[PATCH 2/2 v4] hwmon: (aspeed-pwm-tacho) Poll with short sleeps.

Patrick Venture
2017-06-24T03:39:59Z

The reference driver polled but mentioned it was possible to sleep
for a computed period to know when it's ready to read. However, polling
with minimal sleeps is quick and works. This also improves responsiveness
from the driver.

Testing: tested on ast2400 on quanta-q71l

Signed-off-by: Patrick Venture <venture@google.com>
---
v4: Added missing change log
v3: Added missing return value check
v2: Fixed poll to sleep instead of an increment loop
---
drivers/hwmon/aspeed-pwm-tacho.c | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/drivers/hwmon/aspeed-pwm-tacho.c b/drivers/hwmon/aspeed-pwm-tacho.c
index b2ab5612d8a4..cfcd769175e6 100644
--- a/drivers/hwmon/aspeed-pwm-tacho.c
+++ b/drivers/hwmon/aspeed-pwm-tacho.c
@@ -163,6 +163,9 @@
#define M_TACH_UNIT 0x00c0
#define INIT_FAN_CTRL 0xFF

+/* How long we sleep in us while waiting for an RPM result. */
+#define ASPEED_RPM_STATUS_SLEEP_USEC 500
+
struct aspeed_pwm_tacho_data {
struct regmap *regmap;
unsigned long clk_freq;
@@ -508,8 +511,9 @@ static u32 aspeed_get_fan_tach_ch_measure_period(struct aspeed_pwm_tacho_data
static int aspeed_get_fan_tach_ch_rpm(struct aspeed_pwm_tacho_data *priv,
u8 fan_tach_ch)
{
- u32 raw_data, tach_div, clk_source, sec, val;
+ u32 raw_data, tach_div, clk_source, msec, usec, val;
u8 fan_tach_ch_source, type, mode, both;
+ int ret;

regmap_write(priv->regmap, ASPEED_PTCR_TRIGGER, 0);
regmap_write(priv->regmap, ASPEED_PTCR_TRIGGER, 0x1 << fan_tach_ch);
@@ -517,12 +521,20 @@ static int aspeed_get_fan_tach_ch_rpm(struct aspeed_pwm_tacho_data *priv,
fan_tach_ch_source = priv->fan_tach_ch_source[fan_tach_ch];
type = priv->pwm_port_type[fan_tach_ch_source];

- sec = (1000 / aspeed_get_fan_tach_ch_measure_period(priv, type));
- msleep(sec);
+ msec = (1000 / aspeed_get_fan_tach_ch_measure_period(priv, type));
+ usec = msec * 1000;
+
+ ret = regmap_read_poll_timeout(
+ priv->regmap,
+ ASPEED_PTCR_RESULT,
+ val,
+ (val & RESULT_STATUS_MASK),
+ ASPEED_RPM_STATUS_SLEEP_USEC,
+ usec);

- regmap_read(priv->regmap, ASPEED_PTCR_RESULT, &val);
- if (!(val & RESULT_STATUS_MASK))
- return -ETIMEDOUT;
+ /* return -ETIMEDOUT if we didn't get an answer. */
+ if (ret)
+ return ret;

raw_data = val & RESULT_VALUE_MASK;
tach_div = priv->type_fan_tach_clock_division[type];
--
2.13.1.611.g7e3b11ae1-goog