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Tue, 28 Nov 2023 08:46:38 -0600 From: Mario Limonciello To: =?UTF-8?q?Mateusz=20Jo=C5=84czyk?= , Alessandro Zummo , Alexandre Belloni CC: "open list:REAL TIME CLOCK (RTC) SUBSYSTEM" , open list , , , , , , , , Dave Hansen , Borislav Petkov , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , Mario Limonciello Subject: [PATCH v4 3/4] rtc: Add support for configuring the UIP timeout for RTC reads Date: Mon, 27 Nov 2023 23:36:52 -0600 Message-ID: <20231128053653.101798-4-mario.limonciello@amd.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20231128053653.101798-1-mario.limonciello@amd.com> References: <20231128053653.101798-1-mario.limonciello@amd.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.180.168.240] X-ClientProxiedBy: SATLEXMB04.amd.com (10.181.40.145) To SATLEXMB04.amd.com (10.181.40.145) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF000042A7:EE_|DS0PR12MB6605:EE_ X-MS-Office365-Filtering-Correlation-Id: 50b24af6-af33-4a40-f804-08dbf020d713 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB04.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230031)(4636009)(346002)(396003)(39860400002)(136003)(376002)(230273577357003)(230173577357003)(230922051799003)(186009)(451199024)(64100799003)(82310400011)(1800799012)(46966006)(36840700001)(40470700004)(8676002)(6666004)(8936002)(45080400002)(4326008)(7696005)(316002)(70206006)(110136005)(70586007)(54906003)(40460700003)(478600001)(81166007)(47076005)(356005)(36756003)(41300700001)(1076003)(86362001)(26005)(40480700001)(2906002)(36860700001)(44832011)(2616005)(83380400001)(336012)(426003)(16526019)(5660300002)(82740400003)(7416002)(557034005)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 Nov 2023 14:46:43.9524 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 50b24af6-af33-4a40-f804-08dbf020d713 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1PEPF000042A7.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB6605 X-Spam-Status: No, score=0.2 required=5.0 tests=DATE_IN_PAST_06_12, DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on morse.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (morse.vger.email [0.0.0.0]); Tue, 28 Nov 2023 06:47:11 -0800 (PST) The UIP timeout is hardcoded to 10ms for all RTC reads, but in some contexts this might not be enough time. Add a timeout parameter to mc146818_get_time() and mc146818_get_time_callback(). If UIP timeout is configured by caller to be >=100 ms and a call takes this long, log a warning. Make all callers use 10ms to ensure no functional changes. Cc: stable@vger.kernel.org # 6.1.y Fixes: ec5895c0f2d8 ("rtc: mc146818-lib: extract mc146818_avoid_UIP") Signed-off-by: Mario Limonciello --- v3->v4: * Change label * Logic adjustment for for loop * Fix pr_warn variable v2->v3: * Logic adjustments * Clarify warning message v1->v2: * Add a warning if 100ms or more * Add stable and fixes tags --- arch/alpha/kernel/rtc.c | 2 +- arch/x86/kernel/hpet.c | 2 +- arch/x86/kernel/rtc.c | 2 +- drivers/base/power/trace.c | 2 +- drivers/rtc/rtc-cmos.c | 6 +++--- drivers/rtc/rtc-mc146818-lib.c | 37 ++++++++++++++++++++++++++-------- include/linux/mc146818rtc.h | 3 ++- 7 files changed, 38 insertions(+), 16 deletions(-) diff --git a/arch/alpha/kernel/rtc.c b/arch/alpha/kernel/rtc.c index fb3025396ac9..cfdf90bc8b3f 100644 --- a/arch/alpha/kernel/rtc.c +++ b/arch/alpha/kernel/rtc.c @@ -80,7 +80,7 @@ init_rtc_epoch(void) static int alpha_rtc_read_time(struct device *dev, struct rtc_time *tm) { - int ret = mc146818_get_time(tm); + int ret = mc146818_get_time(tm, 10); if (ret < 0) { dev_err_ratelimited(dev, "unable to read current time\n"); diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index 41eecf180b7f..17adad4cbe78 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -1438,7 +1438,7 @@ irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id) memset(&curr_time, 0, sizeof(struct rtc_time)); if (hpet_rtc_flags & (RTC_UIE | RTC_AIE)) { - if (unlikely(mc146818_get_time(&curr_time) < 0)) { + if (unlikely(mc146818_get_time(&curr_time, 10) < 0)) { pr_err_ratelimited("unable to read current time from RTC\n"); return IRQ_HANDLED; } diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c index 1309b9b05338..961ebc7f1872 100644 --- a/arch/x86/kernel/rtc.c +++ b/arch/x86/kernel/rtc.c @@ -67,7 +67,7 @@ void mach_get_cmos_time(struct timespec64 *now) return; } - if (mc146818_get_time(&tm)) { + if (mc146818_get_time(&tm, 10)) { pr_err("Unable to read current time from RTC\n"); now->tv_sec = now->tv_nsec = 0; return; diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c index 72b7a92337b1..c2e925357474 100644 --- a/drivers/base/power/trace.c +++ b/drivers/base/power/trace.c @@ -120,7 +120,7 @@ static unsigned int read_magic_time(void) struct rtc_time time; unsigned int val; - if (mc146818_get_time(&time) < 0) { + if (mc146818_get_time(&time, 10) < 