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Commit bd698d24 authored by chin.yew.tan@intel.com's avatar chin.yew.tan@intel.com Committed by Wolfram Sang
Browse files

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: default avatarTan Chin Yew <chin.yew.tan@intel.com>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: default avatarJarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 2a03d499

drivers/i2c/busses/i2c-designware-platdrv.c

+22 −9
Original line number Diff line number Diff line
@@ -85,7 +85,6 @@ 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;

	}
@@ -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);

	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);

	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);

		break;

	}



	id = acpi_match_device(pdev->dev.driver->acpi_match_table, &pdev->dev);

	if (id && id->driver_data)