From: Kyung Min Park <kyung.min.park@intel.com>
To: x86@kernel.org, linux-kernel@vger.kernel.org
Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
gregkh@linuxfoundation.org, ak@linux.intel.com,
tony.luck@intel.com, ashok.raj@intel.com,
ravi.v.shankar@intel.com, fenghua.yu@intel.com
Subject: [PATCH 1/2] x86/asm: Define a few helpers in delay_waitx()
Date: Wed, 26 Feb 2020 11:10:57 -0800 [thread overview]
Message-ID: <1582744258-42744-2-git-send-email-kyung.min.park@intel.com> (raw)
In-Reply-To: <1582744258-42744-1-git-send-email-kyung.min.park@intel.com>
Refactor code to make it easier to add a new model specific function to
delay for a number of cycles.
No functional change.
Reviewed-by: Tony Luck <tony.luck@intel.com>
Co-developed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Kyung Min Park <kyung.min.park@intel.com>
---
arch/x86/lib/delay.c | 58 +++++++++++++++++++++++++++++++++-------------------
1 file changed, 37 insertions(+), 21 deletions(-)
diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c
index c126571..6be29cf 100644
--- a/arch/x86/lib/delay.c
+++ b/arch/x86/lib/delay.c
@@ -90,9 +90,36 @@ static void delay_tsc(unsigned long __loops)
* counts with TSC frequency. The input value is the loop of the
* counter, it will exit when the timer expires.
*/
-static void delay_mwaitx(unsigned long __loops)
+static void mwaitx(u64 unused, u64 loops)
{
- u64 start, end, delay, loops = __loops;
+ u64 delay;
+
+ delay = min_t(u64, MWAITX_MAX_LOOPS, loops);
+ /*
+ * Use cpu_tss_rw as a cacheline-aligned, seldomly
+ * accessed per-cpu variable as the monitor target.
+ */
+ __monitorx(raw_cpu_ptr(&cpu_tss_rw), 0, 0);
+
+ /*
+ * AMD, like Intel, supports the EAX hint and EAX=0xf
+ * means, do not enter any deep C-state and we use it
+ * here in delay() to minimize wakeup latency.
+ */
+ __mwaitx(MWAITX_DISABLE_CSTATES, delay, MWAITX_ECX_TIMER_ENABLE);
+}
+
+static void (*wait_func)(u64, u64);
+
+/*
+ * Call a vendor specific function to delay for a given
+ * amount of time. Because these functions may return
+ * earlier than requested, check for actual elapsed time
+ * and call again until done.
+ */
+static void delay_iterate(unsigned long __loops)
+{
+ u64 start, end, loops = __loops;
/*
* Timer value of 0 causes MWAITX to wait indefinitely, unless there
@@ -104,20 +131,8 @@ static void delay_mwaitx(unsigned long __loops)
start = rdtsc_ordered();
for (;;) {
- delay = min_t(u64, MWAITX_MAX_LOOPS, loops);
-
- /*
- * Use cpu_tss_rw as a cacheline-aligned, seldomly
- * accessed per-cpu variable as the monitor target.
- */
- __monitorx(raw_cpu_ptr(&cpu_tss_rw), 0, 0);
- /*
- * AMD, like Intel's MWAIT version, supports the EAX hint and
- * EAX=0xf0 means, do not enter any deep C-state and we use it
- * here in delay() to minimize wakeup latency.
- */
- __mwaitx(MWAITX_DISABLE_CSTATES, delay, MWAITX_ECX_TIMER_ENABLE);
+ wait_func(start, loops);
end = rdtsc_ordered();
@@ -134,22 +149,23 @@ static void delay_mwaitx(unsigned long __loops)
* Since we calibrate only once at boot, this
* function should be set once at boot and not changed
*/
-static void (*delay_fn)(unsigned long) = delay_loop;
+static void (*delay_platform)(unsigned long) = delay_loop;
void use_tsc_delay(void)
{
- if (delay_fn == delay_loop)
- delay_fn = delay_tsc;
+ if (delay_platform == delay_loop)
+ delay_platform = delay_tsc;
}
void use_mwaitx_delay(void)
{
- delay_fn = delay_mwaitx;
+ wait_func = mwaitx;
+ delay_platform = delay_iterate;
}
int read_current_timer(unsigned long *timer_val)
{
- if (delay_fn == delay_tsc) {
+ if (delay_platform == delay_tsc) {
*timer_val = rdtsc();
return 0;
}
@@ -158,7 +174,7 @@ int read_current_timer(unsigned long *timer_val)
void __delay(unsigned long loops)
{
- delay_fn(loops);
+ delay_platform(loops);
}
EXPORT_SYMBOL(__delay);
--
2.7.4
next prev parent reply other threads:[~2020-02-26 19:11 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 19:10 [PATCH 0/2] x86/delay: Introduce TPAUSE instruction Kyung Min Park
2020-02-26 19:10 ` Kyung Min Park [this message]
2020-03-18 20:19 ` [PATCH 1/2] x86/asm: Define a few helpers in delay_waitx() Thomas Gleixner
2020-02-26 19:10 ` [PATCH 2/2] x86/asm/delay: Introduce TPAUSE delay Kyung Min Park
2020-02-26 21:10 ` Andi Kleen
2020-02-26 21:20 ` Luck, Tony
2020-02-26 21:59 ` Andi Kleen
2020-02-26 21:31 ` Fenghua Yu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1582744258-42744-2-git-send-email-kyung.min.park@intel.com \
--to=kyung.min.park@intel.com \
--cc=ak@linux.intel.com \
--cc=ashok.raj@intel.com \
--cc=fenghua.yu@intel.com \
--cc=gregkh@linuxfoundation.org \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=ravi.v.shankar@intel.com \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).