@@ -142,7 +142,8 @@ struct aspeed_i2c_bus {
/* Synchronizes I/O mem access to base. */
spinlock_t lock;
struct completion cmd_complete;
- u32 (*get_clk_reg_val)(u32 divisor);
+ u32 (*get_clk_reg_val)(struct device *dev,
+ u32 divisor);
unsigned long parent_clk_frequency;
u32 bus_frequency;
/* Transaction state. */
@@ -705,16 +706,27 @@ static const struct i2c_algorithm aspeed_i2c_algo = {
#endif /* CONFIG_I2C_SLAVE */
};
-static u32 aspeed_i2c_get_clk_reg_val(u32 clk_high_low_max, u32 divisor)
+static u32 aspeed_i2c_get_clk_reg_val(struct device *dev,
+ u32 clk_high_low_mask,
+ u32 divisor)
{
- u32 base_clk, clk_high, clk_low, tmp;
+ u32 base_clk_divisor, clk_high_low_max, clk_high, clk_low, tmp;
+
+ /*
+ * SCL_high and SCL_low represent a value 1 greater than what is stored
+ * since a zero divider is meaningless. Thus, the max value each can
+ * store is every bit set + 1. Since SCL_high and SCL_low are added
+ * together (see below), the max value of both is the max value of one
+ * them times two.
+ */
+ clk_high_low_max = (clk_high_low_mask + 1) * 2;
/*
* The actual clock frequency of SCL is:
* SCL_freq = APB_freq / (base_freq * (SCL_high + SCL_low))
* = APB_freq / divisor
* where base_freq is a programmable clock divider; its value is
- * base_freq = 1 << base_clk
+ * base_freq = 1 << base_clk_divisor
* SCL_high is the number of base_freq clock cycles that SCL stays high
* and SCL_low is the number of base_freq clock cycles that SCL stays
* low for a period of SCL.
@@ -724,47 +736,59 @@ static u32 aspeed_i2c_get_clk_reg_val(u32 clk_high_low_max, u32 divisor)
* SCL_low = clk_low + 1
* Thus,
* SCL_freq = APB_freq /
- * ((1 << base_clk) * (clk_high + 1 + clk_low + 1))
+ * ((1 << base_clk_divisor) * (clk_high + 1 + clk_low + 1))
* The documentation recommends clk_high >= clk_high_max / 2 and
* clk_low >= clk_low_max / 2 - 1 when possible; this last constraint
* gives us the following solution:
*/
- base_clk = divisor > clk_high_low_max ?
+ base_clk_divisor = divisor > clk_high_low_max ?
ilog2((divisor - 1) / clk_high_low_max) + 1 : 0;
- tmp = (divisor + (1 << base_clk) - 1) >> base_clk;
- clk_low = tmp / 2;
- clk_high = tmp - clk_low;
- if (clk_high)
- clk_high--;
+ if (base_clk_divisor > ASPEED_I2CD_TIME_BASE_DIVISOR_MASK) {
+ base_clk_divisor = ASPEED_I2CD_TIME_BASE_DIVISOR_MASK;
+ clk_low = clk_high_low_mask;
+ clk_high = clk_high_low_mask;
+ dev_err(dev,
+ "clamping clock divider: divider requested, %u, is greater than largest possible divider, %u.",
+ divisor, (1 << base_clk_divisor) * clk_high_low_max);
+ } else {
+ tmp = (divisor + (1 << base_clk_divisor) - 1)
+ >> base_clk_divisor;
+ clk_low = tmp / 2;
+ clk_high = tmp - clk_low;
+
+ if (clk_high)
+ clk_high--;
- if (clk_low)
- clk_low--;
+ if (clk_low)
+ clk_low--;
+ }
return ((clk_high << ASPEED_I2CD_TIME_SCL_HIGH_SHIFT)
& ASPEED_I2CD_TIME_SCL_HIGH_MASK)
| ((clk_low << ASPEED_I2CD_TIME_SCL_LOW_SHIFT)
& ASPEED_I2CD_TIME_SCL_LOW_MASK)
- | (base_clk & ASPEED_I2CD_TIME_BASE_DIVISOR_MASK);
+ | (base_clk_divisor
+ & ASPEED_I2CD_TIME_BASE_DIVISOR_MASK);
}
-static u32 aspeed_i2c_24xx_get_clk_reg_val(u32 divisor)
+static u32 aspeed_i2c_24xx_get_clk_reg_val(struct device *dev, u32 divisor)
{
/*
* clk_high and clk_low are each 3 bits wide, so each can hold a max
* value of 8 giving a clk_high_low_max of 16.
*/
- return aspeed_i2c_get_clk_reg_val(16, divisor);
+ return aspeed_i2c_get_clk_reg_val(dev, GENMASK(2, 0), divisor);
}
-static u32 aspeed_i2c_25xx_get_clk_reg_val(u32 divisor)
+static u32 aspeed_i2c_25xx_get_clk_reg_val(struct device *dev, u32 divisor)
{
/*
* clk_high and clk_low are each 4 bits wide, so each can hold a max
* value of 16 giving a clk_high_low_max of 32.
*/
- return aspeed_i2c_get_clk_reg_val(32, divisor);
+ return aspeed_i2c_get_clk_reg_val(dev, GENMASK(3, 0), divisor);
}
/* precondition: bus.lock has been acquired. */
@@ -777,7 +801,7 @@ static int aspeed_i2c_init_clk(struct aspeed_i2c_bus *bus)
clk_reg_val &= (ASPEED_I2CD_TIME_TBUF_MASK |
ASPEED_I2CD_TIME_THDSTA_MASK |
ASPEED_I2CD_TIME_TACST_MASK);
- clk_reg_val |= bus->get_clk_reg_val(divisor);
+ clk_reg_val |= bus->get_clk_reg_val(bus->dev, divisor);
writel(clk_reg_val, bus->base + ASPEED_I2C_AC_TIMING_REG1);
writel(ASPEED_NO_TIMEOUT_CTRL, bus->base + ASPEED_I2C_AC_TIMING_REG2);