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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Jinke Fan <fanjinke@hygon.cn>,
	Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>,
	Raul E Rangel <rrangel@chromium.org>,
	Mario Limonciello <mario.limonciello@amd.com>,
	Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.10 23/97] rtc: mc146818-lib: Fix the AltCentury for AMD platforms
Date: Mon, 23 May 2022 19:05:27 +0200	[thread overview]
Message-ID: <20220523165815.913462426@linuxfoundation.org> (raw)
In-Reply-To: <20220523165812.244140613@linuxfoundation.org>

From: Mario Limonciello <mario.limonciello@amd.com>

[ Upstream commit 3ae8fd41573af4fb3a490c9ed947fc936ba87190 ]

Setting the century forward has been failing on AMD platforms.
There was a previous attempt at fixing this for family 0x17 as part of
commit 7ad295d5196a ("rtc: Fix the AltCentury value on AMD/Hygon
platform") but this was later reverted due to some problems reported
that appeared to stem from an FW bug on a family 0x17 desktop system.

The same comments mentioned in the previous commit continue to apply
to the newer platforms as well.

```
MC146818 driver use function mc146818_set_time() to set register
RTC_FREQ_SELECT(RTC_REG_A)'s bit4-bit6 field which means divider stage
reset value on Intel platform to 0x7.

While AMD/Hygon RTC_REG_A(0Ah)'s bit4 is defined as DV0 [Reference]:
DV0 = 0 selects Bank 0, DV0 = 1 selects Bank 1. Bit5-bit6 is defined
as reserved.

DV0 is set to 1, it will select Bank 1, which will disable AltCentury
register(0x32) access. As UEFI pass acpi_gbl_FADT.century 0x32
(AltCentury), the CMOS write will be failed on code:
CMOS_WRITE(century, acpi_gbl_FADT.century).

Correct RTC_REG_A bank select bit(DV0) to 0 on AMD/Hygon CPUs, it will
enable AltCentury(0x32) register writing and finally setup century as
expected.
```

However in closer examination the change previously submitted was also
modifying bits 5 & 6 which are declared reserved in the AMD documentation.
So instead modify just the DV0 bank selection bit.

Being cognizant that there was a failure reported before, split the code
change out to a static function that can also be used for exclusions if
any regressions such as Mikhail's pop up again.

Cc: Jinke Fan <fanjinke@hygon.cn>
Cc: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Link: https://lore.kernel.org/all/CABXGCsMLob0DC25JS8wwAYydnDoHBSoMh2_YLPfqm3TTvDE-Zw@mail.gmail.com/
Link: https://www.amd.com/system/files/TechDocs/51192_Bolton_FCH_RRG.pdf
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220111225750.1699-1-mario.limonciello@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/rtc/rtc-mc146818-lib.c | 16 +++++++++++++++-
 include/linux/mc146818rtc.h    |  2 ++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c
index 5add637c9ad2..b036ff33fbe6 100644
--- a/drivers/rtc/rtc-mc146818-lib.c
+++ b/drivers/rtc/rtc-mc146818-lib.c
@@ -99,6 +99,17 @@ unsigned int mc146818_get_time(struct rtc_time *time)
 }
 EXPORT_SYMBOL_GPL(mc146818_get_time);
 
+/* AMD systems don't allow access to AltCentury with DV1 */
+static bool apply_amd_register_a_behavior(void)
+{
+#ifdef CONFIG_X86
+	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
+	    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
+		return true;
+#endif
+	return false;
+}
+
 /* Set the current date and time in the real time clock. */
 int mc146818_set_time(struct rtc_time *time)
 {
@@ -172,7 +183,10 @@ int mc146818_set_time(struct rtc_time *time)
 	save_control = CMOS_READ(RTC_CONTROL);
 	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
 	save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
-	CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
+	if (apply_amd_register_a_behavior())
+		CMOS_WRITE((save_freq_select & ~RTC_AMD_BANK_SELECT), RTC_FREQ_SELECT);
+	else
+		CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
 
