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SubjectRe: [PATCH v6 1/4] RISC-V: Add mechanism to provide custom IPI operations
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On Fri, 24 Jul 2020 00:18:19 PDT (-0700), Anup Patel wrote:
> We add mechanism to set custom IPI operations so that CLINT driver
> from drivers directory can provide custom IPI operations.
>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> Tested-by: Emil Renner Berhing <kernel@esmil.dk>
> Reviewed-by: Atish Patra <atish.patra@wdc.com>
> ---
> arch/riscv/include/asm/clint.h | 25 --------------------
> arch/riscv/include/asm/smp.h | 19 +++++++++++++++
> arch/riscv/kernel/clint.c | 23 ++++++++++++++++--
> arch/riscv/kernel/sbi.c | 14 +++++++++++
> arch/riscv/kernel/smp.c | 43 +++++++++++++++++++---------------
> arch/riscv/kernel/smpboot.c | 3 +--
> 6 files changed, 79 insertions(+), 48 deletions(-)
>
> diff --git a/arch/riscv/include/asm/clint.h b/arch/riscv/include/asm/clint.h
> index a279b17a6aad..adaba98a7d6c 100644
> --- a/arch/riscv/include/asm/clint.h
> +++ b/arch/riscv/include/asm/clint.h
> @@ -6,34 +6,9 @@
> #include <linux/smp.h>
>
> #ifdef CONFIG_RISCV_M_MODE
> -extern u32 __iomem *clint_ipi_base;
> -
> void clint_init_boot_cpu(void);
> -
> -static inline void clint_send_ipi_single(unsigned long hartid)
> -{
> - writel(1, clint_ipi_base + hartid);
> -}
> -
> -static inline void clint_send_ipi_mask(const struct cpumask *mask)
> -{
> - int cpu;
> -
> - for_each_cpu(cpu, mask)
> - clint_send_ipi_single(cpuid_to_hartid_map(cpu));
> -}
> -
> -static inline void clint_clear_ipi(unsigned long hartid)
> -{
> - writel(0, clint_ipi_base + hartid);
> -}
> #else /* CONFIG_RISCV_M_MODE */
> #define clint_init_boot_cpu() do { } while (0)
> -
> -/* stubs to for code is only reachable under IS_ENABLED(CONFIG_RISCV_M_MODE): */
> -void clint_send_ipi_single(unsigned long hartid);
> -void clint_send_ipi_mask(const struct cpumask *hartid_mask);
> -void clint_clear_ipi(unsigned long hartid);
> #endif /* CONFIG_RISCV_M_MODE */
>
> #endif /* _ASM_RISCV_CLINT_H */

So this is entirely unrelated to the actual contents of this patch, I'd just
forgotten about it before: the scheme used by clint_init_boot_cpu() only works
once per system reset (and as far as I can tell, that code only works for
two-CPU systems). Not really an issue with this patch set, but we should
probably put a sanity check in the code -- the two-CPU thing should be easy,
but the "only use the CLINT init trick once" thing need some sort of platform
interface.

> diff --git a/arch/riscv/include/asm/smp.h b/arch/riscv/include/asm/smp.h
> index 40bb1c15a731..68de78a8eba6 100644
> --- a/arch/riscv/include/asm/smp.h
> +++ b/arch/riscv/include/asm/smp.h
> @@ -15,6 +15,11 @@
> struct seq_file;
> extern unsigned long boot_cpu_hartid;
>
> +struct riscv_ipi_ops {
> + void (*ipi_inject)(const struct cpumask *target);
> + void (*ipi_clear)(void);
> +};
> +
> #ifdef CONFIG_SMP
> /*
> * Mapping between linux logical cpu index and hartid.
> @@ -40,6 +45,12 @@ void arch_send_call_function_single_ipi(int cpu);
> int riscv_hartid_to_cpuid(int hartid);
> void riscv_cpuid_to_hartid_mask(const struct cpumask *in, struct cpumask *out);
>
> +/* Set custom IPI operations */
> +void riscv_set_ipi_ops(struct riscv_ipi_ops *ops);
> +
> +/* Clear IPI for current CPU */
> +void riscv_clear_ipi(void);
> +
> /*
> * Obtains the hart ID of the currently executing task. This relies on
> * THREAD_INFO_IN_TASK, but we define that unconditionally.
> @@ -78,6 +89,14 @@ static inline void riscv_cpuid_to_hartid_mask(const struct cpumask *in,
> cpumask_set_cpu(boot_cpu_hartid, out);
> }
>
> +static inline void riscv_set_ipi_ops(struct riscv_ipi_ops *ops)
> +{
> +}

It's a bit pedantic, but it seems like this should do something as of this
patch -- even though there's only a single driver, it's odd to have this both
exist and do nothing.

