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i2c: designware: Get selected speed mode sda-hold-time via ACPI

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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>
This commit is contained in:
chin.yew.tan@intel.com 2017-03-28 16:48:02 +08:00 committed by Wolfram Sang
parent 2a03d49922
commit bd698d24b1
1 changed files with 22 additions and 9 deletions
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31
drivers/i2c/busses/i2c-designware-platdrv.c
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@ -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)