lkml.org 
[lkml]   [2017]   [Jul]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 1/1] i2c: aspeed: add proper support fo 24xx clock params
Date
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>
---
Changes for v2:
- Fixed off by one error to check for divisors with base_clk == 0
- Simplified some of the divisor math
---
drivers/i2c/busses/i2c-aspeed.c | 74 +++++++++++++++++++++++++++++++----------
1 file changed, 56 insertions(+), 18 deletions(-)

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index f19348328a71..60afab866494 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -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,
--
2.14.0.rc0.400.g1c36432dff-goog
\
 
 \ /
  Last update: 2017-07-28 22:47    [W:0.081 / U:1.920 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site