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i2c: aspeed: add proper support fo 24xx clock params

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24xx BMCs have larger clock divider granularity which can cause problems
when trying to set them as 25xx clock dividers; this adds clock setting
code specific to 24xx.

This also fixes a potential issue where clock dividers were rounded down
instead of up.

Signed-off-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Brendan Higgins 2017-07-28 13:45:58 -07:00 committed by Wolfram Sang
parent 94d3b651c0
commit 87b59ff8d1
1 changed files with 56 additions and 18 deletions
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74
drivers/i2c/busses/i2c-aspeed.c
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@ -132,6 +132,7 @@ 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);
unsigned long parent_clk_frequency;
u32 bus_frequency;
/* Transaction state. */
@ -674,7 +675,7 @@ static const struct i2c_algorithm aspeed_i2c_algo = {
#endif /* CONFIG_I2C_SLAVE */
};
static u32 aspeed_i2c_get_clk_reg_val(u32 divisor)
static u32 aspeed_i2c_get_clk_reg_val(u32 clk_high_low_max, u32 divisor)
{
u32 base_clk, clk_high, clk_low, tmp;
@ -694,16 +695,22 @@ static u32 aspeed_i2c_get_clk_reg_val(u32 divisor)
* Thus,
* SCL_freq = APB_freq /
* ((1 << base_clk) * (clk_high + 1 + clk_low + 1))
* The documentation recommends clk_high >= 8 and clk_low >= 7 when
* possible; this last constraint gives us the following solution:
* 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 > 33 ? ilog2((divisor - 1) / 32) + 1 : 0;
tmp = divisor / (1 << base_clk);
clk_high = tmp / 2 + tmp % 2;
clk_low = tmp - clk_high;
base_clk = 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 (clk_low)
clk_low--;
clk_high -= 1;
clk_low -= 1;
return ((clk_high << ASPEED_I2CD_TIME_SCL_HIGH_SHIFT)
& ASPEED_I2CD_TIME_SCL_HIGH_MASK)
@ -712,13 +719,31 @@ static u32 aspeed_i2c_get_clk_reg_val(u32 divisor)
| (base_clk & ASPEED_I2CD_TIME_BASE_DIVISOR_MASK);
}
static u32 aspeed_i2c_24xx_get_clk_reg_val(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);
}
static u32 aspeed_i2c_25xx_get_clk_reg_val(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);
}
/* precondition: bus.lock has been acquired. */
static int aspeed_i2c_init_clk(struct aspeed_i2c_bus *bus)
{
u32 divisor, clk_reg_val;
divisor = bus->parent_clk_frequency / bus->bus_frequency;
clk_reg_val = aspeed_i2c_get_clk_reg_val(divisor);
divisor = DIV_ROUND_UP(bus->parent_clk_frequency, bus->bus_frequency);
clk_reg_val = bus->get_clk_reg_val(divisor);
writel(clk_reg_val, bus->base + ASPEED_I2C_AC_TIMING_REG1);
writel(ASPEED_NO_TIMEOUT_CTRL, bus->base + ASPEED_I2C_AC_TIMING_REG2);
@ -777,8 +802,22 @@ static int aspeed_i2c_reset(struct aspeed_i2c_bus *bus)
return ret;
}
static const struct of_device_id aspeed_i2c_bus_of_table[] = {
{
.compatible = "aspeed,ast2400-i2c-bus",
.data = aspeed_i2c_24xx_get_clk_reg_val,
},
{
.compatible = "aspeed,ast2500-i2c-bus",
.data = aspeed_i2c_25xx_get_clk_reg_val,
},
{ },
};
MODULE_DEVICE_TABLE(of, aspeed_i2c_bus_of_table);
static int aspeed_i2c_probe_bus(struct platform_device *pdev)
{
const struct of_device_id *match;
struct aspeed_i2c_bus *bus;
struct clk *parent_clk;
struct resource *res;
@ -808,6 +847,12 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
bus->bus_frequency = 100000;
}
match = of_match_node(aspeed_i2c_bus_of_table, pdev->dev.of_node);
if (!match)
bus->get_clk_reg_val = aspeed_i2c_24xx_get_clk_reg_val;
else
bus->get_clk_reg_val = match->data;
/* Initialize the I2C adapter */
spin_lock_init(&bus->lock);
init_completion(&bus->cmd_complete);
@ -869,13 +914,6 @@ static int aspeed_i2c_remove_bus(struct platform_device *pdev)
return 0;
}
static const struct of_device_id aspeed_i2c_bus_of_table[] = {
{ .compatible = "aspeed,ast2400-i2c-bus", },
{ .compatible = "aspeed,ast2500-i2c-bus", },
{ },
};
MODULE_DEVICE_TABLE(of, aspeed_i2c_bus_of_table);
static struct platform_driver aspeed_i2c_bus_driver = {
.probe = aspeed_i2c_probe_bus,
.remove = aspeed_i2c_remove_bus,