opensource.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, at...@opensource.altera.com wrote:
> > From: Alan Tull <at...@opensource.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 <at...@opensource.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
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> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
>
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