Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754847AbdC1Isv (ORCPT ); Tue, 28 Mar 2017 04:48:51 -0400 Received: from mga03.intel.com ([134.134.136.65]:54583 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754563AbdC1Ist (ORCPT ); Tue, 28 Mar 2017 04:48:49 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.36,236,1486454400"; d="scan'208";a="80089104" From: Tan Chin Yew To: Wolfram Sang , Jarkko Nikula , Andy Shevchenko , Mika Westerberg Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] i2c: designware: Get selected speed mode sda-hold-time via ACPI Date: Tue, 28 Mar 2017 16:48:02 +0800 Message-Id: <1490690882-11623-2-git-send-email-chin.yew.tan@intel.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1490690882-11623-1-git-send-email-chin.yew.tan@intel.com> References: <1490690882-11623-1-git-send-email-chin.yew.tan@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2296 Lines: 62 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 --- 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) -- 1.9.1