[PATCH v6 0/2] riscv_pmu_sbi: add support for PMU variant on T-Head C9xx cores

[PATCH v6 0/2] riscv_pmu_sbi: add support for PMU variant on T-Head C9xx cores

[Heiko Stuebner]

The PMU on T-Head C9xx cores is quite similar to the SSCOFPMF extension
but not completely identical, so this series

changes in v6:
- follow Anup's suggestion and hook into the (pending) cpuinfo patch [2]
  instead of modifying the core sbi_get_* functions

changes in v5:
- add received Reviews
- fix sbi caching wrt. negative values (Drew)
- add comment about specific c9xx arch- and imp-ids (Conor)

changes in v4:
- add new patch to cache sbi mvendor, march and mimp-ids (Atish)
- errata dependencies in one line (Conor)
- make driver detection conditional on CONFIG_ERRATA_THEAD_PMU too (Atish)

changes in v3:
- improve commit message (Atish, Conor)
- IS_ENABLED and BIT() in errata probe (Conor)

The change depends on my cpufeature/t-head errata probe cleanup series [1].


changes in v2:
- use alternatives for the CSR access
- make the irq num selection a bit nicer

There is of course a matching opensbi-part whose most recent implementation
can be found on [0].


[0] https://patchwork.ozlabs.org/project/opensbi/cover/20221004164227.1381825-1-heiko@sntech.de
[1] https://lore.kernel.org/all/20220905111027.2463297-1-heiko@sntech.de/
[2] https://lore.kernel.org/r/20220727043829.151794-1-apatel@ventanamicro.com

Heiko Stuebner (2):
  RISC-V: Cache SBI vendor values
  drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head
    C9xx cores

 arch/riscv/Kconfig.erratas           | 13 +++++++++++
 arch/riscv/errata/thead/errata.c     | 19 ++++++++++++++++
 arch/riscv/include/asm/errata_list.h | 16 ++++++++++++-
 arch/riscv/include/asm/sbi.h         |  5 ++++
 arch/riscv/kernel/cpu.c              | 30 +++++++++++++++++++++---
 drivers/perf/riscv_pmu_sbi.c         | 34 ++++++++++++++++++++--------
 6 files changed, 103 insertions(+), 14 deletions(-)

-- 
2.35.1


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[PATCH v6 1/2] RISC-V: Cache SBI vendor values

[Heiko Stuebner]

sbi_get_mvendorid(), sbi_get_marchid() and sbi_get_mimpid() might get
called multiple times, though the values of these CSRs should not change
during the runtime of a specific machine.

Though the values can be different depending on which hart of the system
they get called. So hook into the newly introduced cpuinfo struct to allow
retrieving these cached values via new functions.

Also use arch_initcall for the cpuinfo setup instead, as that now clearly
is "architecture specific initialization" and also makes these information
available slightly earlier.

[caching vendor ids]
Suggested-by: Atish Patra <atishp@atishpatra.org>
[using cpuinfo struct as cache]
Suggested-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
---
 arch/riscv/include/asm/sbi.h |  5 +++++
 arch/riscv/kernel/cpu.c      | 30 +++++++++++++++++++++++++++---
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
index 2a0ef738695e..4ca7fbacff42 100644
--- a/arch/riscv/include/asm/sbi.h
+++ b/arch/riscv/include/asm/sbi.h
@@ -327,4 +327,9 @@ int sbi_err_map_linux_errno(int err);
 static inline int sbi_remote_fence_i(const struct cpumask *cpu_mask) { return -1; }
 static inline void sbi_init(void) {}
 #endif /* CONFIG_RISCV_SBI */
+
+unsigned long riscv_cached_mvendorid(unsigned int cpu_id);
+unsigned long riscv_cached_marchid(unsigned int cpu_id);
+unsigned long riscv_cached_mimpid(unsigned int cpu_id);
+
 #endif /* _ASM_RISCV_SBI_H */
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index 250220e2cceb..2c40763e1cc8 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -70,8 +70,6 @@ int riscv_of_parent_hartid(struct device_node *node, unsigned long *hartid)
 	return -1;
 }
 
-#ifdef CONFIG_PROC_FS
-
 struct riscv_cpuinfo {
 	unsigned long mvendorid;
 	unsigned long marchid;
@@ -79,6 +77,30 @@ struct riscv_cpuinfo {
 };
 static DEFINE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
 
