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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>
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1 changed files with 22 additions and 9 deletions
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@ -85,8 +85,7 @@ static void dw_i2c_acpi_params(struct platform_device *pdev, char method[],
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*hcnt = (u16)objs[0].integer.value;
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*lcnt = (u16)objs[1].integer.value;
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if (sda_hold)
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*sda_hold = (u32)objs[2].integer.value;
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*sda_hold = (u32)objs[2].integer.value;
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}
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kfree(buf.pointer);
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@ -105,14 +104,28 @@ static int dw_i2c_acpi_configure(struct platform_device *pdev)
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dev->rx_fifo_depth = 32;
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/*
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* Try to get SDA hold time and *CNT values from an ACPI method if
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* it exists for both supported speed modes.
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* Try to get SDA hold time and *CNT values from an ACPI method for
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* selected speed modes.
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*/
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dw_i2c_acpi_params(pdev, "SSCN", &dev->ss_hcnt, &dev->ss_lcnt, NULL);
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dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev->fs_lcnt,
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&dev->sda_hold_time);
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dw_i2c_acpi_params(pdev, "FPCN", &dev->fp_hcnt, &dev->fp_lcnt, NULL);
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dw_i2c_acpi_params(pdev, "HSCN", &dev->hs_hcnt, &dev->hs_lcnt, NULL);
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switch (dev->clk_freq) {
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case 100000:
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dw_i2c_acpi_params(pdev, "SSCN", &dev->ss_hcnt, &dev->ss_lcnt,
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&dev->sda_hold_time);
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break;
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case 1000000:
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dw_i2c_acpi_params(pdev, "FPCN", &dev->fp_hcnt, &dev->fp_lcnt,
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&dev->sda_hold_time);
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break;
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case 3400000:
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dw_i2c_acpi_params(pdev, "HSCN", &dev->hs_hcnt, &dev->hs_lcnt,
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&dev->sda_hold_time);
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break;
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case 400000:
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default:
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dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev->fs_lcnt,
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&dev->sda_hold_time);
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break;
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}
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id = acpi_match_device(pdev->dev.driver->acpi_match_table, &pdev->dev);
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if (id && id->driver_data)
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