Re: [PATCH v4 05/10] powerpc/dt_cpu_ftrs: Add feature for 2nd DAWR
From: Ravi Bangoria
Date: Tue Jul 21 2020 - 10:17:45 EST
On 7/21/20 7:37 PM, Michael Ellerman wrote:
Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx> writes:
On 7/21/20 4:59 PM, Michael Ellerman wrote:
Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx> writes:
On 7/17/20 11:14 AM, Jordan Niethe wrote:
On Fri, Jul 17, 2020 at 2:10 PM Ravi Bangoria
<ravi.bangoria@xxxxxxxxxxxxx> wrote:
Add new device-tree feature for 2nd DAWR. If this feature is present,
2nd DAWR is supported, otherwise not.
Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxx>
---
arch/powerpc/include/asm/cputable.h | 7 +++++--
arch/powerpc/kernel/dt_cpu_ftrs.c | 7 +++++++
2 files changed, 12 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index e506d429b1af..3445c86e1f6f 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -214,6 +214,7 @@ static inline void cpu_feature_keys_init(void) { }
#define CPU_FTR_P9_TLBIE_ERAT_BUG LONG_ASM_CONST(0x0001000000000000)
#define CPU_FTR_P9_RADIX_PREFETCH_BUG LONG_ASM_CONST(0x0002000000000000)
#define CPU_FTR_ARCH_31 LONG_ASM_CONST(0x0004000000000000)
+#define CPU_FTR_DAWR1 LONG_ASM_CONST(0x0008000000000000)
#ifndef __ASSEMBLY__
@@ -497,14 +498,16 @@ static inline void cpu_feature_keys_init(void) { }
#define CPU_FTRS_POSSIBLE \
(CPU_FTRS_POWER7 | CPU_FTRS_POWER8E | CPU_FTRS_POWER8 | \
CPU_FTR_ALTIVEC_COMP | CPU_FTR_VSX_COMP | CPU_FTRS_POWER9 | \
- CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10)
+ CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10 | \
+ CPU_FTR_DAWR1)
#else
#define CPU_FTRS_POSSIBLE \
(CPU_FTRS_PPC970 | CPU_FTRS_POWER5 | \
CPU_FTRS_POWER6 | CPU_FTRS_POWER7 | CPU_FTRS_POWER8E | \
CPU_FTRS_POWER8 | CPU_FTRS_CELL | CPU_FTRS_PA6T | \
CPU_FTR_VSX_COMP | CPU_FTR_ALTIVEC_COMP | CPU_FTRS_POWER9 | \
- CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10)
+ CPU_FTRS_POWER9_DD2_1 | CPU_FTRS_POWER9_DD2_2 | CPU_FTRS_POWER10 | \
+ CPU_FTR_DAWR1)
Instead of putting CPU_FTR_DAWR1 into CPU_FTRS_POSSIBLE should it go
into CPU_FTRS_POWER10?
Then it will be picked up by CPU_FTRS_POSSIBLE.
I remember a discussion about this with Mikey and we decided to do it
this way. Obviously, the purpose is to make CPU_FTR_DAWR1 independent of
CPU_FTRS_POWER10 because DAWR1 is an optional feature in p10. I fear
including CPU_FTR_DAWR1 in CPU_FTRS_POWER10 can make it forcefully enabled
even when device-tree property is not present or pa-feature bit it not set,
because we do:
{ /* 3.1-compliant processor, i.e. Power10 "architected" mode */
.pvr_mask = 0xffffffff,
.pvr_value = 0x0f000006,
.cpu_name = "POWER10 (architected)",
.cpu_features = CPU_FTRS_POWER10,
The pa-features logic will turn it off if the feature bit is not set.
So you should be able to put it in CPU_FTRS_POWER10.
See for example CPU_FTR_NOEXECUTE.
Ah ok. scan_features() clears the feature if the bit is not set in
pa-features. So it should work find for powervm. I'll verify the same
thing happens in case of baremetal where we use cpu-features not
pa-features. If it works in baremetal as well, will put it in
CPU_FTRS_POWER10.
When we use DT CPU features we don't use CPU_FTRS_POWER10 at all.
We construct a cpu_spec from scratch with just the base set of features:
static struct cpu_spec __initdata base_cpu_spec = {
.cpu_name = NULL,
.cpu_features = CPU_FTRS_DT_CPU_BASE,
And then individual features are enabled via the device tree flags.
Ah good. I was under a wrong impression that we use cpu_specs[] for all
the cases. Thanks mpe for explaining in detail :)
Ravi