+unsigned long riscv_cached_mvendorid(unsigned int cpu_id)
+{
+	struct riscv_cpuinfo *ci = per_cpu_ptr(&riscv_cpuinfo, cpu_id);
+
+	return ci->mvendorid;
+}
+EXPORT_SYMBOL(riscv_cached_mvendorid);
+
+unsigned long riscv_cached_marchid(unsigned int cpu_id)
+{
+	struct riscv_cpuinfo *ci = per_cpu_ptr(&riscv_cpuinfo, cpu_id);
+
+	return ci->marchid;
+}
+EXPORT_SYMBOL(riscv_cached_marchid);
+
+unsigned long riscv_cached_mimpid(unsigned int cpu_id)
+{
+	struct riscv_cpuinfo *ci = per_cpu_ptr(&riscv_cpuinfo, cpu_id);
+
+	return ci->mimpid;
+}
+EXPORT_SYMBOL(riscv_cached_mimpid);
+
 static int riscv_cpuinfo_starting(unsigned int cpu)
 {
 	struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
@@ -113,7 +135,9 @@ static int __init riscv_cpuinfo_init(void)
 
 	return 0;
 }
-device_initcall(riscv_cpuinfo_init);
+arch_initcall(riscv_cpuinfo_init);
+
+#ifdef CONFIG_PROC_FS
 
 #define __RISCV_ISA_EXT_DATA(UPROP, EXTID) \
 	{							\
-- 
2.35.1


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[PATCH v6 2/2] drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head C9xx cores

[Heiko Stuebner]

With the T-HEAD C9XX cores being designed before or during the ratification
to the SSCOFPMF extension, it implements functionality very similar but
not equal to it.

It implements overflow handling and also some privilege-mode filtering.
While SSCOFPMF supports this for all modes, the C9XX only implements the
filtering for M-mode and S-mode but not user-mode.

So add some adaptions to allow the C9XX to still handle
its PMU through the regular SBI PMU interface instead of defining new
interfaces or drivers.

To work properly, this requires a matching change in SBI, though the actual
interface between kernel and SBI does not change.

The main differences are a the overflow CSR and irq number.

As the reading of the overflow-csr is in the hot-path during irq handling,
use an errata and alternatives to not introduce new conditionals there.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
---
 arch/riscv/Kconfig.erratas           | 13 +++++++++++
 arch/riscv/errata/thead/errata.c     | 19 ++++++++++++++++
 arch/riscv/include/asm/errata_list.h | 16 ++++++++++++-
 drivers/perf/riscv_pmu_sbi.c         | 34 ++++++++++++++++++++--------
 4 files changed, 71 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
index f3623df23b5f..69621ae6d647 100644
--- a/arch/riscv/Kconfig.erratas
+++ b/arch/riscv/Kconfig.erratas
@@ -66,4 +66,17 @@ config ERRATA_THEAD_CMO
 
 	  If you don't know what to do here, say "Y".
 
+config ERRATA_THEAD_PMU
+	bool "Apply T-Head PMU errata"
+	depends on ERRATA_THEAD && RISCV_PMU_SBI
+	default y
+	help
+	  The T-Head C9xx cores implement a PMU overflow extension very
+	  similar to the core SSCOFPMF extension.
+
+	  This will apply the overflow errata to handle the non-standard
+	  behaviour via the regular SBI PMU driver and interface.
+
+	  If you don't know what to do here, say "Y".
+
 endmenu # "CPU errata selection"
diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
index 21546937db39..fac5742d1c1e 100644
--- a/arch/riscv/errata/thead/errata.c
+++ b/arch/riscv/errata/thead/errata.c
@@ -47,6 +47,22 @@ static bool errata_probe_cmo(unsigned int stage,
 	return true;
 }
 
+static bool errata_probe_pmu(unsigned int stage,
+			     unsigned long arch_id, unsigned long impid)
+{
+	if (!IS_ENABLED(CONFIG_ERRATA_THEAD_PMU))
+		return false;
+
+	/* target-c9xx cores report arch_id and impid as 0 */
+	if (arch_id != 0 || impid != 0)
+		return false;
+
+	if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+		return false;
+
+	return true;
+}
+
 static u32 thead_errata_probe(unsigned int stage,
 			      unsigned long archid, unsigned long impid)
 {
@@ -58,6 +74,9 @@ static u32 thead_errata_probe(unsigned int stage,
 	if (errata_probe_cmo(stage, archid, impid))
 		cpu_req_errata |= BIT(ERRATA_THEAD_CMO);
 
