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>

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index a597ba32de7e4bab125c5f09450006bab2320250..5a4eb6b6bd9295b0b0acfbd3ace526947d686647 100644 (file)
--- 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)