i2c: meson: use full 12 bits for clock divider

The clock divider has 12 bits, splitted into a 10 bit field and a
2 bit field. The extra 2 bits aren't used currently.

Change this to use the full 12 bits and warn if the requested
frequency is too low.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Acked-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/busses/i2c-meson.c b/drivers/i2c/busses/i2c-meson.c
index 852db0f0bec29d03ab56fba7e422ceda55947a10..abaa7cae0936efc7339580374002f815c52b2dae 100644 (file)
--- a/drivers/i2c/busses/i2c-meson.c
+++ b/drivers/i2c/busses/i2c-meson.c
@@ -35,7 +35,9 @@
 #define REG_CTRL_STATUS                BIT(2)
 #define REG_CTRL_ERROR         BIT(3)
 #define REG_CTRL_CLKDIV_SHIFT  12
-#define REG_CTRL_CLKDIV_MASK   ((BIT(10) - 1) << REG_CTRL_CLKDIV_SHIFT)
+#define REG_CTRL_CLKDIV_MASK   GENMASK(21, 12)
+#define REG_CTRL_CLKDIVEXT_SHIFT 28
+#define REG_CTRL_CLKDIVEXT_MASK        GENMASK(29, 28)
 
 #define I2C_TIMEOUT_MS         500
 
@@ -134,8 +136,18 @@ static void meson_i2c_set_clk_div(struct meson_i2c *i2c, unsigned int freq)
        unsigned int div;
 
        div = DIV_ROUND_UP(clk_rate, freq * 4);
+
+       /* clock divider has 12 bits */
+       if (div >= (1 << 12)) {
+               dev_err(i2c->dev, "requested bus frequency too low\n");
+               div = (1 << 12) - 1;
+       }
+
        meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_CLKDIV_MASK,
-                          div << REG_CTRL_CLKDIV_SHIFT);
+                          (div & GENMASK(9, 0)) << REG_CTRL_CLKDIV_SHIFT);
+
+       meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_CLKDIVEXT_MASK,
+                          (div >> 10) << REG_CTRL_CLKDIVEXT_SHIFT);
 
        dev_dbg(i2c->dev, "%s: clk %lu, freq %u, div %u\n", __func__,
                clk_rate, freq, div);