> +
> +static inline void riscv_clear_ipi(void)
> +{
> +}
> +
> #endif /* CONFIG_SMP */
>
> #if defined(CONFIG_HOTPLUG_CPU) && (CONFIG_SMP)
> diff --git a/arch/riscv/kernel/clint.c b/arch/riscv/kernel/clint.c
> index 3647980d14c3..a9845ee023e2 100644
> --- a/arch/riscv/kernel/clint.c
> +++ b/arch/riscv/kernel/clint.c
> @@ -5,11 +5,11 @@
>
> #include <linux/io.h>
> #include <linux/of_address.h>
> +#include <linux/smp.h>
> #include <linux/types.h>
> #include <asm/clint.h>
> #include <asm/csr.h>
> #include <asm/timex.h>
> -#include <asm/smp.h>
>
> /*
> * This is the layout used by the SiFive clint, which is also shared by the qemu
> @@ -21,6 +21,24 @@
>
> u32 __iomem *clint_ipi_base;
>
> +static void clint_send_ipi(const struct cpumask *target)
> +{
> + unsigned int cpu;
> +
> + for_each_cpu(cpu, target)
> + writel(1, clint_ipi_base + cpuid_to_hartid_map(cpu));
> +}
> +
> +static void clint_clear_ipi(void)
> +{
> + writel(0, clint_ipi_base + cpuid_to_hartid_map(smp_processor_id()));
> +}
> +
> +static struct riscv_ipi_ops clint_ipi_ops = {
> + .ipi_inject = clint_send_ipi,
> + .ipi_clear = clint_clear_ipi,
> +};
> +
> void clint_init_boot_cpu(void)
> {
> struct device_node *np;
> @@ -40,5 +58,6 @@ void clint_init_boot_cpu(void)
> riscv_time_cmp = base + CLINT_TIME_CMP_OFF;
> riscv_time_val = base + CLINT_TIME_VAL_OFF;
>
> - clint_clear_ipi(boot_cpu_hartid);
> + clint_clear_ipi();
> + riscv_set_ipi_ops(&clint_ipi_ops);
> }
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index f383ef5672b2..226ccce0f9e0 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -547,6 +547,18 @@ static inline long sbi_get_firmware_version(void)
> return __sbi_base_ecall(SBI_EXT_BASE_GET_IMP_VERSION);
> }
>
> +static void sbi_send_cpumask_ipi(const struct cpumask *target)
> +{
> + struct cpumask hartid_mask;
> +
> + riscv_cpuid_to_hartid_mask(target, &hartid_mask);
> +
> + sbi_send_ipi(cpumask_bits(&hartid_mask));
> +}
> +
> +static struct riscv_ipi_ops sbi_ipi_ops = {
> + .ipi_inject = sbi_send_cpumask_ipi
> +};
>
> int __init sbi_init(void)
> {
> @@ -587,5 +599,7 @@ int __init sbi_init(void)
> __sbi_rfence = __sbi_rfence_v01;
> }
>
> + riscv_set_ipi_ops(&sbi_ipi_ops);
> +
> return 0;
> }
> diff --git a/arch/riscv/kernel/smp.c b/arch/riscv/kernel/smp.c
> index b1d4f452f843..8b85683ce203 100644
> --- a/arch/riscv/kernel/smp.c
> +++ b/arch/riscv/kernel/smp.c
> @@ -84,9 +84,25 @@ static void ipi_stop(void)
> wait_for_interrupt();
> }
>
> +static struct riscv_ipi_ops *ipi_ops;
> +
> +void riscv_set_ipi_ops(struct riscv_ipi_ops *ops)
> +{
> + ipi_ops = ops;
> +}
> +EXPORT_SYMBOL_GPL(riscv_set_ipi_ops);
> +
> +void riscv_clear_ipi(void)
> +{
> + if (ipi_ops && ipi_ops->ipi_clear)
> + ipi_ops->ipi_clear();
> +
> + csr_clear(CSR_IP, IE_SIE);
> +}
> +EXPORT_SYMBOL_GPL(riscv_clear_ipi);
> +
> static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
> {
> - struct cpumask hartid_mask;
> int cpu;
>
> smp_mb__before_atomic();
> @@ -94,33 +110,22 @@ static void send_ipi_mask(const struct cpumask *mask, enum ipi_message_type op)
> set_bit(op, &ipi_data[cpu].bits);
> smp_mb__after_atomic();
>
> - riscv_cpuid_to_hartid_mask(mask, &hartid_mask);
> - if (IS_ENABLED(CONFIG_RISCV_SBI))
> - sbi_send_ipi(cpumask_bits(&hartid_mask));
> + if (ipi_ops && ipi_ops->ipi_inject)
> + ipi_ops->ipi_inject(mask);
> else
> - clint_send_ipi_mask(mask);
> + pr_warn("SMP: IPI inject method not available\n");
> }
>
> static void send_ipi_single(int cpu, enum ipi_message_type op)
> {
> - int hartid = cpuid_to_hartid_map(cpu);
> -
> smp_mb__before_atomic();
> set_bit(op, &ipi_data[cpu].bits);
> smp_mb__after_atomic();
>
> - if (IS_ENABLED(CONFIG_RISCV_SBI))
> - sbi_send_ipi(cpumask_bits(cpumask_of(hartid)));
> - else
> - clint_send_ipi_single(hartid);
> -}
> -
> -static inline void clear_ipi(void)
> -{
> - if (IS_ENABLED(CONFIG_RISCV_SBI))
> - csr_clear(CSR_IP, IE_SIE);
> + if (ipi_ops && ipi_ops->ipi_inject)
> + ipi_ops->ipi_inject(cpumask_of(cpu));
> else
> - clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
> + pr_warn("SMP: IPI inject method not available\n");
> }
>
> void handle_IPI(struct pt_regs *regs)
> @@ -131,7 +136,7 @@ void handle_IPI(struct pt_regs *regs)
>
> irq_enter();
>
> - clear_ipi();
> + riscv_clear_ipi();
>
> while (true) {
> unsigned long ops;
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index 4e9922790f6e..5fe849791bf0 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -147,8 +147,7 @@ asmlinkage __visible void smp_callin(void)
> {
> struct mm_struct *mm = &init_mm;
>
> - if (!IS_ENABLED(CONFIG_RISCV_SBI))
> - clint_clear_ipi(cpuid_to_hartid_map(smp_processor_id()));
> + riscv_clear_ipi();
>
> /* All kernel threads share the same mm context. */
> mmgrab(mm);

I don't really care that much, though, so:

Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>

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