[U-Boot] [PATCH 2/3] x86: Allow a hardcoded TSC frequency provided by Kconfig

[Bin Meng]

Hi Simon,

On Sun, Jan 4, 2015 at 10:31 AM, Simon Glass <sjg at chromium.org> wrote:
> Hi Bin,
>
> On 3 January 2015 at 07:40, Bin Meng <bmeng.cn at gmail.com> wrote:
>> By default U-Boot automatically calibrates TSC running frequency via
>> MSR and PIT. The calibration may not work on every x86 processor, so
>> a new Kconfig option CONFIG_TSC_CALIBRATION_BYPASS is introduced to
>> allow bypassing the calibration and assign a hardcoded TSC frequency
>> CONFIG_TSC_FREQ_IN_MHZ.
>>
>> Normally the bypass should be turned on in a simulation environment
>> like qemu.
>>
>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>
> Acked-by: Simon Glass <sjg at chromium.org>
>
> But see my optional thoughts below.
>
>> ---
>>
>>  arch/x86/Kconfig         | 18 ++++++++++++++++++
>>  arch/x86/lib/tsc_timer.c |  8 ++++++--
>>  2 files changed, 24 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index ebf72b3..9c11f0e 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -317,6 +317,24 @@ config FRAMEBUFFER_VESA_MODE
>>
>>  endmenu
>>
>> +config TSC_CALIBRATION_BYPASS
>> +       bool "Bypass TSC calibration"
>> +       default n
>> +       help
>> +         By default U-Boot automatically calibrates TSC running frequency via
>> +         MSR and PIT. If the calibration does not work on your board, select
>> +         this option and provide a hardcoded TSC running frequency below.
>
> Do you think TSC, MSR and PIT should be spelled out in the help? I
> worry that people won't make much sense of this. For example, if PIT
> is Platform Independent Timer we could save 'Platform Independent
> Timer (PIT)'.

Yes, a good idea. I can respin a v2 patch.

Regards,
Bin