diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c index 9d6f02265a1b..8dc9161ced38 100644 --- a/drivers/i2c/busses/i2c-aspeed.c +++ b/drivers/i2c/busses/i2c-aspeed.c @@ -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. */ @@ -710,16 +711,27 @@ 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. @@ -729,47 +741,59 @@ 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.\n", + 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_low) - clk_low--; + if (clk_high) + clk_high--; + + 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. */ @@ -782,7 +806,7 @@ 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); @@ -898,7 +922,8 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev) if (!match) bus->get_clk_reg_val = aspeed_i2c_24xx_get_clk_reg_val; else - bus->get_clk_reg_val = (u32 (*)(u32))match->data; + bus->get_clk_reg_val = (u32 (*)(struct device *, u32)) + match->data; /* Initialize the I2C adapter */ spin_lock_init(&bus->lock);