Hi,
On 01/25/2017 05:23 PM, Ingo Molnar wrote:
> * Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
>
>>> Hiding essentially an early udelay() implementation in an early-printk driver is
>>> ugly and counterproductive.
>> Sure. How about below change?
>>
>> diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
>> index d3f0c84..940989e 100644
>> --- a/drivers/usb/early/xhci-dbc.c
>> +++ b/drivers/usb/early/xhci-dbc.c
>> @@ -587,6 +587,35 @@ static int xdbc_bulk_transfer(void *data, int size, bool read)
>> return size;
>> }
>>
>> +static void __init xdbc_udelay_calibration(void)
>> +{
>> + unsigned long lpj = 0;
>> + unsigned int tsc_khz, cpu_khz;
>> +
>> + if (!boot_cpu_has(X86_FEATURE_TSC))
>> + goto calibration_out;
>> +
>> + 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;
>> +
>> + if (!tsc_khz)
>> + goto calibration_out;
>> +
>> + lpj = tsc_khz * 1000;
>> + do_div(lpj, HZ);
>> +
>> +calibration_out:
>> + if (!lpj)
>> + lpj = 1 << 22;
>> +
>> + loops_per_jiffy = lpj;
>> +}
>> +
>> static int __init xdbc_early_setup(void)
>> {
>> int ret;
>> @@ -686,6 +715,8 @@ int __init early_xdbc_parse_parameter(char *s)
>> }
>> xdbc.xdbc_reg = (struct xdbc_regs __iomem *)(xdbc.xhci_base + offset);
>>
>> + xdbc_udelay_calibration();
>> +
>> return 0;
>> }
> Yeah - so could we do this in a more generic fashion, not in the early-printk
> driver but in core x86 code?
>
Sure. I will move this to arch/x86/kernel/setup.c.
Best regards,
Lu Baolu
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