2020-07-30 10:04:57

by Dilip Kota

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 <[email protected]>
---
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

2020-07-31 08:47:54

by Andy Shevchenko

Subject: Re: [PATCH v2 1/1] x86/tsr: Fix tsc frequency enumeration failure on Lightning Mountain SoC

On Thu, Jul 30, 2020 at 1:01 PM Dilip Kota <[email protected]> wrote:
>
> 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.
>

I'm wondering if you get Tony's blessing for this change...
In any case, one nit-pick below and Cc Tony for the next version.

FWIW,
Reviewed-by: Andy Shevchenko <[email protected]>

> 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 <[email protected]>



> ---
> 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 },

Keep 8 per line (or 4 per line).

> .mask = 0x0f,
> };
>
> --
> 2.11.0
>


--
With Best Regards,
Andy Shevchenko