[linux-yocto] [PATCH 09/22] valleyisland-io: improve the base calculation in pwm

[boon.leong.ong at intel.com]

From: Ong Boon Leong <boon.leong.ong at intel.com>

This improves the accuracy of base_unit calculation
so that the resulting PWM frequency will be more optimal.

The change in the patch is meant for Intel BayTrail only
because pwm-lpss.c is only used for this platform.

Signed-off-by: Ong Boon Leong <boon.leong.ong at intel.com>
---
 .../0007-pwm-lpss-Fix-base_unit-calculation.patch  |   91 ++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 meta/cfg/kernel-cache/features/valleyisland-io/0007-pwm-lpss-Fix-base_unit-calculation.patch

diff --git a/meta/cfg/kernel-cache/features/valleyisland-io/0007-pwm-lpss-Fix-base_unit-calculation.patch b/meta/cfg/kernel-cache/features/valleyisland-io/0007-pwm-lpss-Fix-base_unit-calculation.patch
new file mode 100644
index 0000000..73cc07d
--- /dev/null
+++ b/meta/cfg/kernel-cache/features/valleyisland-io/0007-pwm-lpss-Fix-base_unit-calculation.patch
@@ -0,0 +1,91 @@
+From f0f4356d0823e08c6803283e35a7e49a2197e20e Mon Sep 17 00:00:00 2001
+From: Chew, Chiau Ee <chiau.ee.chew at intel.com>
+Date: Mon, 13 Jan 2014 19:10:42 +0800
+Subject: [PATCH 07/17] pwm: lpss: Improve base_unit calculation
+
+This improves the accuracy of base_unit calculation
+so that the resulting PWM frequency will be more
+optimal.
+
+As pwm-lpss.c is only meant Intel BayTrail pwm,
+the changes below do not impact other platform.
+
+Signed-off-by: Chew, Kean Ho <kean.ho.chew at intel.com>
+Signed-off-by: Chew, Chiau Ee <chiau.ee.chew at intel.com>
+---
+ drivers/pwm/pwm-lpss.c |   25 ++++++++++---------------
+ drivers/pwm/pwm-lpss.h |   14 ++++++++------
+ 2 files changed, 18 insertions(+), 21 deletions(-)
+
+diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
+index eeed096..7fae747 100644
+--- a/drivers/pwm/pwm-lpss.c
++++ b/drivers/pwm/pwm-lpss.c
+@@ -35,32 +35,27 @@ static int pwm_lpss_config(struct pwm_chip *chip, struct pwm_device *pwm,
+ 	int duty_ns, int period_ns)
+ {
+ 	struct pwm_lpss_chip *lpwm = to_lpwm(chip);
+-	u8 base_unit_hi, base_unit_lo, on_time_div;
++	u8 on_time_div;
+ 	unsigned long c = clk_get_rate(lpwm->clk);
+-	unsigned long hz, cycle_cnt;
++	unsigned long long base_unit, hz = 1000000000UL;
+ 	u32 ctrl;
+
+-	hz = 1000000000UL / period_ns;
++	do_div(hz, period_ns);
+
+-	/*
+-	 * There is no duty cycle resolution if base_unit value is higher
+-	 * than 128.
+-	 */
+-	base_unit_hi = (hz * 256) / c;
+-	if (base_unit_hi > 128)
++	/* The equation is: base_unit = ((hz / c) * 65536) + correction */
++	base_unit = hz * 65536;
++	do_div(base_unit, c);
++	base_unit += PWM_DIVISION_CORRECTION;
++	if (base_unit > PWM_LIMIT)
+ 		return -EINVAL;
+
+-	base_unit_lo = (hz * 65536) / c;
+-	cycle_cnt = base_unit_hi ? 256 / base_unit_hi : 256;
+-
+ 	if (duty_ns <= 0)
+ 		duty_ns = 1;
+-
+-	on_time_div = cycle_cnt / (period_ns / duty_ns);
++	on_time_div = 255 - (255 * duty_ns / period_ns);
+
+ 	ctrl = readl(lpwm->regs + PWM);
+ 	ctrl &= ~(PWM_BASE_UNIT_MASK | PWM_ON_TIME_DIV_MASK);
+-	ctrl |= (base_unit_hi | base_unit_lo) << PWM_BASE_UNIT_SHIFT;
++	ctrl |= (u16) base_unit << PWM_BASE_UNIT_SHIFT;
+ 	ctrl |= on_time_div;
+ 	/* request PWM to update on next cycle */
+ 	ctrl |= PWM_SW_UPDATE;
+diff --git a/drivers/pwm/pwm-lpss.h b/drivers/pwm/pwm-lpss.h
+index d1705e5..a9f2307 100644
+--- a/drivers/pwm/pwm-lpss.h
++++ b/drivers/pwm/pwm-lpss.h
+@@ -1,9 +1,11 @@
+-#define PWM			0x00000000
+-#define PWM_ENABLE		BIT(31)
+-#define PWM_SW_UPDATE		BIT(30)
+-#define PWM_BASE_UNIT_SHIFT	8
+-#define PWM_BASE_UNIT_MASK	0x00ffff00
+-#define PWM_ON_TIME_DIV_MASK	0x000000ff
++#define PWM				0x00000000
++#define PWM_ENABLE			BIT(31)
++#define PWM_SW_UPDATE			BIT(30)
++#define PWM_BASE_UNIT_SHIFT		8
++#define PWM_BASE_UNIT_MASK		0x00ffff00
++#define PWM_ON_TIME_DIV_MASK		0x000000ff
++#define PWM_DIVISION_CORRECTION		0x2
++#define PWM_LIMIT			(0x8000 + PWM_DIVISION_CORRECTION)
+
+ struct pwm_lpss_chip {
+ 	struct pwm_chip chip;
+--
+1.7.4.4
+
-- 
1.7.10.4