Re: [PATCH v3] powerpc: Add an inline function to update POWER8 HID0

[Shreyas B Prabhu]

On 08/05/2015 12:38 PM, Gautham R. Shenoy wrote:
 Section 3.7 of Version 1.2 of the Power8 Processor User's Manual
 prescribes that updates to HID0 be preceded by a SYNC instruction and
 followed by an ISYNC instruction (Page 91).
 
 Create an inline function name update_power8_hid0() which follows this
 recipe and invoke it from the static split core path.
 
 Signed-off-by: Gautham R. Shenoy e...@linux.vnet.ibm.com

Reviewed-by: Shreyas B. Prabhu shre...@linux.vnet.ibm.com

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Re: [PATCH v3] powerpc: Add an inline function to update POWER8 HID0

[Sam Bobroff]

On Wed, Aug 05, 2015 at 12:38:31PM +0530, Gautham R. Shenoy wrote:
 Section 3.7 of Version 1.2 of the Power8 Processor User's Manual
 prescribes that updates to HID0 be preceded by a SYNC instruction and
 followed by an ISYNC instruction (Page 91).
 
 Create an inline function name update_power8_hid0() which follows this
 recipe and invoke it from the static split core path.
 
 Signed-off-by: Gautham R. Shenoy e...@linux.vnet.ibm.com

Hi Gautham,

I've tested this on a Power 8 machine and verified that it is able to change
split modes and that when doing so the new code is used.

Reviewed-by: Sam Bobroff sam.bobr...@au1.ibm.com
Tested-by: Sam Bobroff sam.bobr...@au1.ibm.com

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[PATCH v3] powerpc: Add an inline function to update POWER8 HID0

[Gautham R. Shenoy]

Section 3.7 of Version 1.2 of the Power8 Processor User's Manual
prescribes that updates to HID0 be preceded by a SYNC instruction and
followed by an ISYNC instruction (Page 91).

Create an inline function name update_power8_hid0() which follows this
recipe and invoke it from the static split core path.

Signed-off-by: Gautham R. Shenoy e...@linux.vnet.ibm.com
---
[v1 -- v2: Moved defn of update_hid0 to reg.h from kvm_ppc.h]
[v2 -- v3: Renamed to update_power8_hid0 and used asm volatile]

 arch/powerpc/include/asm/reg.h   | 9 +
 arch/powerpc/platforms/powernv/subcore.c | 4 ++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index af56b5c..1245d99 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -1281,6 +1281,15 @@ struct pt_regs;
 
 extern void ppc_save_regs(struct pt_regs *regs);
 
+static inline void update_power8_hid0(unsigned long hid0)
+{
+   /*
+*  The HID0 update on Power8 should at the very least be
+*  preceded by a a SYNC instruction followed by an ISYNC
+*  instruction
+*/
+   asm volatile(sync; mtspr %0,%1; isync:: i(SPRN_HID0), r(hid0));
+}
 #endif /* __ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_REG_H */
diff --git a/arch/powerpc/platforms/powernv/subcore.c 
b/arch/powerpc/platforms/powernv/subcore.c
index f60f80a..503a73f 100644
--- a/arch/powerpc/platforms/powernv/subcore.c
+++ b/arch/powerpc/platforms/powernv/subcore.c
@@ -190,7 +190,7 @@ static void unsplit_core(void)
 
hid0 = mfspr(SPRN_HID0);
hid0 = ~HID0_POWER8_DYNLPARDIS;
-   mtspr(SPRN_HID0, hid0);
+   update_power8_hid0(hid0);
update_hid_in_slw(hid0);
 
while (mfspr(SPRN_HID0)  mask)
@@ -227,7 +227,7 @@ static void split_core(int new_mode)
/* Write new mode */
hid0  = mfspr(SPRN_HID0);
hid0 |= HID0_POWER8_DYNLPARDIS | split_parms[i].value;
-   mtspr(SPRN_HID0, hid0);
+   update_power8_hid0(hid0);
update_hid_in_slw(hid0);
 
/* Wait for it to happen */
-- 
1.9.3

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