On 22.05.2024 15:57, Jason Andryuk wrote:
> On 2024-05-22 08:59, Jan Beulich wrote:
>> --- a/xen/arch/x86/time.c
>> +++ b/xen/arch/x86/time.c
>> @@ -427,6 +427,74 @@ static struct platform_timesource __init
>> .resume = resume_pit,
>> };
>>
>> +unsigned int __initdata pit_alias_mask;
>> +
>> +static void __init probe_pit_alias(void)
>> +{
>> + unsigned int mask = 0x1c;
>> + uint8_t val = 0;
>> +
>> + if ( !opt_probe_port_aliases )
>> + return;
>> +
>> + /*
>> + * Use channel 2 in mode 0 for probing. In this mode even a non-initial
>> + * count is loaded independent of counting being / becoming enabled.
>> Thus
>> + * we have a 16-bit value fully under our control, to write and then
>> check
>> + * whether we can also read it back unaltered.
>> + */
>> +
>> + /* Turn off speaker output and disable channel 2 counting. */
>> + outb(inb(0x61) & 0x0c, 0x61);
>> +
>> + outb(PIT_LTCH_CH(2) | PIT_RW_LSB_MSB | PIT_MODE_EOC | PIT_BINARY,
>> + PIT_MODE);
>> +
>> + do {
>> + uint8_t val2;
>> + unsigned int offs;
>> +
>> + outb(val, PIT_CH2);
>> + outb(val ^ 0xff, PIT_CH2);
>> +
>> + /* Wait for the Null Count bit to clear. */
>> + do {
>> + /* Latch status. */
>> + outb(PIT_RDB | PIT_RDB_NO_COUNT | PIT_RDB_CH2, PIT_MODE);
>> +
>> + /* Try to make sure we're actually having a PIT here. */
>> + val2 = inb(PIT_CH2);
>> + if ( (val2 & ~(PIT_STATUS_OUT_PIN | PIT_STATUS_NULL_COUNT)) !=
>> + (PIT_RW_LSB_MSB | PIT_MODE_EOC | PIT_BINARY) )
>> + return;
>> + } while ( val2 & (1 << 6) );
>
> You can use PIT_STATUS_NULL_COUNT here.
Indeed, and I meant to but then forgot. Thanks for noticing.
> With that:
> Reviewed-by: Jason Andryuk <jason.andr...@amd.com>
Thanks.
Jan