0) { pr_err("Unable to read current time from RTC\n"); return 0; } diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c index 391f91d3d144..d278b085821e 100644 --- a/drivers/rtc/rtc-cmos.c +++ b/drivers/rtc/rtc-cmos.c @@ -231,7 +231,7 @@ static int cmos_read_time(struct device *dev, struct rtc_time *t) if (!pm_trace_rtc_valid()) return -EIO; - ret = mc146818_get_time(t); + ret = mc146818_get_time(t, 10); if (ret < 0) { dev_err_ratelimited(dev, "unable to read current time\n"); return ret; @@ -307,7 +307,7 @@ static int cmos_read_alarm(struct device *dev, struct rtc_wkalrm *t) * * Use the mc146818_avoid_UIP() function to avoid this. */ - if (!mc146818_avoid_UIP(cmos_read_alarm_callback, &p)) + if (!mc146818_avoid_UIP(cmos_read_alarm_callback, 10, &p)) return -EIO; if (!(p.rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { @@ -556,7 +556,7 @@ static int cmos_set_alarm(struct device *dev, struct rtc_wkalrm *t) * * Use mc146818_avoid_UIP() to avoid this. */ - if (!mc146818_avoid_UIP(cmos_set_alarm_callback, &p)) + if (!mc146818_avoid_UIP(cmos_set_alarm_callback, 10, &p)) return -ETIMEDOUT; cmos->alarm_expires = rtc_tm_to_time64(&t->time); diff --git a/drivers/rtc/rtc-mc146818-lib.c b/drivers/rtc/rtc-mc146818-lib.c index 43a28e82674e..4c17b3cef11e 100644 --- a/drivers/rtc/rtc-mc146818-lib.c +++ b/drivers/rtc/rtc-mc146818-lib.c @@ -8,26 +8,31 @@ #include #endif +#define UIP_RECHECK_DELAY 100 /* usec */ +#define UIP_RECHECK_DELAY_MS (USEC_PER_MSEC / UIP_RECHECK_DELAY) +#define UIP_RECHECK_LOOPS_MS(x) (x / UIP_RECHECK_DELAY_MS) + /* * Execute a function while the UIP (Update-in-progress) bit of the RTC is - * unset. + * unset. The timeout is configurable by the caller in ms. * * Warning: callback may be executed more then once. */ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param), + int timeout, void *param) { int i; unsigned long flags; unsigned char seconds; - for (i = 0; i < 100; i++) { + for (i = 0; UIP_RECHECK_LOOPS_MS(i) < timeout; i++) { spin_lock_irqsave(&rtc_lock, flags); /* * Check whether there is an update in progress during which the * readout is unspecified. The maximum update time is ~2ms. Poll - * every 100 usec for completion. + * for completion. * * Store the second value before checking UIP so a long lasting * NMI which happens to hit after the UIP check cannot make @@ -37,7 +42,7 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param), if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) { spin_unlock_irqrestore(&rtc_lock, flags); - udelay(100); + udelay(UIP_RECHECK_DELAY); continue; } @@ -56,7 +61,7 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param), */ if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) { spin_unlock_irqrestore(&rtc_lock, flags); - udelay(100); + udelay(UIP_RECHECK_DELAY); continue; } @@ -72,6 +77,10 @@ bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param), } spin_unlock_irqrestore(&rtc_lock, flags); + if (UIP_RECHECK_LOOPS_MS(i) >= 100) + pr_warn("Reading current time from RTC took around %li ms\n", + UIP_RECHECK_LOOPS_MS(i)); + return true; } return false; @@ -84,7 +93,7 @@ EXPORT_SYMBOL_GPL(mc146818_avoid_UIP); */ bool mc146818_does_rtc_work(void) { - return mc146818_avoid_UIP(NULL, NULL); + return mc146818_avoid_UIP(NULL, 10, NULL); } EXPORT_SYMBOL_GPL(mc146818_does_rtc_work); @@ -130,13 +139,25 @@ static void mc146818_get_time_callback(unsigned char seconds, void *param_in) p->ctrl = CMOS_READ(RTC_CONTROL); } -int mc146818_get_time(struct rtc_time *time) +/** + * mc146818_get_time - Get the current time from the RTC + * @time: pointer to struct rtc_time to store the current time + * @timeout: timeout value in ms + * + * This function reads the current time from the RTC and stores it in the + * provided struct rtc_time. The timeout parameter specifies the maximum + * time to wait for the RTC to become ready. + * + * Return: 0 on success, -ETIMEDOUT if the RTC did not become ready within + * the specified timeout, or another error code if an error occurred. + */ +int mc146818_get_time(struct rtc_time *time, int timeout) { struct mc146818_get_time_callback_param p = { .time = time }; - if (!mc146818_avoid_UIP(mc146818_get_time_callback, &p)) { + if (!mc146818_avoid_UIP(mc146818_get_time_callback, timeout, &p)) { memset(time, 0, sizeof(*time)); return -ETIMEDOUT; } diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h index b0da04fe087b..34dfcc77f505 100644 --- a/include/linux/mc146818rtc.h +++ b/include/linux/mc146818rtc.h @@ -126,10 +126,11 @@ struct cmos_rtc_board_info { #endif /* ARCH_RTC_LOCATION */ bool mc146818_does_rtc_work(void); -int mc146818_get_time(struct rtc_time *time); +int mc146818_get_time(struct rtc_time *time, int timeout); int mc146818_set_time(struct rtc_time *time); bool mc146818_avoid_UIP(void (*callback)(unsigned char seconds, void *param), + int timeout, void *param); #endif /* _MC146818RTC_H */ -- 2.34.1