linux/drivers/rtc/rtc-snvs.c
Stefan Eichenberger 0462681e20 rtc: snvs: Allow a time difference on clock register read
On an iMX6ULL the following message appears when a wakealarm is set:

echo 0 > /sys/class/rtc/rtc1/wakealarm
rtc rtc1: Timeout trying to get valid LPSRT Counter read

This does not always happen but is reproducible quite often (7 out of 10
times). The problem appears because the iMX6ULL is not able to read the
registers within one 32kHz clock cycle which is the base clock of the
RTC. Therefore, this patch allows a difference of up to 320 cycles
(10ms). 10ms was chosen to be big enough even on systems with less cpu
power (e.g. iMX6ULL). According to the reference manual a difference is
fine:
- If the two consecutive reads are similar, the value is correct.
The values have to be similar, not equal.

Fixes: cd7f3a249d ("rtc: snvs: Add timeouts to avoid kernel lockups")
Reviewed-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Signed-off-by: Stefan Eichenberger <stefan.eichenberger@toradex.com>
Signed-off-by: Francesco Dolcini <francesco@dolcini.it>
Link: https://lore.kernel.org/r/20221106115915.7930-1-francesco@dolcini.it
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
2022-11-15 21:25:44 +01:00

447 lines
11 KiB
C

// SPDX-License-Identifier: GPL-2.0+
//
// Copyright (C) 2011-2012 Freescale Semiconductor, Inc.
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_wakeirq.h>
#include <linux/rtc.h>
#include <linux/clk.h>
#include <linux/mfd/syscon.h>
#include <linux/regmap.h>
#define SNVS_LPREGISTER_OFFSET 0x34
/* These register offsets are relative to LP (Low Power) range */
#define SNVS_LPCR 0x04
#define SNVS_LPSR 0x18
#define SNVS_LPSRTCMR 0x1c
#define SNVS_LPSRTCLR 0x20
#define SNVS_LPTAR 0x24
#define SNVS_LPPGDR 0x30
#define SNVS_LPCR_SRTC_ENV (1 << 0)
#define SNVS_LPCR_LPTA_EN (1 << 1)
#define SNVS_LPCR_LPWUI_EN (1 << 3)
#define SNVS_LPSR_LPTA (1 << 0)
#define SNVS_LPPGDR_INIT 0x41736166
#define CNTR_TO_SECS_SH 15
/* The maximum RTC clock cycles that are allowed to pass between two
* consecutive clock counter register reads. If the values are corrupted a
* bigger difference is expected. The RTC frequency is 32kHz. With 320 cycles
* we end at 10ms which should be enough for most cases. If it once takes
* longer than expected we do a retry.
*/
#define MAX_RTC_READ_DIFF_CYCLES 320
struct snvs_rtc_data {
struct rtc_device *rtc;
struct regmap *regmap;
int offset;
int irq;
struct clk *clk;
};
/* Read 64 bit timer register, which could be in inconsistent state */
static u64 rtc_read_lpsrt(struct snvs_rtc_data *data)
{
u32 msb, lsb;
regmap_read(data->regmap, data->offset + SNVS_LPSRTCMR, &msb);
regmap_read(data->regmap, data->offset + SNVS_LPSRTCLR, &lsb);
return (u64)msb << 32 | lsb;
}
/* Read the secure real time counter, taking care to deal with the cases of the
* counter updating while being read.
*/
static u32 rtc_read_lp_counter(struct snvs_rtc_data *data)
{
u64 read1, read2;
s64 diff;
unsigned int timeout = 100;
/* As expected, the registers might update between the read of the LSB
* reg and the MSB reg. It's also possible that one register might be
* in partially modified state as well.
*/
read1 = rtc_read_lpsrt(data);
do {
read2 = read1;
read1 = rtc_read_lpsrt(data);