 #ifdef CONFIG_MACH_DECSTATION
 	CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h
index 0661af17a758..1e0205811394 100644
--- a/include/linux/mc146818rtc.h
+++ b/include/linux/mc146818rtc.h
@@ -86,6 +86,8 @@ struct cmos_rtc_board_info {
    /* 2 values for divider stage reset, others for "testing purposes only" */
 #  define RTC_DIV_RESET1	0x60
 #  define RTC_DIV_RESET2	0x70
+   /* In AMD BKDG bit 5 and 6 are reserved, bit 4 is for select dv0 bank */
+#  define RTC_AMD_BANK_SELECT	0x10
   /* Periodic intr. / Square wave rate select. 0=none, 1=32.8kHz,... 15=2Hz */
 # define RTC_RATE_SELECT 	0x0F
 
-- 
2.35.1




  parent reply	other threads:[~2022-05-23 17:19 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-23 17:05 [PATCH 5.10 00/97] 5.10.118-rc1 review Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 01/97] usb: gadget: fix race when gadget driver register via ioctl Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 02/97] io_uring: always grab file table for deferred statx Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 03/97] floppy: use a statically allocated error counter Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 04/97] Revert "drm/i915/opregion: check port number bounds for SWSCI display power state" Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 05/97] igc: Remove _I_PHY_ID checking Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 06/97] igc: Remove phy->type checking Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 07/97] igc: Update I226_K device ID Greg Kroah-Hartman
2022-05-25 10:45   ` Pavel Machek
2022-05-26  4:02     ` Neftin, Sasha
2022-05-23 17:05 ` [PATCH 5.10 08/97] rtc: fix use-after-free on device removal Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 09/97] rtc: pcf2127: fix bug when reading alarm registers Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 10/97] um: Cleanup syscall_handler_t definition/cast, fix warning Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 11/97] Input: add bounds checking to input_set_capability() Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 12/97] Input: stmfts - fix reference leak in stmfts_input_open Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 13/97] nvme-pci: add quirks for Samsung X5 SSDs Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 14/97] gfs2: Disable page faults during lockless buffered reads Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 15/97] rtc: sun6i: Fix time overflow handling Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 16/97] crypto: stm32 - fix reference leak in stm32_crc_remove Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 17/97] crypto: x86/chacha20 - Avoid spurious jumps to other functions Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 18/97] ALSA: hda/realtek: Enable headset mic on Lenovo P360 Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 19/97] s390/pci: improve zpci_dev reference counting Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 20/97] vhost_vdpa: dont setup irq offloading when irq_num < 0 Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 21/97] tools/virtio: compile with -pthread Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 22/97] nvme-multipath: fix hang when disk goes live over reconnect Greg Kroah-Hartman
2022-05-23 17:05 ` Greg Kroah-Hartman [this message]
2022-05-23 17:05 ` [PATCH 5.10 24/97] fs: fix an infinite loop in iomap_fiemap Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 25/97] MIPS: lantiq: check the return value of kzalloc() Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 26/97] drbd: remove usage of list iterator variable after loop Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 27/97] platform/chrome: cros_ec_debugfs: detach log reader wq from devm Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 28/97] ARM: 9191/1: arm/stacktrace, kasan: Silence KASAN warnings in unwind_frame() Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 29/97] nilfs2: fix lockdep warnings in page operations for btree nodes Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 30/97] nilfs2: fix lockdep warnings during disk space reclamation Greg Kroah-Hartman
2022-05-23 17:05 ` [PATCH 5.10 31/97] Revert "swiotlb: fix info leak with DMA_FROM_DEVICE" Greg Kroah-Hartman
2022-05-23 18:25 ` [PATCH 5.10 00/97] 5.10.118-rc1 review Florian Fainelli
2022-05-23 21:36 ` Daniel Díaz
2022-05-25  7:16   ` Greg Kroah-Hartman
2022-05-23 22:56 ` Shuah Khan
2022-05-24  9:24 ` Fox Chen
2022-05-24 14:49 ` Sudip Mukherjee
2022-05-24 15:25 ` Pavel Machek
2022-05-24 20:04 ` Guenter Roeck
2022-05-25  1:05 ` Samuel Zou

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