[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH for-4.22 1/5] x86/time: use RTC century byte when available
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 13 May 2026 17:08:29 +0200
- Authentication-results: eu.smtp.expurgate.cloud; dkim=pass header.s=google header.d=suse.com header.i="@suse.com" header.h="Content-Transfer-Encoding:In-Reply-To:Autocrypt:From:Content-Language:References:Cc:To:Subject:User-Agent:MIME-Version:Date:Message-ID"
- Autocrypt: addr=jbeulich@xxxxxxxx; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL
- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Teddy Astie <teddy.astie@xxxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
- Delivery-date: Wed, 13 May 2026 15:08:41 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 13.05.2026 16:51, Roger Pau Monné wrote:
> On Wed, May 13, 2026 at 12:36:26PM +0200, Jan Beulich wrote:
>> On 13.05.2026 10:49, Roger Pau Monné wrote:
>>> On Tue, May 12, 2026 at 04:58:43PM +0200, Jan Beulich wrote:
>>>> @@ -1280,6 +1281,8 @@ static bool __get_cmos_time(struct rtc_t
>>>> rtc->day = CMOS_READ(RTC_DAY_OF_MONTH);
>>>> rtc->mon = CMOS_READ(RTC_MONTH);
>>>> rtc->year = CMOS_READ(RTC_YEAR);
>>>> + if ( acpi_gbl_FADT.century && acpi_gbl_FADT.century < 0x80 )
>>>> + century = CMOS_READ(acpi_gbl_FADT.century);
>>>>
>>>> if ( RTC_ALWAYS_BCD || !(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) )
>>>> {
>>>> @@ -1293,7 +1296,12 @@ static bool __get_cmos_time(struct rtc_t
>>>>
>>>> spin_unlock_irqrestore(&rtc_lock, flags);
>>>>
>>>> - if ( (rtc->year += 1900) < 1970 )
>>>> + if ( century )
>>>> + {
>>>> + BCD_TO_BIN(century);
>>>
>>> Don't you need to move the BCD_TO_BIN() translation with the rest, so
>>> it's not done unconditionally?
>>
>> No, the century field is always BCD.
>
> Hm, then I guess Linux needs adjusting, as mc146818_set_time() only
> converts the century to the BCD format conditionally on the control
> register or RTC_ALWAYS_BCD.
Hmm, indeed.
Btw, while looking there I also noticed this
#ifdef CONFIG_ACPI
if (p.century > 19)
time->tm_year += (p.century - 19) * 100;
#endif
(relevant to a remark you gave on a later patch in this series).
> I've found several sources only that as you mention also claim the
> century value is unconditionally in BCD format.
>
> Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Thanks.
Jan
|
