On Thu, 2013-10-17 at 22:02 -0500, Wang Dongsheng-B40534 wrote:

quoted

-----Original Message-----
From: Bhushan Bharat-R65777
Sent: Thursday, October 17, 2013 2:46 PM
To: Wang Dongsheng-B40534; Wood Scott-B07421
Cc: linuxppc-dev@lists.ozlabs.org
Subject: RE: [PATCH v5 4/4] powerpc/85xx: add sysfs for pw20 state and
altivec idle

quoted

quoted

quoted

-----Original Message-----
From: Wang Dongsheng-B40534
Sent: Thursday, October 17, 2013 11:22 AM
To: Bhushan Bharat-R65777; Wood Scott-B07421
Cc: linuxppc-dev@lists.ozlabs.org
Subject: RE: [PATCH v5 4/4] powerpc/85xx: add sysfs for pw20 state
and altivec idle

quoted

-----Original Message-----
From: Bhushan Bharat-R65777
Sent: Thursday, October 17, 2013 11:20 AM
To: Wang Dongsheng-B40534; Wood Scott-B07421
Cc: linuxppc-dev@lists.ozlabs.org
Subject: RE: [PATCH v5 4/4] powerpc/85xx: add sysfs for pw20
state and altivec idle

quoted

-----Original Message-----
From: Wang Dongsheng-B40534
Sent: Thursday, October 17, 2013 8:16 AM
To: Bhushan Bharat-R65777; Wood Scott-B07421
Cc: linuxppc-dev@lists.ozlabs.org
Subject: RE: [PATCH v5 4/4] powerpc/85xx: add sysfs for pw20
state and altivec idle

quoted

-----Original Message-----
From: Bhushan Bharat-R65777
Sent: Thursday, October 17, 2013 1:01 AM
To: Wang Dongsheng-B40534; Wood Scott-B07421
Cc: linuxppc-dev@lists.ozlabs.org
Subject: RE: [PATCH v5 4/4] powerpc/85xx: add sysfs for pw20
state and altivec idle

quoted

-----Original Message-----
From: Wang Dongsheng-B40534
Sent: Tuesday, October 15, 2013 2:51 PM
To: Wood Scott-B07421
Cc: Bhushan Bharat-R65777; linuxppc-dev@lists.ozlabs.org;
Wang

Dongsheng-B40534

quoted

Subject: [PATCH v5 4/4] powerpc/85xx: add sysfs for pw20
state and

altivec idle

quoted

From: Wang Dongsheng <redacted>

Add a sys interface to enable/diable pw20 state or altivec
idle, and

control the

quoted

wait entry time.

Enable/Disable interface:
0, disable. 1, enable.
/sys/devices/system/cpu/cpuX/pw20_state
/sys/devices/system/cpu/cpuX/altivec_idle

Set wait time interface:(Nanosecond)
/sys/devices/system/cpu/cpuX/pw20_wait_time
/sys/devices/system/cpu/cpuX/altivec_idle_wait_time
Example: Base on TBfreq is 41MHZ.
1~48(ns): TB[63]
49~97(ns): TB[62]
98~195(ns): TB[61]
196~390(ns): TB[60]
391~780(ns): TB[59]
781~1560(ns): TB[58]
...

Signed-off-by: Wang Dongsheng
[off-list ref]
---
*v5:
Change get_idle_ticks_bit function implementation.

*v4:
Move code from 85xx/common.c to kernel/sysfs.c.

Remove has_pw20_altivec_idle function.

Change wait "entry_bit" to wait time.

diff --git a/arch/powerpc/kernel/sysfs.c

b/arch/powerpc/kernel/sysfs.c

index

quoted

27a90b9..10d1128 100644

--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c

@@ -85,6 +85,284 @@ __setup("smt-snooze-delay=",

setup_smt_snooze_delay);

quoted

 #endif /* CONFIG_PPC64 */

+#ifdef CONFIG_FSL_SOC
+#define MAX_BIT				63
+
+static u64 pw20_wt;
+static u64 altivec_idle_wt;
+
+static unsigned int get_idle_ticks_bit(u64 ns) {
+	u64 cycle;
+
+	if (ns >= 10000)
+		cycle = div_u64(ns + 500, 1000) *

tb_ticks_per_usec;

quoted

quoted

quoted

quoted

quoted

quoted

quoted

+	else
+		cycle = div_u64(ns * tb_ticks_per_usec, 1000);
+
+	if (!cycle)
+		return 0;
+
+	return ilog2(cycle);
+}
+
+static void do_show_pwrmgtcr0(void *val) {
+	u32 *value = val;
+
+	*value = mfspr(SPRN_PWRMGTCR0); }
+
+static ssize_t show_pw20_state(struct device *dev,
+				struct device_attribute *attr, char