+	if (errata_probe_pmu(stage, archid, impid))
+		cpu_req_errata |= BIT(ERRATA_THEAD_PMU);
+
 	return cpu_req_errata;
 }
 
diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
index 19a771085781..4180312d2a70 100644
--- a/arch/riscv/include/asm/errata_list.h
+++ b/arch/riscv/include/asm/errata_list.h
@@ -6,6 +6,7 @@
 #define ASM_ERRATA_LIST_H
 
 #include <asm/alternative.h>
+#include <asm/csr.h>
 #include <asm/vendorid_list.h>
 
 #ifdef CONFIG_ERRATA_SIFIVE
@@ -17,7 +18,8 @@
 #ifdef CONFIG_ERRATA_THEAD
 #define	ERRATA_THEAD_PBMT 0
 #define	ERRATA_THEAD_CMO 1
-#define	ERRATA_THEAD_NUMBER 2
+#define	ERRATA_THEAD_PMU 2
+#define	ERRATA_THEAD_NUMBER 3
 #endif
 
 #define	CPUFEATURE_SVPBMT 0
@@ -142,6 +144,18 @@ asm volatile(ALTERNATIVE_2(						\
 	    "r"((unsigned long)(_start) + (_size))			\
 	: "a0")
 
+#define THEAD_C9XX_RV_IRQ_PMU			17
+#define THEAD_C9XX_CSR_SCOUNTEROF		0x5c5
+
+#define ALT_SBI_PMU_OVERFLOW(__ovl)					\
+asm volatile(ALTERNATIVE(						\
+	"csrr %0, " __stringify(CSR_SSCOUNTOVF),			\
+	"csrr %0, " __stringify(THEAD_C9XX_CSR_SCOUNTEROF),		\
+		THEAD_VENDOR_ID, ERRATA_THEAD_PMU,			\
+		CONFIG_ERRATA_THEAD_PMU)				\
+	: "=r" (__ovl) :						\
+	: "memory")
+
 #endif /* __ASSEMBLY__ */
 
 #endif
diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 8de4ca2fef21..a77fef6dc35f 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -19,6 +19,7 @@
 #include <linux/of.h>
 #include <linux/cpu_pm.h>
 
+#include <asm/errata_list.h>
 #include <asm/sbi.h>
 #include <asm/hwcap.h>
 
@@ -46,6 +47,8 @@ static const struct attribute_group *riscv_pmu_attr_groups[] = {
  * per_cpu in case of harts with different pmu counters
  */
 static union sbi_pmu_ctr_info *pmu_ctr_list;
+static bool riscv_pmu_use_irq;
+static unsigned int riscv_pmu_irq_num;
 static unsigned int riscv_pmu_irq;
 
 struct sbi_pmu_event_data {
@@ -575,7 +578,7 @@ static irqreturn_t pmu_sbi_ovf_handler(int irq, void *dev)
 	fidx = find_first_bit(cpu_hw_evt->used_hw_ctrs, RISCV_MAX_COUNTERS);
 	event = cpu_hw_evt->events[fidx];
 	if (!event) {
-		csr_clear(CSR_SIP, SIP_LCOFIP);
+		csr_clear(CSR_SIP, BIT(riscv_pmu_irq_num));
 		return IRQ_NONE;
 	}
 
@@ -583,13 +586,13 @@ static irqreturn_t pmu_sbi_ovf_handler(int irq, void *dev)
 	pmu_sbi_stop_hw_ctrs(pmu);
 
 	/* Overflow status register should only be read after counter are stopped */
-	overflow = csr_read(CSR_SSCOUNTOVF);
+	ALT_SBI_PMU_OVERFLOW(overflow);
 
 	/*
 	 * Overflow interrupt pending bit should only be cleared after stopping
 	 * all the counters to avoid any race condition.
 	 */
-	csr_clear(CSR_SIP, SIP_LCOFIP);
+	csr_clear(CSR_SIP, BIT(riscv_pmu_irq_num));
 
 	/* No overflow bit is set */
 	if (!overflow)
@@ -651,10 +654,10 @@ static int pmu_sbi_starting_cpu(unsigned int cpu, struct hlist_node *node)
 	/* Stop all the counters so that they can be enabled from perf */
 	pmu_sbi_stop_all(pmu);
 
