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[PATCH V2] clocksource: riscv: Patch riscv_clock_next_event() jump before first use

Matt Evans posted 1 patch 2 years, 7 months ago 
drivers/clocksource/timer-riscv.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
[PATCH V2] clocksource: riscv: Patch riscv_clock_next_event() jump before first use
Posted by Matt Evans 2 years, 7 months ago 
A static key is used to select between SBI and Sstc timer usage in
riscv_clock_next_event(), but currently the direction is resolved
after cpuhp_setup_state() is called (which sets the next event).  The
first event will therefore fall through the sbi_set_timer() path; this
breaks Sstc-only systems.  So, apply the jump patching before first
use.

Fixes: 9f7a8ff6391f ("RISC-V: Prefer sstc extension if available")
Signed-off-by: Matt Evans <mev@rivosinc.com>
---

V1 -> V2: Commit msg tweak.

 drivers/clocksource/timer-riscv.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 969a552da8d2..a36d173fd6cd 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -177,6 +177,11 @@ static int __init riscv_timer_init_dt(struct device_node *n)
 		return error;
 	}
 
+	if (riscv_isa_extension_available(NULL, SSTC)) {
+		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
+		static_branch_enable(&riscv_sstc_available);
+	}
+
 	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
 			 "clockevents/riscv/timer:starting",
 			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
@@ -184,11 +189,6 @@ static int __init riscv_timer_init_dt(struct device_node *n)
 		pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
 		       error);
 
-	if (riscv_isa_extension_available(NULL, SSTC)) {
-		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
-		static_branch_enable(&riscv_sstc_available);
-	}
-
 	return error;
 }
 
-- 
2.30.2
Re: [PATCH V2] clocksource: riscv: Patch riscv_clock_next_event() jump before first use
Posted by Palmer Dabbelt 2 years, 7 months ago 
On Wed, 01 Feb 2023 11:49:42 PST (-0800), Matt Evans wrote:
> A static key is used to select between SBI and Sstc timer usage in
> riscv_clock_next_event(), but currently the direction is resolved
> after cpuhp_setup_state() is called (which sets the next event).  The
> first event will therefore fall through the sbi_set_timer() path; this
> breaks Sstc-only systems.  So, apply the jump patching before first
> use.
>
> Fixes: 9f7a8ff6391f ("RISC-V: Prefer sstc extension if available")
> Signed-off-by: Matt Evans <mev@rivosinc.com>
> ---
>
> V1 -> V2: Commit msg tweak.
>
>  drivers/clocksource/timer-riscv.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index 969a552da8d2..a36d173fd6cd 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -177,6 +177,11 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>  		return error;
>  	}
>  
> +	if (riscv_isa_extension_available(NULL, SSTC)) {
> +		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
> +		static_branch_enable(&riscv_sstc_available);
> +	}
> +
>  	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
>  			 "clockevents/riscv/timer:starting",
>  			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
> @@ -184,11 +189,6 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>  		pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
>  		       error);
>  
> -	if (riscv_isa_extension_available(NULL, SSTC)) {
> -		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
> -		static_branch_enable(&riscv_sstc_available);
> -	}
> -
>  	return error;
>  }
>  
> -- 
> 2.30.2

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>

Looks like I've taken stuff here before, but I'm also happy to have the 
clocksource folks pick this up so

Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

I don't think this is a particularly critical fix, as IIUC there's still 
no Sstc-only hardware in the real world.  Given how late we are I'd err 
towards putting this on for-next anyway, so I'll give the clocksource 
folks a bit more time to chime in.  Otherwise I'll put it on for-next 
before the merge window (assuming we're got an rc8 coming).

Thanks!
Re: [PATCH V2] clocksource: riscv: Patch riscv_clock_next_event() jump before first use
Posted by Anup Patel 2 years, 7 months ago 
On Thu, Feb 2, 2023 at 1:19 AM Matt Evans <mev@rivosinc.com> wrote:
>
> A static key is used to select between SBI and Sstc timer usage in
> riscv_clock_next_event(), but currently the direction is resolved
> after cpuhp_setup_state() is called (which sets the next event).  The
> first event will therefore fall through the sbi_set_timer() path; this
> breaks Sstc-only systems.  So, apply the jump patching before first
> use.
>
> Fixes: 9f7a8ff6391f ("RISC-V: Prefer sstc extension if available")
> Signed-off-by: Matt Evans <mev@rivosinc.com>

Looks good to me.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

> ---
>
> V1 -> V2: Commit msg tweak.
>
>  drivers/clocksource/timer-riscv.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index 969a552da8d2..a36d173fd6cd 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -177,6 +177,11 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>                 return error;
>         }
>
> +       if (riscv_isa_extension_available(NULL, SSTC)) {
> +               pr_info("Timer interrupt in S-mode is available via sstc extension\n");
> +               static_branch_enable(&riscv_sstc_available);
> +       }
> +
>         error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
>                          "clockevents/riscv/timer:starting",
>                          riscv_timer_starting_cpu, riscv_timer_dying_cpu);
> @@ -184,11 +189,6 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>                 pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
>                        error);
>
> -       if (riscv_isa_extension_available(NULL, SSTC)) {
> -               pr_info("Timer interrupt in S-mode is available via sstc extension\n");
> -               static_branch_enable(&riscv_sstc_available);
> -       }
> -
>         return error;
>  }
>
> --
> 2.30.2
>
>
[tip: timers/core] clocksource/drivers/riscv: Patch riscv_clock_next_event() jump before first use
Posted by tip-bot2 for Matt Evans 2 years, 7 months ago 
The following commit has been merged into the timers/core branch of tip:

Commit-ID:     225b9596cb0227c1c1b1e4a836dad43595c3e61a
Gitweb:        https://git.kernel.org/tip/225b9596cb0227c1c1b1e4a836dad43595c3e61a
Author:        Matt Evans <mev@rivosinc.com>
AuthorDate:    Wed, 01 Feb 2023 19:49:42 
Committer:     Daniel Lezcano <daniel.lezcano@linaro.org>
CommitterDate: Mon, 13 Feb 2023 13:10:17 +01:00

clocksource/drivers/riscv: Patch riscv_clock_next_event() jump before first use

A static key is used to select between SBI and Sstc timer usage in
riscv_clock_next_event(), but currently the direction is resolved
after cpuhp_setup_state() is called (which sets the next event).  The
first event will therefore fall through the sbi_set_timer() path; this
breaks Sstc-only systems.  So, apply the jump patching before first
use.

Fixes: 9f7a8ff6391f ("RISC-V: Prefer sstc extension if available")
Signed-off-by: Matt Evans <mev@rivosinc.com>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/CDDAB2D0-264E-42F3-8E31-BA210BEB8EC1@rivosinc.com
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/clocksource/timer-riscv.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index d8cb629..5f0f10c 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -192,6 +192,11 @@ static int __init riscv_timer_init_dt(struct device_node *n)
 		return error;
 	}
 
+	if (riscv_isa_extension_available(NULL, SSTC)) {
+		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
+		static_branch_enable(&riscv_sstc_available);
+	}
+
 	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
 			 "clockevents/riscv/timer:starting",
 			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
@@ -199,11 +204,6 @@ static int __init riscv_timer_init_dt(struct device_node *n)
 		pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
 		       error);
 
-	if (riscv_isa_extension_available(NULL, SSTC)) {
-		pr_info("Timer interrupt in S-mode is available via sstc extension\n");
-		static_branch_enable(&riscv_sstc_available);
-	}
-
 	return error;
 }

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