[PATCH V2 4/7] i2c: sprd: Add I2C controller driver to support dynamic switching of 400K/1M/3.4M frequency

Huangzheng Lai
2023-10-23T08:13:30Z

When I2C-slaves supporting different frequencies use the same I2C
controller, the I2C controller usually only operates at lower frequencies.
In order to improve the performance of I2C-slaves transmission supporting
faster frequencies, we dynamically configure the I2C operating frequency
based on the value of the input parameter msg ->flag.

Signed-off-by: Huangzheng Lai <Huangzheng.Lai@unisoc.com>
---
drivers/i2c/busses/i2c-sprd.c | 101 +++++++++++++++++++---------------
1 file changed, 57 insertions(+), 44 deletions(-)

diff --git a/drivers/i2c/busses/i2c-sprd.c b/drivers/i2c/busses/i2c-sprd.c
index dec627ef408c..f1f7fad42ecd 100644
--- a/drivers/i2c/busses/i2c-sprd.c
+++ b/drivers/i2c/busses/i2c-sprd.c
@@ -75,7 +75,14 @@
#define SPRD_I2C_PM_TIMEOUT 1000
/* timeout (ms) for transfer message */
#define I2C_XFER_TIMEOUT 1000
-
+/* dynamic modify clk_freq flag */
+#define I2C_3M4_FLAG 0x0100
+#define I2C_1M_FLAG 0x0080
+#define I2C_400K_FLAG 0x0040
+
+#define I2C_FREQ_400K 400000
+#define I2C_FREQ_1M 1000000
+#define I2C_FREQ_3_4M 3400000
/* SPRD i2c data structure */
struct sprd_i2c {
struct i2c_adapter adap;
@@ -94,6 +101,49 @@ struct sprd_i2c {
int err;
};

+static void sprd_i2c_set_clk(struct sprd_i2c *i2c_dev, u32 freq)
+{
+ u32 apb_clk = i2c_dev->src_clk;
+ /*
+ * From I2C databook, the prescale calculation formula:
+ * prescale = freq_i2c / (4 * freq_scl) - 1;
+ */
+ u32 i2c_dvd = apb_clk / (4 * freq) - 1;
+ /*
+ * From I2C databook, the high period of SCL clock is recommended as
+ * 40% (2/5), and the low period of SCL clock is recommended as 60%
+ * (3/5), then the formula should be:
+ * high = (prescale * 2 * 2) / 5
+ * low = (prescale * 2 * 3) / 5
+ */
+ u32 high = ((i2c_dvd << 1) * 2) / 5;
+ u32 low = ((i2c_dvd << 1) * 3) / 5;
+ u32 div0 = I2C_ADDR_DVD0_CALC(high, low);
+ u32 div1 = I2C_ADDR_DVD1_CALC(high, low);
+
+ writel(div0, i2c_dev->base + ADDR_DVD0);
+ writel(div1, i2c_dev->base + ADDR_DVD1);
+
+ /* Start hold timing = hold time(us) * source clock */
+ switch (freq) {
+ case I2C_MAX_STANDARD_MODE_FREQ:
+ writel((4 * apb_clk) / 1000000, i2c_dev->base + ADDR_STA0_DVD);
+ break;
+ case I2C_MAX_FAST_MODE_FREQ:
+ writel((6 * apb_clk) / 10000000, i2c_dev->base + ADDR_STA0_DVD);
+ break;
+ case I2C_MAX_FAST_MODE_PLUS_FREQ:
+ writel((8 * apb_clk) / 10000000, i2c_dev->base + ADDR_STA0_DVD);
+ break;
+ case I2C_MAX_HIGH_SPEED_MODE_FREQ:
+ writel((8 * apb_clk) / 10000000, i2c_dev->base + ADDR_STA0_DVD);
+ break;
+ default:
+ dev_err(i2c_dev->dev, "Unsupported frequency: %d\n", freq);
+ break;
+ }
+}
+
static void sprd_i2c_set_count(struct sprd_i2c *i2c_dev, u32 count)
{
writel(count, i2c_dev->base + I2C_COUNT);
@@ -269,6 +319,12 @@ static int sprd_i2c_handle_msg(struct i2c_adapter *i2c_adap,
sprd_i2c_send_stop(i2c_dev, !!is_last_msg);
}

+ if (msg->flags & I2C_400K_FLAG)
+ sprd_i2c_set_clk(i2c_dev, I2C_FREQ_400K);
+ else if (msg->flags & I2C_1M_FLAG)
+ sprd_i2c_set_clk(i2c_dev, I2C_FREQ_1M);
+ else if (msg->flags & I2C_3M4_FLAG)
+ sprd_i2c_set_clk(i2c_dev, I2C_FREQ_3_4M);
/*
* We should enable rx fifo full interrupt to get data when receiving
* full data.
@@ -331,49 +387,6 @@ static const struct i2c_algorithm sprd_i2c_algo = {
.functionality = sprd_i2c_func,
};

-static void sprd_i2c_set_clk(struct sprd_i2c *i2c_dev, u32 freq)
-{
- u32 apb_clk = i2c_dev->src_clk;
- /*
- * From I2C databook, the prescale calculation formula:
- * prescale = freq_i2c / (4 * freq_scl) - 1;
- */
- u32 i2c_dvd = apb_clk / (4 * freq) - 1;
- /*
- * From I2C databook, the high period of SCL clock is recommended as
- * 40% (2/5), and the low period of SCL clock is recommended as 60%
- * (3/5), then the formula should be:
- * high = (prescale * 2 * 2) / 5
- * low = (prescale * 2 * 3) / 5
- */
- u32 high = ((i2c_dvd << 1) * 2) / 5;
- u32 low = ((i2c_dvd << 1) * 3) / 5;
- u32 div0 = I2C_ADDR_DVD0_CALC(high, low);
- u32 div1 = I2C_ADDR_DVD1_CALC(high, low);
-
- writel(div0, i2c_dev->base + ADDR_DVD0);
- writel(div1, i2c_dev->base + ADDR_DVD1);
-
- /* Start hold timing = hold time(us) * source clock */
- switch (freq) {
- case I2C_MAX_STANDARD_MODE_FREQ:
- writel((4 * apb_clk) / 1000000, i2c_dev->base + ADDR_STA0_DVD);
- break;
- case I2C_MAX_FAST_MODE_FREQ:
- writel((6 * apb_clk) / 10000000, i2c_dev->base + ADDR_STA0_DVD);
- break;
- case I2C_MAX_FAST_MODE_PLUS_FREQ:
- writel((8 * apb_clk) / 10000000, i2c_dev->base + ADDR_STA0_DVD);
- break;
- case I2C_MAX_HIGH_SPEED_MODE_FREQ:
- writel((8 * apb_clk) / 10000000, i2c_dev->base + ADDR_STA0_DVD);
- break;
- default:
- dev_err(i2c_dev->dev, "Unsupported frequency: %d\n", freq);
- break;
- }
-}
-
static void sprd_i2c_enable(struct sprd_i2c *i2c_dev)
{
u32 tmp = I2C_DVD_OPT;
--
2.17.1