i2c: designware: Round down ACPI provided clk to nearest supported clk

The Lenovo Miix2 8 DSDT contains an i2c clk / bus speed of 1700000 Hz
for one if its devices, which is not supported.

This is the second DSDT to show up with an unsupported clk in a short
time, remove the hardcoded fix for DSDTs with a 1 MiHz clock and simply
always round down the clk to the nearest supported value.

Reported-by: russianneuromancer@ya.ru
Fixes: 682c6c2188 ("i2c: designware: Some broken DSTDs use 1MiHz ...")
Signed-off-by: Hans de Goede <hdegoede@redhat.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 57248bccadbcb73df29b224594b66bf8088cfb30..2b98a173136f2e53d729dfbe7fe314fe1eaf07fc 100644 (file)
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -256,7 +256,8 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
        struct dw_i2c_dev *dev;
        u32 acpi_speed, ht = 0;
        struct resource *mem;
-       int irq, ret;
+       int i, irq, ret;
+       const int supported_speeds[] = { 0, 100000, 400000, 1000000, 3400000 };
 
        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
@@ -297,9 +298,16 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
        }
 
        acpi_speed = i2c_acpi_find_bus_speed(&pdev->dev);
-       /* Some broken DSTDs use 1MiHz instead of 1MHz */
-       if (acpi_speed == 1048576)
-               acpi_speed = 1000000;
+       /*
+        * Some DSTDs use a non standard speed, round down to the lowest
+        * standard speed.
+        */
+       for (i = 1; i < ARRAY_SIZE(supported_speeds); i++) {
+               if (acpi_speed < supported_speeds[i])
+                       break;
+       }
+       acpi_speed = supported_speeds[i - 1];
+
        /*
         * Find bus speed from the "clock-frequency" device property, ACPI
         * or by using fast mode if neither is set.