[PATCH RESEND v4 0/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO

[PATCH RESEND v4 0/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO

[Jisheng Zhang]

Previously, we use alternative mechanism to dynamically patch
the CMO operations for THEAD C906/C910 during boot for performance
reason. But as pointed out by Arnd, "there is already a significant
cost in accessing the invalidated cache lines afterwards, which is
likely going to be much higher than the cost of an indirect branch".
And indeed, there's no performance difference with GMAC and EMMC per
my test on Sipeed Lichee Pi 4A board.

Use riscv_nonstd_cache_ops for THEAD C906/C910 CMO to simplify
the alternative code, and to acchieve Arnd's goal -- "I think
moving the THEAD ops at the same level as all nonstandard operations
makes sense, but I'd still leave CMO as an explicit fast path that
avoids the indirect branch. This seems like the right thing to do both
for readability and for platforms on which the indirect branch has a
noticeable overhead."

To make bisect easy, I use two patches here: patch1 does the conversion
which just mimics current CMO behavior via. riscv_nonstd_cache_ops, I
assume no functionalities changes. patch2 uses T-HEAD PA based CMO
instructions so that we don't need to covert PA to VA.

since v4:
  - rebase on 6.7rc1

since v3:
  - collect Reviewed-by tag

since v2:
  - collect Reviewed-by tag (but missed them in fact)
  - fix typo

since v1:
  - collect Tested-by tag
  - add patch2 to use T-HEAD PA based CMO instructions.

Jisheng Zhang (2):
  riscv: errata: thead: use riscv_nonstd_cache_ops for CMO
  riscv: errata: thead: use pa based instructions for CMO

 arch/riscv/Kconfig.errata            |  1 +
 arch/riscv/errata/thead/errata.c     | 69 +++++++++++++++++++++++++++-
 arch/riscv/include/asm/errata_list.h | 50 +++-----------------
 3 files changed, 74 insertions(+), 46 deletions(-)

-- 
2.40.0


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH RESEND v4 1/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO

[Jisheng Zhang]

Previously, we use alternative mechanism to dynamically patch
the CMO operations for THEAD C906/C910 during boot for performance
reason. But as pointed out by Arnd, "there is already a significant
cost in accessing the invalidated cache lines afterwards, which is
likely going to be much higher than the cost of an indirect branch".
And indeed, there's no performance difference with GMAC and EMMC per
my test on Sipeed Lichee Pi 4A board.

Use riscv_nonstd_cache_ops for THEAD C906/C910 CMO to simplify
the alternative code, and to acchieve Arnd's goal -- "I think
moving the THEAD ops at the same level as all nonstandard operations
makes sense, but I'd still leave CMO as an explicit fast path that
avoids the indirect branch. This seems like the right thing to do both
for readability and for platforms on which the indirect branch has a
noticeable overhead."

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Tested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
---
 arch/riscv/Kconfig.errata            |  1 +
 arch/riscv/errata/thead/errata.c     | 75 +++++++++++++++++++++++++++-
 arch/riscv/include/asm/errata_list.h | 50 +++----------------
 3 files changed, 80 insertions(+), 46 deletions(-)

diff --git a/arch/riscv/Kconfig.errata b/arch/riscv/Kconfig.errata
index e2c731cfed8c..dedb8b238e73 100644
--- a/arch/riscv/Kconfig.errata
+++ b/arch/riscv/Kconfig.errata
@@ -79,6 +79,7 @@ config ERRATA_THEAD_CMO
 	depends on ERRATA_THEAD && MMU
 	select DMA_DIRECT_REMAP
 	select RISCV_DMA_NONCOHERENT
+	select RISCV_NONSTANDARD_CACHE_OPS
 	default y
 	help
 	  This will apply the cache management errata to handle the
diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
index 0554ed4bf087..c07d957b1468 100644
--- a/arch/riscv/errata/thead/errata.c
+++ b/arch/riscv/errata/thead/errata.c
@@ -12,8 +12,10 @@
 #include <asm/alternative.h>
 #include <asm/cacheflush.h>
 #include <asm/cpufeature.h>
+#include <asm/dma-noncoherent.h>
 #include <asm/errata_list.h>
 #include <asm/hwprobe.h>
+#include <asm/io.h>
 #include <asm/patch.h>
 #include <asm/vendorid_list.h>
 