*buf) {

quoted

quoted

quoted

quoted

quoted

quoted

quoted

+	u32 value;
+	unsigned int cpu = dev->id;
+
+	smp_call_function_single(cpu, do_show_pwrmgtcr0, &value,
+1);
+
+	value &= PWRMGTCR0_PW20_WAIT;
+
+	return sprintf(buf, "%u\n", value ? 1 : 0); }
+
+static void do_store_pw20_state(void *val) {
+	u32 *value = val;
+	u32 pw20_state;
+
+	pw20_state = mfspr(SPRN_PWRMGTCR0);
+
+	if (*value)
+		pw20_state |= PWRMGTCR0_PW20_WAIT;
+	else
+		pw20_state &= ~PWRMGTCR0_PW20_WAIT;
+
+	mtspr(SPRN_PWRMGTCR0, pw20_state); }
+
+static ssize_t store_pw20_state(struct device *dev,
+				struct device_attribute *attr,
+				const char *buf, size_t count) {
+	u32 value;
+	unsigned int cpu = dev->id;
+
+	if (kstrtou32(buf, 0, &value))
+		return -EINVAL;
+
+	if (value > 1)
+		return -EINVAL;
+
+	smp_call_function_single(cpu, do_store_pw20_state,
+&value, 1);
+
+	return count;
+}
+
+static ssize_t show_pw20_wait_time(struct device *dev,
+				struct device_attribute *attr, char

*buf) {

quoted

quoted

quoted

quoted

quoted

quoted

quoted

+	u32 value;
+	u64 tb_cycle;
+	s64 time;
+
+	unsigned int cpu = dev->id;
+
+	if (!pw20_wt) {
+		smp_call_function_single(cpu, do_show_pwrmgtcr0,
+&value,

1);

quoted

quoted

quoted

+		value = (value & PWRMGTCR0_PW20_ENT) >>
+					PWRMGTCR0_PW20_ENT_SHIFT;
+
+		tb_cycle = (1 << (MAX_BIT - value)) * 2;

Is value = 0 and value = 1 legal? These will make tb_cycle =
0,

quoted

+		time = div_u64(tb_cycle * 1000, tb_ticks_per_usec)

- 1;

quoted

quoted

quoted

quoted

quoted

quoted

And time = -1;

Please look at the end of the function, :)

"return sprintf(buf, "%llu\n", time > 0 ? time : 0);"

I know you return 0 if value = 0/1, my question was that, is
this correct as per specification?

Ahh, also for "value" upto 7 you will return 0, no?

If value = 0, MAX_BIT - value = 63 tb_cycle = 0xffffffff_ffffffff,
tb_cycle * 1000 will overflow, but this situation is not possible.
Because if the "value = 0" means this feature will be "disable".
Now The default wait bit is 50(MAX_BIT - value, value = 13), the
PW20/Altivec Idle wait entry time is about 1ms, this time is very
long for wait idle time, and it's cannot be increased(means
(MAX_BIT
- value)

cannot greater than 50).

What you said is not obvious from code and so at least write a
comment that value will be always >= 13 or value will never be less
than < 8 and below calculation will not overflow. may be error out
if value is less than 8.

The "value" less than 10, this will overflow.
There is not error, The code I knew it could not be less than 10,
that's why I use the following code. :)

I am sorry to persist but this is not about what you know, this is about
how code is read and code does not say what you know, so add a comment at
least and error out/warn when "value" is less than a certain number.

Sorry for the late to response the mail. If it caused confusion, we can add a comment.

How about the following comment?
/*
 * If the "value" less than 10, this will overflow.
 * From benchmark test, the default wait bit will not be set less than 10bit.
 * Because 10 bit corresponds to the wait entry time is 439375573401999609(ns),
 * for wait-entry-idle time this value looks too long, and we cannot use those
 * "long" time as a default wait-entry time. So overflow could not have happened
 * and we use this calculation method to get wait-entry-idle time.
 */

If there's to be a limit on the times we accept, make it explicit.
Check for it before doing any conversions, and return an error if
userspace tries to set it.

-Scott