1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 6e99d9f56dee..4c1b60539a25 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -53,9 +53,33 @@ static u32 i2c_dw_get_clk_rate_khz(struct dw_i2c_dev *dev)
 }
 
 #ifdef CONFIG_ACPI
+static void dw_i2c_acpi_params(struct platform_device *pdev, char method[],
+                               u16 *hcnt, u16 *lcnt, u32 *sda_hold)
+{
+        struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER };
+        acpi_handle handle = ACPI_HANDLE(&pdev->dev);
+        union acpi_object *obj;
+
+        if (ACPI_FAILURE(acpi_evaluate_object(handle, method, NULL, &buf)))
+                return;
+
+        obj = (union acpi_object *)buf.pointer;
+        if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 3) {
+                const union acpi_object *objs = obj->package.elements;
+
+                *hcnt = (u16)objs[0].integer.value;
+                *lcnt = (u16)objs[1].integer.value;
+                if (sda_hold)
+                        *sda_hold = (u32)objs[2].integer.value;
+        }
+
+        kfree(buf.pointer);
+}
+
 static int dw_i2c_acpi_configure(struct platform_device *pdev)
 {
         struct dw_i2c_dev *dev = platform_get_drvdata(pdev);
+        bool fs_mode = dev->master_cfg & DW_IC_CON_SPEED_FAST;
 
         if (!ACPI_HANDLE(&pdev->dev))
                 return -ENODEV;
@@ -63,6 +87,16 @@ static int dw_i2c_acpi_configure(struct platform_device *pdev)
         dev->adapter.nr = -1;
         dev->tx_fifo_depth = 32;
         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.
+         */
+        dw_i2c_acpi_params(pdev, "SSCN", &dev->ss_hcnt, &dev->ss_lcnt,
+                           fs_mode ? NULL : &dev->sda_hold_time);
+        dw_i2c_acpi_params(pdev, "FMCN", &dev->fs_hcnt, &dev->fs_lcnt,
+                           fs_mode ? &dev->sda_hold_time : NULL);
+
         return 0;
 }