From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751960AbaHTPRj (ORCPT ); Wed, 20 Aug 2014 11:17:39 -0400 Received: from mail-bn1blp0187.outbound.protection.outlook.com ([207.46.163.187]:13866 "EHLO na01-bn1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751292AbaHTPRh (ORCPT ); Wed, 20 Aug 2014 11:17:37 -0400 Date: Wed, 20 Aug 2014 10:12:14 -0500 From: atull X-X-Sender: atull@atx-linux-37 To: Romain Baeriswyl CC: Mark Rutland , , , mika westerberg , grant likely , , , rafael j wysocki , , , , , delicious quinoa , , Subject: Re: [PATCH] i2c: designware: deduce speed mode from device tree setting In-Reply-To: <1791089693.2989.1408545513401.JavaMail.root@abilis.com> Message-ID: References: <1791089693.2989.1408545513401.JavaMail.root@abilis.com> User-Agent: Alpine 2.02 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-Originating-IP: [64.129.157.38] X-ClientProxiedBy: BN1PR02CA0045.namprd02.prod.outlook.com (10.141.56.45) To DM2PR03MB317.namprd03.prod.outlook.com (10.141.54.15) X-Microsoft-Antispam: BCL:0;PCL:0;RULEID:;UriScan:; X-Forefront-PRVS: 03094A4065 X-Forefront-Antispam-Report: SFV:NSPM;SFS:(6009001)(189002)(51704005)(164054003)(24454002)(13464003)(199003)(377454003)(101416001)(79102001)(15202345003)(64706001)(46406003)(77096002)(66066001)(83506001)(23726002)(80022001)(15975445006)(53416004)(77982001)(20776003)(46102001)(102836001)(81342001)(76482001)(47776003)(110136001)(107046002)(50466002)(106356001)(81156004)(69596002)(50986999)(33716001)(95666004)(85306004)(99396002)(74502001)(86362001)(74662001)(19580405001)(54356999)(31966008)(76176999)(86152002)(105586002)(42186005)(85852003)(4396001)(83322001)(83072002)(81542001)(87976001)(92566001)(92726001)(19580395003)(21056001)(21314002);DIR:OUT;SFP:;SCL:1;SRVR:DM2PR03MB317;H:atx-linux-37.altera.com;FPR:;MLV:sfv;PTR:InfoNoRecords;MX:1;A:0;LANG:en; X-OriginatorOrg: opensource.altera.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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" > To: "Romain Baeriswyl" > Cc: "Mark Rutland" , wsa@the-dreams.de, baruch@tkos.co.il, "mika westerberg" , "grant likely" , robh+dt@kernel.org, skuribay@pobox.com, "rafael j wysocki" , alan@linux.intel.com, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, "delicious quinoa" , dinguyen@opensource.altera.com, yvanderv@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" > > To: atull@opensource.altera.com > > Cc: wsa@the-dreams.de, baruch@tkos.co.il, "mika westerberg" , "grant likely" , robh+dt@kernel.org, skuribay@pobox.com, "Romain Baeriswyl" , "rafael j wysocki" , alan@linux.intel.com, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, "delicious quinoa" , dinguyen@opensource.altera.com, yvanderv@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, atull@opensource.altera.com wrote: > > > From: Alan Tull > > > > > > 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 > > > --- > > > 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@vger.kernel.org > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > >