From mboxrd@z Thu Jan 1 00:00:00 1970 From: atull Subject: Re: [PATCH] i2c designware add support of I2C standard mode Date: Wed, 20 Aug 2014 09:32:49 -0500 Message-ID: References: <20140820124231.GD21734@leverpostej> <1408544948-22339-1-git-send-email-romainba@abilis.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Return-path: In-Reply-To: <1408544948-22339-1-git-send-email-romainba-ux6zf3SgZrrQT0dZR+AlfA@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Romain Baeriswyl Cc: Wolfram Sang , Mika Westerberg , Christian Ruppert , "Rafael J. Wysocki" , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Mark Rutland , baruch-NswTu9S1W3P6gbPvEgmw2w@public.gmane.org, grant.likely-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org, robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, skuribay-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org, alan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, delicious.quinoa-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, dinguyen-yzvPICuk2ABMcg4IHK0kFoH6Mc4MB0Vx@public.gmane.org, yvanderv-yzvPICuk2ABMcg4IHK0kFoH6Mc4MB0Vx@public.gmane.org, Romain Baeriswyl List-Id: linux-i2c@vger.kernel.org On Wed, 20 Aug 2014, Romain Baeriswyl wrote: > From: Romain Baeriswyl > > Some legacy devices support ony I2C standard mode at 100kHz. > This patch allows to select the standard mode through the DTS > with the use of the existing clock-frequency parameter. > > When clock-frequency parameter is not set, the fast mode is selected. > Only when the parameter is set at 100000, the standard mode is selected. > > Signed-off-by: Romain Baeriswyl > Reviewed-by: Christian Ruppert > --- > drivers/i2c/busses/i2c-designware-platdrv.c | 23 +++++++++++++++++++++-- > 1 files changed, 21 insertions(+), 2 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c > index 402ec39..b543fe1 100644 > --- a/drivers/i2c/busses/i2c-designware-platdrv.c > +++ b/drivers/i2c/busses/i2c-designware-platdrv.c > @@ -122,6 +122,7 @@ static int dw_i2c_probe(struct platform_device *pdev) > struct i2c_adapter *adap; > struct resource *mem; > int irq, r; > + u32 clk_freq; > > irq = platform_get_irq(pdev, 0); > if (irq < 0) { > @@ -151,6 +152,9 @@ static int dw_i2c_probe(struct platform_device *pdev) > return PTR_ERR(dev->clk); > clk_prepare_enable(dev->clk); > > + /* fast mode by default because of legacy reasons */ > + clk_freq = 400000; > + > if (pdev->dev.of_node) { > u32 ht = 0; > u32 ic_clk = dev->get_clk_rate_khz(dev); > @@ -166,6 +170,17 @@ 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); > + > + of_property_read_u32(pdev->dev.of_node, "clock-frequency", > + &clk_freq); > + > + /* Only standard mode at 100kHz and fast mode at 400kHz > + * are supported. > + */ > + if (clk_freq != 100000 && clk_freq != 400000) { > + dev_err(&pdev->dev, "Only 100kHz and 400kHz supported"); > + return -EINVAL; > + } Hi Romain, It is common to operate i2c at <100KHz on boards that have i2c issues. I am using this driver at 50KHz because I have a LCD module that just doesn't work at a full 100KHz. Please remove the check for these two frequency points. > } > > dev->functionality = > @@ -175,8 +190,12 @@ static int dw_i2c_probe(struct platform_device *pdev) > I2C_FUNC_SMBUS_BYTE_DATA | > 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; > + if (clk_freq == 100000) Please change to <= > + 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; > > /* Try first if we can configure the device from ACPI */ > r = dw_i2c_acpi_configure(pdev); > -- > 1.7.1 > >