linux-kernel - [PATCH v2 1/1] x86/tsr: Fix tsc frequency enumeration failure on Lightning Mountain SoC

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Message-Id: <8b64c9f9e54351d841daea663f0579de3c103f15.1596103176.git.eswara.kota@linux.intel.com>
Date:   Thu, 30 Jul 2020 18:01:07 +0800
From:   Dilip Kota <eswara.kota@...ux.intel.com>
To:     x86@...nel.org, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        hpa@...or.com, rahul.tanwar@...ux.intel.com
Cc:     hdegoede@...hat.com, linux-kernel@...r.kernel.org,
        andy@...radead.org, cheol.yong.kim@...el.com,
        chuanhua.lei@...ux.intel.com, qi-ming.wu@...el.com,
        Dilip Kota <eswara.kota@...ux.intel.com>
Subject: [PATCH v2 1/1] x86/tsr: Fix tsc frequency enumeration failure on Lightning Mountain SoC

Frequency descriptor of Lightning Mountain SoC doesn't have all the
frequency entries so resulting in the below failure causing kernel hang.

[    0.000000] Error MSR_FSB_FREQ index 15 is unknown
[    0.000000] tsc: Fast TSC calibration failed

So, add all the frequency entries in the Lightning Mountain SoC frequency
descriptor.

Fixes: 0cc5359d8fd45 ("x86/cpu: Update init data for new Airmont CPU model")
Fixes: 812c2d7506fd ("x86/tsc_msr: Use named struct initializers")
Signed-off-by: Dilip Kota <eswara.kota@...ux.intel.com>
---
Changes on v2:
  Add description in the comments explaining about frequency entries.

 arch/x86/kernel/tsc_msr.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/tsc_msr.c b/arch/x86/kernel/tsc_msr.c
index 4fec6f3a1858b2..83b54c65aad2f3 100644
--- a/arch/x86/kernel/tsc_msr.c
+++ b/arch/x86/kernel/tsc_msr.c
@@ -133,10 +133,15 @@ static const struct freq_desc freq_desc_ann = {
 	.mask = 0x0f,
 };
 
-/* 24 MHz crystal? : 24 * 13 / 4 = 78 MHz */
+/*
+ * 24 MHz crystal? : 24 * 13 / 4 = 78 MHz
+ * Frequency step for Lightning Mountain SoC is fixed to 78 MHz,
+ * so all the frequency entries are 78000.
+ */
 static const struct freq_desc freq_desc_lgm = {
 	.use_msr_plat = true,
-	.freqs = { 78000, 78000, 78000, 78000, 78000, 78000, 78000, 78000 },
+	.freqs = { 78000, 78000, 78000, 78000, 78000, 78000, 78000, 78000, 78000,
+		   78000, 78000, 78000, 78000, 78000, 78000, 78000 },
 	.mask = 0x0f,
 };
 
-- 
2.11.0