@@ -33,6 +35,75 @@ static bool errata_probe_pbmt(unsigned int stage,
 	return false;
 }
 
+/*
+ * th.dcache.ipa rs1 (invalidate, physical address)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000001    01010      rs1       000      00000  0001011
+ * th.dcache.iva rs1 (invalidate, virtual address)
+ *   0000001    00110      rs1       000      00000  0001011
+ *
+ * th.dcache.cpa rs1 (clean, physical address)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000001    01001      rs1       000      00000  0001011
+ * th.dcache.cva rs1 (clean, virtual address)
+ *   0000001    00101      rs1       000      00000  0001011
+ *
+ * th.dcache.cipa rs1 (clean then invalidate, physical address)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000001    01011      rs1       000      00000  0001011
+ * th.dcache.civa rs1 (clean then invalidate, virtual address)
+ *   0000001    00111      rs1       000      00000  0001011
+ *
+ * th.sync.s (make sure all cache operations finished)
+ * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
+ *   0000000    11001     00000      000      00000  0001011
+ */
+#define THEAD_INVAL_A0	".long 0x0265000b"
+#define THEAD_CLEAN_A0	".long 0x0255000b"
+#define THEAD_FLUSH_A0	".long 0x0275000b"
+#define THEAD_SYNC_S	".long 0x0190000b"
+
+#define THEAD_CMO_OP(_op, _start, _size, _cachesize)			\
+asm volatile("mv a0, %1\n\t"						\
+	     "j 2f\n\t"							\
+	     "3:\n\t"							\
+	     THEAD_##_op##_A0 "\n\t"					\
+	     "add a0, a0, %0\n\t"					\
+	     "2:\n\t"							\
+	     "bltu a0, %2, 3b\n\t"					\
+	     THEAD_SYNC_S						\
+	     : : "r"(_cachesize),					\
+		 "r"((unsigned long)(_start) & ~((_cachesize) - 1UL)),	\
+		 "r"((unsigned long)(_start) + (_size))			\
+	     : "a0")
+
+static void thead_errata_cache_inv(phys_addr_t paddr, size_t size)
+{
+	void *vaddr = phys_to_virt(paddr);
+
+	THEAD_CMO_OP(INVAL, vaddr, size, riscv_cbom_block_size);
+}
+
+static void thead_errata_cache_wback(phys_addr_t paddr, size_t size)
+{
+	void *vaddr = phys_to_virt(paddr);
+
+	THEAD_CMO_OP(CLEAN, vaddr, size, riscv_cbom_block_size);
+}
+
+static void thead_errata_cache_wback_inv(phys_addr_t paddr, size_t size)
+{
+	void *vaddr = phys_to_virt(paddr);
+
+	THEAD_CMO_OP(FLUSH, vaddr, size, riscv_cbom_block_size);
+}
+
+static const struct riscv_nonstd_cache_ops thead_errata_cmo_ops = {
+	.wback = &thead_errata_cache_wback,
+	.inv = &thead_errata_cache_inv,
+	.wback_inv = &thead_errata_cache_wback_inv,
+};
+
 static bool errata_probe_cmo(unsigned int stage,
 			     unsigned long arch_id, unsigned long impid)
 {
@@ -48,6 +119,7 @@ static bool errata_probe_cmo(unsigned int stage,
 	if (stage == RISCV_ALTERNATIVES_BOOT) {
 		riscv_cbom_block_size = L1_CACHE_BYTES;
 		riscv_noncoherent_supported();
+		riscv_noncoherent_register_cache_ops(&thead_errata_cmo_ops);
 	}
 
 	return true;
@@ -77,8 +149,7 @@ static u32 thead_errata_probe(unsigned int stage,
 	if (errata_probe_pbmt(stage, archid, impid))
 		cpu_req_errata |= BIT(ERRATA_THEAD_PBMT);
 
