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, 28 Mar 2017 12:13:46 +0300 Message-ID: <1490692426.708.26.camel@linux.intel.com> References: <1490690882-11623-1-git-send-email-chin.yew.tan@intel.com> <1490690882-11623-2-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 mga07.intel.com ([134.134.136.100]:43914 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754855AbdC1JQs (ORCPT ); Tue, 28 Mar 2017 05:16:48 -0400 In-Reply-To: <1490690882-11623-2-git-send-email-chin.yew.tan@intel.com> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Tan Chin Yew , Wolfram Sang , Jarkko Nikula , Mika Westerberg Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org On Tue, 2017-03-28 at 16:48 +0800, Tan Chin Yew wrote: > 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. Instead of loading all > speed mode settings, only selected speed mode settings are loaded. > > Signed-off-by: Tan Chin Yew Looks good to me: Reviewed-by: Andy Shevchenko > --- >  drivers/i2c/busses/i2c-designware-platdrv.c | 31 > ++++++++++++++++++++--------- >  1 file changed, 22 insertions(+), 9 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c > b/drivers/i2c/busses/i2c-designware-platdrv.c > index a597ba32..5a4eb6b 100644 > --- a/drivers/i2c/busses/i2c-designware-platdrv.c > +++ b/drivers/i2c/busses/i2c-designware-platdrv.c > @@ -85,8 +85,7 @@ static void dw_i2c_acpi_params(struct > platform_device *pdev, char method[], >   >   *hcnt = (u16)objs[0].integer.value; >   *lcnt = (u16)objs[1].integer.value; > - if (sda_hold) > - *sda_hold = (u32)objs[2].integer.value; > + *sda_hold = (u32)objs[2].integer.value; >   } >   >   kfree(buf.pointer); > @@ -105,14 +104,28 @@ 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