Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1367804
| Path | csiph.com!goblin3!goblin-spool!goblin2!goblin.stu.neva.ru!gothmog.csi.it!bofh.it!news.nic.it!robomod |
|---|---|
| From | Len Brown <lenb@kernel.org> |
| Newsgroups | linux.kernel |
| Subject | [PATCH 9/9] x86 tsc: enumerate BXT tsc_khz via CPUID |
| Date | Thu, 31 Mar 2016 06:20:03 +0200 |
| Message-ID | <riCfp-7Lb-13@gated-at.bofh.it> (permalink) |
| References | <riCfn-7Lb-3@gated-at.bofh.it> |
| X-Original-To | x86@kernel.org |
| Dkim-Signature | v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references :in-reply-to:references:reply-to:organization; bh=zxS54KBj6Inhng45pxfjkTikzSvnAkE8NbZrkrsWujw=; b=VPPgmUCxvKmKXC7/ysv2ika83VjmAmsc7vQ4Q22nI0dFEetVjK+NgEoYOhoe3R33D8 ZDi+y3llb2k0LOFHLGOjQpEZS3hhv5qLx+iZRFnL4oROst9UGWGxd84vJzSiMjzzDO7q otL9Z5zSgOA582QZTz+ZoFPBxdVXvEWZmkkOQEiRb9tSbQoqhoJ6rxdf41yE5ioI1VSC ilcBEdYNS9vHZ6aqzyB9tZI0PxZZtzy/FCyzcQz5z2w2OCsMcl2cZ7Ok8y1Zwv4RGHEH MvX5YQnESR0uVa7AlQlZicmswUE9UII9K3v7GAYVq+h+yrQ616rdTpaA3sFGRHFwPVod FWPA== |
| X-Google-Dkim-Signature | v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :in-reply-to:references:in-reply-to:references:reply-to:organization; bh=zxS54KBj6Inhng45pxfjkTikzSvnAkE8NbZrkrsWujw=; b=LPIYBz8nFO6HC6Wg5hPxD1YvoxrntnvNjJtu24AigzzPzv9uy26RuvUiwaNZGgLB3t RMFM7KqlE/B7qIR8xuf6bA+1lw0zl/gshULBqi475ThICESCIXm6kxEjayzwr0AzM5tH S/dX7OzR5uvKkhlrz8p99rXbxA18Z5enZHFuHR2IdhKs2PvUSpFdRyYc8FbWUIkEIlkl qe/lJgpZYcHqXPmnCUkIkoG6Df0KqZngj6hnLqfGrNVYjq4gbGnY0N8+9HCEFRcT8fOL Lgs4CvtKVMZpB41+PUj42Ktnuu30u1SjkOKHJeqE9mCmosMQQINcdGS5rF9R2rEjoPWy 73ng== |
| X-Gm-Message-State | AD7BkJIpclEvXQ64b7oJ0iTCV7h0ezESNpFxsXZwK05gY13PbmAedjea3mgj45+CLehfzA== |
| X-Received | by 10.37.230.135 with SMTP id d129mr6635880ybh.74.1459397681602; Wed, 30 Mar 2016 21:14:41 -0700 (PDT) |
| X-Mailer | git-send-email 2.8.0.rc4.16.g56331f8 |
| Reply-To | Len Brown <lenb@kernel.org> |
| Organization | Intel Open Source Technology Center |
| Sender | robomod@news.nic.it |
| List-ID | <linux-kernel.vger.kernel.org> |
| X-Mailing-List | linux-kernel@vger.kernel.org |
| Approved | robomod@news.nic.it |
| Lines | 64 |
| X-Original-Cc | linux-kernel@vger.kernel.org, Bin Gao <bin.gao@intel.com>, Len Brown <len.brown@intel.com> |
| X-Original-Date | Thu, 31 Mar 2016 00:13:55 -0400 |
| X-Original-Message-ID | <3152b94afb8c27595f9b1bfa67885015cb569ba2.1459397558.git.len.brown@intel.com> |
| X-Original-References | <1459397635-4871-1-git-send-email-lenb@kernel.org> |
| X-Original-Sender | linux-kernel-owner@vger.kernel.org |
| Xref | csiph.com linux.kernel:1367804 |
Show key headers only | View raw
From: Bin Gao <bin.gao@intel.com>
Hard code the BXT crystal clock (aka ART - Always Running Timer)
to 19.200 MHz, and use CPUID leaf 0x15 to determine the BXT TSC frequency.
Use tsc_khz to sanity check BXT cpu_khz,
which can be erroneous in some configurations.
Signed-off-by: Bin Gao <bin.gao@intel.com>
[lenb: simplified]
Signed-off-by: Len Brown <len.brown@intel.com>
---
arch/x86/kernel/tsc.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index ca41c30..64dc998 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -693,7 +693,11 @@ unsigned long native_calibrate_tsc(void)
switch (boot_cpu_data.x86_model) {
case 0x4E: /* SKL */
case 0x5E: /* SKL */
- crystal_khz = 24000; /* 24 MHz */
+ crystal_khz = 24000; /* 24.0 MHz */
+ break;
+ case 0x5C: /* BXT */
+ crystal_khz = 19200; /* 19.2 MHz */
+ break;
}
}
@@ -891,8 +895,12 @@ int recalibrate_cpu_khz(void)
if (cpu_has_tsc) {
cpu_khz = x86_platform.calibrate_cpu();
tsc_khz = x86_platform.calibrate_tsc();
+
if (tsc_khz == 0)
tsc_khz = cpu_khz;
+ else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
+ cpu_khz = tsc_khz;
+
cpu_data(0).loops_per_jiffy =
cpufreq_scale(cpu_data(0).loops_per_jiffy,
cpu_khz_old, cpu_khz);
@@ -1305,8 +1313,16 @@ void __init tsc_init(void)
cpu_khz = x86_platform.calibrate_cpu();
tsc_khz = x86_platform.calibrate_tsc();
+
+ /*
+ * Trust non-zero tsc_khz as authorative,
+ * and use it to sanity check cpu_khz,
+ * which will be off if system timer is off.
+ */
if (tsc_khz == 0)
tsc_khz = cpu_khz;
+ else if (abs(cpu_khz - tsc_khz) * 10 > tsc_khz)
+ cpu_khz = tsc_khz;
if (!tsc_khz) {
mark_tsc_unstable("could not calculate TSC khz");
--
2.8.0.rc4.16.g56331f8
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH 0/9] x86: TSC calibration update Len Brown <lenb@kernel.org> - 2016-03-31 06:20 +0200 [PATCH 6/9] x86 tsc_msr: Extend to include Intel Core Architecture Len Brown <lenb@kernel.org> - 2016-03-31 06:20 +0200 [PATCH 2/9] x86 tsc_msr: Remove debugging messages Len Brown <lenb@kernel.org> - 2016-03-31 06:20 +0200 [PATCH 9/9] x86 tsc: enumerate BXT tsc_khz via CPUID Len Brown <lenb@kernel.org> - 2016-03-31 06:20 +0200 [PATCH 4/9] x86 tsc_msr: Correct Silvermont reference clock values Len Brown <lenb@kernel.org> - 2016-03-31 06:20 +0200 [PATCH 5/9] x86 tsc_msr: Add Airmont reference clock values Len Brown <lenb@kernel.org> - 2016-03-31 06:20 +0200
csiph-web