-	if (errata_probe_cmo(stage, archid, impid))
-		cpu_req_errata |= BIT(ERRATA_THEAD_CMO);
+	errata_probe_cmo(stage, archid, impid);
 
 	if (errata_probe_pmu(stage, archid, impid))
 		cpu_req_errata |= BIT(ERRATA_THEAD_PMU);
diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
index 83ed25e43553..ea33288f8a25 100644
--- a/arch/riscv/include/asm/errata_list.h
+++ b/arch/riscv/include/asm/errata_list.h
@@ -24,9 +24,8 @@
 
 #ifdef CONFIG_ERRATA_THEAD
 #define	ERRATA_THEAD_PBMT 0
-#define	ERRATA_THEAD_CMO 1
-#define	ERRATA_THEAD_PMU 2
-#define	ERRATA_THEAD_NUMBER 3
+#define	ERRATA_THEAD_PMU 1
+#define	ERRATA_THEAD_NUMBER 2
 #endif
 
 #ifdef __ASSEMBLY__
@@ -94,54 +93,17 @@ asm volatile(ALTERNATIVE(						\
 #define ALT_THEAD_PMA(_val)
 #endif
 
-/*
- * th.dcache.ipa rs1 (invalidate, physical address)
- * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
- *   0000001    01010      rs1       000      00000  0001011
- * th.dache.iva rs1 (invalida, virtual address)
- *   0000001    00110      rs1       000      00000  0001011
- *
- * th.dcache.cpa rs1 (clean, physical address)
- * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
- *   0000001    01001      rs1       000      00000  0001011
- * th.dcache.cva rs1 (clean, virtual address)
- *   0000001    00101      rs1       000      00000  0001011
- *
- * th.dcache.cipa rs1 (clean then invalidate, physical address)
- * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
- *   0000001    01011      rs1       000      00000  0001011
- * th.dcache.civa rs1 (... virtual address)
- *   0000001    00111      rs1       000      00000  0001011
- *
- * th.sync.s (make sure all cache operations finished)
- * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
- *   0000000    11001     00000      000      00000  0001011
- */
-#define THEAD_INVAL_A0	".long 0x0265000b"
-#define THEAD_CLEAN_A0	".long 0x0255000b"
-#define THEAD_FLUSH_A0	".long 0x0275000b"
-#define THEAD_SYNC_S	".long 0x0190000b"
-
 #define ALT_CMO_OP(_op, _start, _size, _cachesize)			\
-asm volatile(ALTERNATIVE_2(						\
-	__nops(6),							\
+asm volatile(ALTERNATIVE(						\
+	__nops(5),							\
 	"mv a0, %1\n\t"							\
 	"j 2f\n\t"							\
 	"3:\n\t"							\
 	CBO_##_op(a0)							\
 	"add a0, a0, %0\n\t"						\
 	"2:\n\t"							\
-	"bltu a0, %2, 3b\n\t"						\
-	"nop", 0, RISCV_ISA_EXT_ZICBOM, CONFIG_RISCV_ISA_ZICBOM,	\
-	"mv a0, %1\n\t"							\
-	"j 2f\n\t"							\
-	"3:\n\t"							\
-	THEAD_##_op##_A0 "\n\t"						\
-	"add a0, a0, %0\n\t"						\
-	"2:\n\t"							\
-	"bltu a0, %2, 3b\n\t"						\
-	THEAD_SYNC_S, THEAD_VENDOR_ID,					\
-			ERRATA_THEAD_CMO, CONFIG_ERRATA_THEAD_CMO)	\
+	"bltu a0, %2, 3b\n\t",						\
+	0, RISCV_ISA_EXT_ZICBOM, CONFIG_RISCV_ISA_ZICBOM)		\
 	: : "r"(_cachesize),						\
 	    "r"((unsigned long)(_start) & ~((_cachesize) - 1UL)),	\
 	    "r"((unsigned long)(_start) + (_size))			\
-- 
2.40.0