diff = read1 - read2;
} while (((diff < 0) || (diff > MAX_RTC_READ_DIFF_CYCLES)) && --timeout);
if (!timeout)
dev_err(&data->rtc->dev, "Timeout trying to get valid LPSRT Counter read\n");
/* Convert 47-bit counter to 32-bit raw second count */
return (u32) (read1 >> CNTR_TO_SECS_SH);
}
/* Just read the lsb from the counter, dealing with inconsistent state */
static int rtc_read_lp_counter_lsb(struct snvs_rtc_data *data, u32 *lsb)
{
u32 count1, count2;
s32 diff;
unsigned int timeout = 100;
regmap_read(data->regmap, data->offset + SNVS_LPSRTCLR, &count1);
do {
count2 = count1;
regmap_read(data->regmap, data->offset + SNVS_LPSRTCLR, &count1);
diff = count1 - count2;
} while (((diff < 0) || (diff > MAX_RTC_READ_DIFF_CYCLES)) && --timeout);
if (!timeout) {
dev_err(&data->rtc->dev, "Timeout trying to get valid LPSRT Counter read\n");
return -ETIMEDOUT;
}
*lsb = count1;
return 0;
}
static int rtc_write_sync_lp(struct snvs_rtc_data *data)
{
u32 count1, count2;
u32 elapsed;
unsigned int timeout = 1000;
int ret;
ret = rtc_read_lp_counter_lsb(data, &count1);
if (ret)
return ret;
/* Wait for 3 CKIL cycles, about 61.0-91.5 µs */
do {
ret = rtc_read_lp_counter_lsb(data, &count2);
if (ret)
return ret;
elapsed = count2 - count1; /* wrap around _is_ handled! */
} while (elapsed < 3 && --timeout);
if (!timeout) {
dev_err(&data->rtc->dev, "Timeout waiting for LPSRT Counter to change\n");
return -ETIMEDOUT;
}
return 0;
}
static int snvs_rtc_enable(struct snvs_rtc_data *data, bool enable)
{
int timeout = 1000;
u32 lpcr;
regmap_update_bits(data->regmap, data->offset + SNVS_LPCR, SNVS_LPCR_SRTC_ENV,
enable ? SNVS_LPCR_SRTC_ENV : 0);
while (--timeout) {
regmap_read(data->regmap, data->offset + SNVS_LPCR, &lpcr);
if (enable) {
if (lpcr & SNVS_LPCR_SRTC_ENV)
break;
} else {
if (!(lpcr & SNVS_LPCR_SRTC_ENV))
break;
}
}
if (!timeout)
return -ETIMEDOUT;
return 0;
}
static int snvs_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
struct snvs_rtc_data *data = dev_get_drvdata(dev);
unsigned long time;
int ret;
ret = clk_enable(data->clk);
if (ret)
return ret;
time = rtc_read_lp_counter(data);
rtc_time64_to_tm(time, tm);
clk_disable(data->clk);
return 0;
}
static int snvs_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
struct snvs_rtc_data *data = dev_get_drvdata(dev);
unsigned long time = rtc_tm_to_time64(tm);
int ret;
ret = clk_enable(data->clk);
if (ret)
return ret;
/* Disable RTC first */
ret = snvs_rtc_enable(data, false);
if (ret)
return ret;
/* Write 32-bit time to 47-bit timer, leaving 15 LSBs blank */
regmap_write(data->regmap, data->offset + SNVS_LPSRTCLR, time << CNTR_TO_SECS_SH);
regmap_write(data->regmap, data->offset + SNVS_LPSRTCMR, time >> (32 - CNTR_TO_SECS_SH));
/* Enable RTC again */
ret = snvs_rtc_enable(data, true);
clk_disable(data->clk);
return ret;
}
static int snvs_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct snvs_rtc_data *data = dev_get_drvdata(dev);
u32 lptar, lpsr;
int ret;
ret = clk_enable(data->clk);
if (ret)
return ret;
regmap_read(data->regmap, data->offset + SNVS_LPTAR, &lptar);
rtc_time64_to_tm(lptar, &alrm->time);
regmap_read(data->regmap, data->offset + SNVS_LPSR, &lpsr);
alrm->pending = (lpsr & SNVS_LPSR_LPTA) ? 1 : 0;
clk_disable(data->clk);
return 0;
}
