i2c: designware: fix wrong Tx/Rx FIFO for ACPI

ACPI always sets Tx/Rx FIFO to 32. This configuration will
cause problem if the IP core supports a FIFO size of less than 32.
The driver should read the FIFO size from the IP and select the smaller
one of the two.

Signed-off-by: Tin Huynh <tnhuynh@apm.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@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 08153ea..6ce4313 100644 (file)
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -150,6 +150,29 @@ static int i2c_dw_plat_prepare_clk(struct dw_i2c_dev *i_dev, bool prepare)
        return 0;
 }
 
+static void dw_i2c_set_fifo_size(struct dw_i2c_dev *dev, int id)
+{
+       u32 param, tx_fifo_depth, rx_fifo_depth;
+
+       /*
+        * Try to detect the FIFO depth if not set by interface driver,
+        * the depth could be from 2 to 256 from HW spec.
+        */
+       param = i2c_dw_read_comp_param(dev);
+       tx_fifo_depth = ((param >> 16) & 0xff) + 1;
+       rx_fifo_depth = ((param >> 8)  & 0xff) + 1;
+       if (!dev->tx_fifo_depth) {
+               dev->tx_fifo_depth = tx_fifo_depth;
+               dev->rx_fifo_depth = rx_fifo_depth;
+               dev->adapter.nr = id;
+       } else if (tx_fifo_depth >= 2) {
+               dev->tx_fifo_depth = min_t(u32, dev->tx_fifo_depth,
+                               tx_fifo_depth);
+               dev->rx_fifo_depth = min_t(u32, dev->rx_fifo_depth,
+                               rx_fifo_depth);
+       }
+}
+
 static int dw_i2c_plat_probe(struct platform_device *pdev)
 {
        struct dw_i2c_platform_data *pdata = dev_get_platdata(&pdev->dev);
@@ -245,13 +268,7 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
                                1000000);
        }
 
-       if (!dev->tx_fifo_depth) {
-               u32 param1 = i2c_dw_read_comp_param(dev);
-
-               dev->tx_fifo_depth = ((param1 >> 16) & 0xff) + 1;
-               dev->rx_fifo_depth = ((param1 >> 8)  & 0xff) + 1;
-               dev->adapter.nr = pdev->id;
-       }
+       dw_i2c_set_fifo_size(dev, pdev->id);
 
        adap = &dev->adapter;
        adap->owner = THIS_MODULE;