diff mbox series

[2/2] powerpc/pseries: Set CPU_FTR_DBELL according to ibm,pi-features

Message ID 20240207035220.339726-2-npiggin@gmail.com (mailing list archive)
State Accepted
Commit 6e9de2054eb417d6e05561b19c825c29b424b475
Headers show
Series [1/2] powerpc/pseries: Add a clear modifier to ibm,pa/pi-features parser | expand

Commit Message

Nicholas Piggin Feb. 7, 2024, 3:52 a.m. UTC 
PAPR will define a new ibm,pi-features bit which says that doorbells
should not be used even on architectures where they exist. This could be
because they are emulated and slower than using the interrupt controller
directly for IPIs.

Wire this bit into the pi-features parser to clear CPU_FTR_DBELL, and
ensure CPU_FTR_DBELL is not in CPU_FTRS_ALWAYS.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/include/asm/cputable.h | 11 ++++++-----
 arch/powerpc/kernel/prom.c          |  1 +
 2 files changed, 7 insertions(+), 5 deletions(-)

Comments

Vaibhav Jain Feb. 7, 2024, 5:16 p.m. UTC | #1 
Nicholas Piggin <npiggin@gmail.com> writes:

> PAPR will define a new ibm,pi-features bit which says that doorbells
> should not be used even on architectures where they exist. This could be
> because they are emulated and slower than using the interrupt controller
> directly for IPIs.
>
> Wire this bit into the pi-features parser to clear CPU_FTR_DBELL, and
> ensure CPU_FTR_DBELL is not in CPU_FTRS_ALWAYS.
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---

Tested this patch on a PP64-LE lpar with the patch[1] and seeing the
relevant pi-feature bit CPU_FTR_DBELL in `cur_cpu_spec->cpu_features`
getting cleared.


[1]
https://lore.kernel.org/all/20240207035220.339726-1-npiggin@gmail.com

Hence,
Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com>
diff mbox series

Patch

diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index 8765d5158324..48471ca388dd 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -542,19 +542,20 @@  enum {
 #define CPU_FTRS_DT_CPU_BASE	(~0ul)
 #endif
 
+/* pseries may disable DBELL with ibm,pi-features */
 #ifdef CONFIG_CPU_LITTLE_ENDIAN
 #define CPU_FTRS_ALWAYS \
-	    (CPU_FTRS_POSSIBLE & ~CPU_FTR_HVMODE & CPU_FTRS_POWER7 & \
-	     CPU_FTRS_POWER8E & CPU_FTRS_POWER8 & CPU_FTRS_POWER9 & \
-	     CPU_FTRS_POWER9_DD2_1 & CPU_FTRS_POWER9_DD2_2 & \
+	    (CPU_FTRS_POSSIBLE & ~CPU_FTR_HVMODE & ~CPU_FTR_DBELL & \
+	     CPU_FTRS_POWER7 & CPU_FTRS_POWER8E & CPU_FTRS_POWER8 & \
+	     CPU_FTRS_POWER9 & CPU_FTRS_POWER9_DD2_1 & CPU_FTRS_POWER9_DD2_2 & \
 	     CPU_FTRS_POWER10 & CPU_FTRS_DT_CPU_BASE)
 #else
 #define CPU_FTRS_ALWAYS		\
 	    (CPU_FTRS_PPC970 & CPU_FTRS_POWER5 & \
 	     CPU_FTRS_POWER6 & CPU_FTRS_POWER7 & CPU_FTRS_CELL & \
 	     CPU_FTRS_PA6T & CPU_FTRS_POWER8 & CPU_FTRS_POWER8E & \
-	     ~CPU_FTR_HVMODE & CPU_FTRS_POSSIBLE & CPU_FTRS_POWER9 & \
-	     CPU_FTRS_POWER9_DD2_1 & CPU_FTRS_POWER9_DD2_2 & \
+	     ~CPU_FTR_HVMODE & ~CPU_FTR_DBELL & CPU_FTRS_POSSIBLE & \
+	     CPU_FTRS_POWER9 & CPU_FTRS_POWER9_DD2_1 & CPU_FTRS_POWER9_DD2_2 & \
 	     CPU_FTRS_POWER10 & CPU_FTRS_DT_CPU_BASE)
 #endif /* CONFIG_CPU_LITTLE_ENDIAN */
 #endif
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 62f4a0229fae..e3e8fe70475f 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -196,6 +196,7 @@  static struct ibm_feature ibm_pa_features[] __initdata = {
  */
 static struct ibm_feature ibm_pi_features[] __initdata = {
 	{ .pabyte = 0, .pabit = 3, .mmu_features  = MMU_FTR_NX_DSI },
+	{ .pabyte = 0, .pabit = 4, .cpu_features  = CPU_FTR_DBELL, .clear = 1 },
 };
 
 static void __init scan_features(unsigned long node, const unsigned char *ftrs,