From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI Date: Tue, 14 Feb 2017 12:05:06 +0200 Message-ID: <1487066706.2133.465.camel@linux.intel.com> References: <1487051641-31927-1-git-send-email-chin.yew.tan@intel.com> <1487051641-31927-2-git-send-email-chin.yew.tan@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Return-path: Received: from mga02.intel.com ([134.134.136.20]:54891 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751921AbdBNKGm (ORCPT ); Tue, 14 Feb 2017 05:06:42 -0500 In-Reply-To: <1487051641-31927-2-git-send-email-chin.yew.tan@intel.com> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: chin.yew.tan@intel.com, jarkko.nikula@linux.intel.com, mika.westerberg@linux.intel.com Cc: linux-i2c@vger.kernel.org On Tue, 2017-02-14 at 13:54 +0800, chin.yew.tan@intel.com wrote: > From: Tan Chin Yew > > Sda-hold-time is an important parameter for tuning i2c to meet the > electrical specification especially for high speed. I2C with incorrect > sda-hold-time may cause lost arbitration error. Now, the driver is > able to > get sda-hold-time for all the speed supported. > Reviewed-by: Andy Shevchenko > Signed-off-by: Tan Chin Yew > --- >  drivers/i2c/busses/i2c-designware-platdrv.c | 28 > +++++++++++++++++++++------- >  1 file changed, 21 insertions(+), 7 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c > b/drivers/i2c/busses/i2c-designware-platdrv.c > index 6ce4313..00c880a 100644 > --- a/drivers/i2c/busses/i2c-designware-platdrv.c > +++ b/drivers/i2c/busses/i2c-designware-platdrv.c > @@ -101,14 +101,28 @@ static int dw_i2c_acpi_configure(struct > platform_device *pdev) >   dev->rx_fifo_depth = 32; >   >   /* > -  * Try to get SDA hold time and *CNT values from an ACPI > method if > -  * it exists for both supported speed modes. > +  * Try to get SDA hold time and *CNT values from an ACPI > method for > +  * selected speed modes. >    */ > - dw_i2c_acpi_params(pdev, "SSCN", &dev->ss_hcnt, &dev- > >ss_lcnt, NULL); > - dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev- > >fs_lcnt, > -    &dev->sda_hold_time); > - dw_i2c_acpi_params(pdev, "FPCN", &dev->fp_hcnt, &dev- > >fp_lcnt, NULL); > - dw_i2c_acpi_params(pdev, "HSCN", &dev->hs_hcnt, &dev- > >hs_lcnt, NULL); > + switch (dev->clk_freq) { > + case 100000: > + dw_i2c_acpi_params(pdev, "SSCN", &dev->ss_hcnt, &dev- > >ss_lcnt, > +    &dev->sda_hold_time); > + break; > + case 1000000: > + dw_i2c_acpi_params(pdev, "FPCN", &dev->fp_hcnt, &dev- > >fp_lcnt, > +    &dev->sda_hold_time); > + break; > + case 3400000: > + dw_i2c_acpi_params(pdev, "HSCN", &dev->hs_hcnt, &dev- > >hs_lcnt, > +    &dev->sda_hold_time); > + break; > + case 400000: > + default: > + dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev- > >fs_lcnt, > +    &dev->sda_hold_time); > + break; > + } >   >   id = acpi_match_device(pdev->dev.driver->acpi_match_table, > &pdev->dev); >   if (id && id->driver_data) -- Andy Shevchenko Intel Finland Oy