[v4,05/10] i2c: meson: use full 12 bits for clock divider

Message ID fbc241ed-ec1e-b433-50af-5d0ebca09711@gmail.com
State Superseded
Headers show

Commit Message

Heiner Kallweit March 14, 2017, 9:51 p.m.
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>
---
v2:
- added Acked-by
v3:
- changed order of patches
v4:
- no changes
---
 drivers/i2c/busses/i2c-meson.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

Comments

Wolfram Sang March 23, 2017, 8:34 p.m. | #1
> +	/* clock divider has 12 bits */
> +	WARN_ON(div >= (1 << 12));

Do you insist on WARN_ON? I wonder what it gives over dev_err?
Heiner Kallweit March 24, 2017, 6:49 a.m. | #2
Am 23.03.2017 um 21:34 schrieb Wolfram Sang:
> 
>> +	/* clock divider has 12 bits */
>> +	WARN_ON(div >= (1 << 12));
> 
> Do you insist on WARN_ON? I wonder what it gives over dev_err?
> 
Right, as we just read the bus frequency from DT there's not
really a benefit in seeing the call trace. I'll change it.

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Patch

diff --git a/drivers/i2c/busses/i2c-meson.c b/drivers/i2c/busses/i2c-meson.c
index ac0ac82d..03f70282 100644
--- 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 +136,15 @@  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 */
+	WARN_ON(div >= (1 << 12));
+
 	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);