From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-path: From: Patrick Venture To: venture@google.com, joel@jms.id.au, linux@roeck-us.net Cc: linux-hwmon@vger.kernel.org, emilyshaffer@google.com, peterh@google.com Subject: [PATCH 1/2 v4] hwmon: (aspeed-pwm-tacho) reduce fan_tach period Date: Sat, 24 Jun 2017 08:39:32 -0700 Message-Id: <20170624153932.8895-1-venture@google.com> List-ID: Reduce the fan_tach period such that the fan controller uses a shorter period to measure the rpm. The original period of 0x1000 was chosen as a conversative value from the reference implementation. Through experimentation on the quanta-q71l board, I was able to drive the number down which ultimately reduced the time the controller would use to determine the fan_tach. This value was recently tested and accepted downstream on the IBM Zaius board which uses the ast2500. Future work: It may be worthwhile as this is a tunable parameter to the system, to allow overriding it through the device tree. Testing: Tested on an ast2400 sitting on a quanta-q71l and ast2500 on power9. Signed-off-by: Patrick Venture --- v4: Added explanation for value. v3: Added missing change log v2: Updated commit message language --- drivers/hwmon/aspeed-pwm-tacho.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/hwmon/aspeed-pwm-tacho.c b/drivers/hwmon/aspeed-pwm-tacho.c index 86e2ea8287a7..b2ab5612d8a4 100644 --- a/drivers/hwmon/aspeed-pwm-tacho.c +++ b/drivers/hwmon/aspeed-pwm-tacho.c @@ -160,7 +160,7 @@ * 11: reserved. */ #define M_TACH_MODE 0x02 /* 10b */ -#define M_TACH_UNIT 0x1000 +#define M_TACH_UNIT 0x00c0 #define INIT_FAN_CTRL 0xFF struct aspeed_pwm_tacho_data { -- 2.13.1.611.g7e3b11ae1-goog