From bd698d24b1b5790d0a22d44a0705dabd47235ad4 Mon Sep 17 00:00:00 2001
From: "chin.yew.tan@intel.com" <chin.yew.tan@intel.com>
Date: Tue, 28 Mar 2017 16:48:02 +0800
Subject: [PATCH] i2c: designware: Get selected speed mode sda-hold-time via
ACPI
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 <chin.yew.tan@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
---
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 a597ba32de7e4..5a4eb6b6bd929 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)
--
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