-	if (riscv_isa_extension_available(NULL, SSCOFPMF)) {
+	if (riscv_pmu_use_irq) {
 		cpu_hw_evt->irq = riscv_pmu_irq;
-		csr_clear(CSR_IP, BIT(RV_IRQ_PMU));
-		csr_set(CSR_IE, BIT(RV_IRQ_PMU));
+		csr_clear(CSR_IP, BIT(riscv_pmu_irq_num));
+		csr_set(CSR_IE, BIT(riscv_pmu_irq_num));
 		enable_percpu_irq(riscv_pmu_irq, IRQ_TYPE_NONE);
 	}
 
@@ -663,9 +666,9 @@ static int pmu_sbi_starting_cpu(unsigned int cpu, struct hlist_node *node)
 
 static int pmu_sbi_dying_cpu(unsigned int cpu, struct hlist_node *node)
 {
-	if (riscv_isa_extension_available(NULL, SSCOFPMF)) {
+	if (riscv_pmu_use_irq) {
 		disable_percpu_irq(riscv_pmu_irq);
-		csr_clear(CSR_IE, BIT(RV_IRQ_PMU));
+		csr_clear(CSR_IE, BIT(riscv_pmu_irq_num));
 	}
 
 	/* Disable all counters access for user mode now */
@@ -681,7 +684,18 @@ static int pmu_sbi_setup_irqs(struct riscv_pmu *pmu, struct platform_device *pde
 	struct device_node *cpu, *child;
 	struct irq_domain *domain = NULL;
 
-	if (!riscv_isa_extension_available(NULL, SSCOFPMF))
+	if (riscv_isa_extension_available(NULL, SSCOFPMF)) {
+		riscv_pmu_irq_num = RV_IRQ_PMU;
+		riscv_pmu_use_irq = true;
+	} else if (IS_ENABLED(CONFIG_ERRATA_THEAD_PMU) &&
+		   riscv_cached_mvendorid(0) == THEAD_VENDOR_ID &&
+		   riscv_cached_marchid(0) == 0 &&
+		   riscv_cached_mimpid(0) == 0) {
+		riscv_pmu_irq_num = THEAD_C9XX_RV_IRQ_PMU;
+		riscv_pmu_use_irq = true;
+	}
+
+	if (!riscv_pmu_use_irq)
 		return -EOPNOTSUPP;
 
 	for_each_of_cpu_node(cpu) {
@@ -703,7 +717,7 @@ static int pmu_sbi_setup_irqs(struct riscv_pmu *pmu, struct platform_device *pde
 		return -ENODEV;
 	}
 
-	riscv_pmu_irq = irq_create_mapping(domain, RV_IRQ_PMU);
+	riscv_pmu_irq = irq_create_mapping(domain, riscv_pmu_irq_num);
 	if (!riscv_pmu_irq) {
 		pr_err("Failed to map PMU interrupt for node\n");
 		return -ENODEV;
-- 
2.35.1


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Re: [PATCH v6 0/2] riscv_pmu_sbi: add support for PMU variant on T-Head C9xx cores

[Palmer Dabbelt]

On Tue, 11 Oct 2022 16:18:39 PDT (-0700), heiko@sntech.de wrote:
> The PMU on T-Head C9xx cores is quite similar to the SSCOFPMF extension
> but not completely identical, so this series

The rest of that sentance got dropped, so I put in

    The PMU on T-Head C9xx cores is quite similar to the SSCOFPMF extension
    but not completely identical, so this series adds a T-Head PMU errata
    that handlen the differences.

but LMK if you had a better version, it's still early so I don't mind 
swapping it around.

b4 also got kind of confused here so I had to merge suff manually.

