On Thu, 2013-10-17 at 00:51 -0500, Wang Dongsheng-B40534 wrote:

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

+static ssize_t show_pw20_wait_time(struct device *dev,
+				struct device_attribute *attr, char *buf) {
+	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;

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, 

Actually, tb_cycle will be undefined because you shifted a 32-bit value
(1) by more than 31 bits.  s/1/1ULL/

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).

Why can it not be increased?

-Scott