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

[PATCH RESEND v4 2/2] riscv: errata: thead: use pa based instructions for CMO

[Jisheng Zhang]

T-HEAD CPUs such as C906/C910/C920 support phy address based CMO, use
them so that we don't need to convert to virt address.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Guo Ren <guoren@kernel.org>
---
 arch/riscv/errata/thead/errata.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
index c07d957b1468..b1c410bbc1ae 100644
--- a/arch/riscv/errata/thead/errata.c
+++ b/arch/riscv/errata/thead/errata.c
@@ -58,9 +58,9 @@ static bool errata_probe_pbmt(unsigned int stage,
  * | 31 - 25 | 24 - 20 | 19 - 15 | 14 - 12 | 11 - 7 | 6 - 0 |
  *   0000000    11001     00000      000      00000  0001011
  */
-#define THEAD_INVAL_A0	".long 0x0265000b"
-#define THEAD_CLEAN_A0	".long 0x0255000b"
-#define THEAD_FLUSH_A0	".long 0x0275000b"
+#define THEAD_INVAL_A0	".long 0x02a5000b"
+#define THEAD_CLEAN_A0	".long 0x0295000b"
+#define THEAD_FLUSH_A0	".long 0x02b5000b"
 #define THEAD_SYNC_S	".long 0x0190000b"
 
 #define THEAD_CMO_OP(_op, _start, _size, _cachesize)			\
@@ -79,23 +79,17 @@ asm volatile("mv a0, %1\n\t"						\
 
 static void thead_errata_cache_inv(phys_addr_t paddr, size_t size)
 {
-	void *vaddr = phys_to_virt(paddr);
-
-	THEAD_CMO_OP(INVAL, vaddr, size, riscv_cbom_block_size);
+	THEAD_CMO_OP(INVAL, paddr, size, riscv_cbom_block_size);
 }
 
 static void thead_errata_cache_wback(phys_addr_t paddr, size_t size)
 {
-	void *vaddr = phys_to_virt(paddr);
-
-	THEAD_CMO_OP(CLEAN, vaddr, size, riscv_cbom_block_size);
+	THEAD_CMO_OP(CLEAN, paddr, size, riscv_cbom_block_size);
 }
 
 static void thead_errata_cache_wback_inv(phys_addr_t paddr, size_t size)
 {
-	void *vaddr = phys_to_virt(paddr);
-
-	THEAD_CMO_OP(FLUSH, vaddr, size, riscv_cbom_block_size);
+	THEAD_CMO_OP(FLUSH, paddr, size, riscv_cbom_block_size);
 }
 
 static const struct riscv_nonstd_cache_ops thead_errata_cmo_ops = {
-- 
2.40.0


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH RESEND v4 0/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO

[patchwork-bot+linux-riscv]

Hello:

This series was applied to riscv/linux.git (for-next)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Tue, 14 Nov 2023 22:33:36 +0800 you wrote:
> Previously, we use alternative mechanism to dynamically patch
> the CMO operations for THEAD C906/C910 during boot for performance
> reason. But as pointed out by Arnd, "there is already a significant
> cost in accessing the invalidated cache lines afterwards, which is
> likely going to be much higher than the cost of an indirect branch".
> And indeed, there's no performance difference with GMAC and EMMC per
> my test on Sipeed Lichee Pi 4A board.
> 
> [...]

Here is the summary with links:
  - [RESEND,v4,1/2] riscv: errata: thead: use riscv_nonstd_cache_ops for CMO
    https://git.kernel.org/riscv/c/a4ff64edf9ed
  - [RESEND,v4,2/2] riscv: errata: thead: use pa based instructions for CMO
    https://git.kernel.org/riscv/c/3690492612ec

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html



_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv