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authorAtish Patra <atishp@rivosinc.com>2022-07-22 09:50:46 -0700
committerPalmer Dabbelt <palmer@rivosinc.com>2022-08-11 14:36:55 -0700
commit9f7a8ff6391fd5363363b8e5c8b1462a07922368 (patch)
tree6ea3c4b80dbecb0de1071c630daafe6babc34090 /drivers
parent464b0187ff94fcc629fe7cd350e16a3b9e80ed9e (diff)
RISC-V: Prefer sstc extension if available
RISC-V ISA has sstc extension which allows updating the next clock event via a CSR (stimecmp) instead of an SBI call. This should happen dynamically if sstc extension is available. Otherwise, it will fallback to SBI call to maintain backward compatibility. Reviewed-by: Anup Patel <anup@brainfault.org> Signed-off-by: Atish Patra <atishp@rivosinc.com> Reviewed-by: Guo Ren <guoren@kernel.org> Link: https://lore.kernel.org/r/20220722165047.519994-4-atishp@rivosinc.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/clocksource/timer-riscv.c25
1 files changed, 24 insertions, 1 deletions
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 593d5a957b69..05f6cf067289 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -7,6 +7,9 @@
* either be read from the "time" and "timeh" CSRs, and can use the SBI to
* setup events, or directly accessed using MMIO registers.
*/
+
+#define pr_fmt(fmt) "riscv-timer: " fmt
+
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/cpu.h>
@@ -20,14 +23,28 @@
#include <linux/of_irq.h>
#include <clocksource/timer-riscv.h>
#include <asm/smp.h>
+#include <asm/hwcap.h>
#include <asm/sbi.h>
#include <asm/timex.h>
+static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
+
static int riscv_clock_next_event(unsigned long delta,
struct clock_event_device *ce)
{
+ u64 next_tval = get_cycles64() + delta;
+
csr_set(CSR_IE, IE_TIE);
- sbi_set_timer(get_cycles64() + delta);
+ if (static_branch_likely(&riscv_sstc_available)) {
+#if defined(CONFIG_32BIT)
+ csr_write(CSR_STIMECMP, next_tval & 0xFFFFFFFF);
+ csr_write(CSR_STIMECMPH, next_tval >> 32);
+#else
+ csr_write(CSR_STIMECMP, next_tval);
+#endif
+ } else
+ sbi_set_timer(next_tval);
+
return 0;
}
@@ -165,6 +182,12 @@ static int __init riscv_timer_init_dt(struct device_node *n)
if (error)
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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