> changes in v6:
> - follow Anup's suggestion and hook into the (pending) cpuinfo patch [2]
>   instead of modifying the core sbi_get_* functions
>
> changes in v5:
> - add received Reviews
> - fix sbi caching wrt. negative values (Drew)
> - add comment about specific c9xx arch- and imp-ids (Conor)
>
> changes in v4:
> - add new patch to cache sbi mvendor, march and mimp-ids (Atish)
> - errata dependencies in one line (Conor)
> - make driver detection conditional on CONFIG_ERRATA_THEAD_PMU too (Atish)
>
> changes in v3:
> - improve commit message (Atish, Conor)
> - IS_ENABLED and BIT() in errata probe (Conor)
>
> The change depends on my cpufeature/t-head errata probe cleanup series [1].
>
>
> changes in v2:
> - use alternatives for the CSR access
> - make the irq num selection a bit nicer
>
> There is of course a matching opensbi-part whose most recent implementation
> can be found on [0].
>
>
> [0] https://patchwork.ozlabs.org/project/opensbi/cover/20221004164227.1381825-1-heiko@sntech.de
> [1] https://lore.kernel.org/all/20220905111027.2463297-1-heiko@sntech.de/
> [2] https://lore.kernel.org/r/20220727043829.151794-1-apatel@ventanamicro.com
>
> Heiko Stuebner (2):
>   RISC-V: Cache SBI vendor values
>   drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head
>     C9xx cores
>
>  arch/riscv/Kconfig.erratas           | 13 +++++++++++
>  arch/riscv/errata/thead/errata.c     | 19 ++++++++++++++++
>  arch/riscv/include/asm/errata_list.h | 16 ++++++++++++-
>  arch/riscv/include/asm/sbi.h         |  5 ++++
>  arch/riscv/kernel/cpu.c              | 30 +++++++++++++++++++++---
>  drivers/perf/riscv_pmu_sbi.c         | 34 ++++++++++++++++++++--------
>  6 files changed, 103 insertions(+), 14 deletions(-)

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Re: [PATCH v6 0/2] riscv_pmu_sbi: add support for PMU variant on T-Head C9xx cores

[Heiko Stübner]

Am Donnerstag, 27. Oktober 2022, 07:02:59 CEST schrieb Palmer Dabbelt:
> On Tue, 11 Oct 2022 16:18:39 PDT (-0700), heiko@sntech.de wrote:
> > The PMU on T-Head C9xx cores is quite similar to the SSCOFPMF extension
> > but not completely identical, so this series
> 
> The rest of that sentance got dropped, so I put in
> 
>     The PMU on T-Head C9xx cores is quite similar to the SSCOFPMF extension
>     but not completely identical, so this series adds a T-Head PMU errata
>     that handlen the differences.
> 
> but LMK if you had a better version, it's still early so I don't mind 
> swapping it around.

sounds just fine and sorry for not finishing that sentence on my own.


> b4 also got kind of confused here so I had to merge suff manually.

do you still know what b4 complained about?

My patch workflow is pretty basic (git format-patch + separate
git send-email) so I guess it might be interesting what it was
stumbling on.

Thanks
Heiko


> > changes in v6:
> > - follow Anup's suggestion and hook into the (pending) cpuinfo patch [2]
> >   instead of modifying the core sbi_get_* functions
> >
> > changes in v5:
> > - add received Reviews
> > - fix sbi caching wrt. negative values (Drew)
> > - add comment about specific c9xx arch- and imp-ids (Conor)
> >
> > changes in v4:
> > - add new patch to cache sbi mvendor, march and mimp-ids (Atish)
> > - errata dependencies in one line (Conor)
> > - make driver detection conditional on CONFIG_ERRATA_THEAD_PMU too (Atish)
> >
> > changes in v3:
> > - improve commit message (Atish, Conor)
> > - IS_ENABLED and BIT() in errata probe (Conor)
> >
> > The change depends on my cpufeature/t-head errata probe cleanup series [1].
> >
> >
> > changes in v2:
> > - use alternatives for the CSR access
> > - make the irq num selection a bit nicer
> >
> > There is of course a matching opensbi-part whose most recent implementation
> > can be found on [0].
> >
> >
> > [0] https://patchwork.ozlabs.org/project/opensbi/cover/20221004164227.1381825-1-heiko@sntech.de
> > [1] https://lore.kernel.org/all/20220905111027.2463297-1-heiko@sntech.de/
> > [2] https://lore.kernel.org/r/20220727043829.151794-1-apatel@ventanamicro.com
> >
> > Heiko Stuebner (2):
> >   RISC-V: Cache SBI vendor values
> >   drivers/perf: riscv_pmu_sbi: add support for PMU variant on T-Head
> >     C9xx cores
> >
> >  arch/riscv/Kconfig.erratas           | 13 +++++++++++
> >  arch/riscv/errata/thead/errata.c     | 19 ++++++++++++++++
> >  arch/riscv/include/asm/errata_list.h | 16 ++++++++++++-
> >  arch/riscv/include/asm/sbi.h         |  5 ++++
> >  arch/riscv/kernel/cpu.c              | 30 +++++++++++++++++++++---
> >  drivers/perf/riscv_pmu_sbi.c         | 34 ++++++++++++++++++++--------
> >  6 files changed, 103 insertions(+), 14 deletions(-)
> 





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