static int snvs_rtc_alarm_irq_enable(struct device *dev, unsigned int enable)
{
struct snvs_rtc_data *data = dev_get_drvdata(dev);
int ret;
ret = clk_enable(data->clk);
if (ret)
return ret;
regmap_update_bits(data->regmap, data->offset + SNVS_LPCR,
(SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN),
enable ? (SNVS_LPCR_LPTA_EN | SNVS_LPCR_LPWUI_EN) : 0);
ret = rtc_write_sync_lp(data);
clk_disable(data->clk);
return ret;
}
static int snvs_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
{
struct snvs_rtc_data *data = dev_get_drvdata(dev);
unsigned long time = rtc_tm_to_time64(&alrm->time);
int ret;
ret = clk_enable(data->clk);
if (ret)
return ret;
regmap_update_bits(data->regmap, data->offset + SNVS_LPCR, SNVS_LPCR_LPTA_EN, 0);
ret = rtc_write_sync_lp(data);
if (ret)
return ret;
regmap_write(data->regmap, data->offset + SNVS_LPTAR, time);
/* Clear alarm interrupt status bit */
regmap_write(data->regmap, data->offset + SNVS_LPSR, SNVS_LPSR_LPTA);
clk_disable(data->clk);
return snvs_rtc_alarm_irq_enable(dev, alrm->enabled);
}
static const struct rtc_class_ops snvs_rtc_ops = {
.read_time = snvs_rtc_read_time,
.set_time = snvs_rtc_set_time,
.read_alarm = snvs_rtc_read_alarm,
.set_alarm = snvs_rtc_set_alarm,
.alarm_irq_enable = snvs_rtc_alarm_irq_enable,
};
static irqreturn_t snvs_rtc_irq_handler(int irq, void *dev_id)
{
struct device *dev = dev_id;
struct snvs_rtc_data *data = dev_get_drvdata(dev);
u32 lpsr;
u32 events = 0;
clk_enable(data->clk);
regmap_read(data->regmap, data->offset + SNVS_LPSR, &lpsr);
if (lpsr & SNVS_LPSR_LPTA) {
events |= (RTC_AF | RTC_IRQF);
/* RTC alarm should be one-shot */
snvs_rtc_alarm_irq_enable(dev, 0);
rtc_update_irq(data->rtc, 1, events);
}
/* clear interrupt status */
regmap_write(data->regmap, data->offset + SNVS_LPSR, lpsr);
clk_disable(data->clk);
return events ? IRQ_HANDLED : IRQ_NONE;
}
static const struct regmap_config snvs_rtc_config = {
.reg_bits = 32,
.val_bits = 32,
.reg_stride = 4,
};
static void snvs_rtc_action(void *data)
{
clk_disable_unprepare(data);
}
static int snvs_rtc_probe(struct platform_device *pdev)
{
struct snvs_rtc_data *data;
int ret;
void __iomem *mmio;
data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
if (!data)
return -ENOMEM;
data->rtc = devm_rtc_allocate_device(&pdev->dev);
if (IS_ERR(data->rtc))
return PTR_ERR(data->rtc);
data->regmap = syscon_regmap_lookup_by_phandle(pdev->dev.of_node, "regmap");
if (IS_ERR(data->regmap)) {
dev_warn(&pdev->dev, "snvs rtc: you use old dts file, please update it\n");
mmio = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(mmio))
return PTR_ERR(mmio);
data->regmap = devm_regmap_init_mmio(&pdev->dev, mmio, &snvs_rtc_config);
} else {
data->offset = SNVS_LPREGISTER_OFFSET;
of_property_read_u32(pdev->dev.of_node, "offset", &data->offset);
}
if (IS_ERR(data->regmap)) {
dev_err(&pdev->dev, "Can't find snvs syscon\n");
return -ENODEV;
}
data->irq = platform_get_irq(pdev, 0);
if (data->irq < 0)
return data->irq;
data->clk = devm_clk_get(&pdev->dev, "snvs-rtc");
if (IS_ERR(data->clk)) {
data->clk = NULL;
} else {
ret = clk_prepare_enable(data->clk);
if (ret) {
dev_err(&pdev->dev,
"Could not prepare or enable the snvs clock\n");
return ret;
}
}
ret = devm_add_action_or_reset(&pdev->dev, snvs_rtc_action, data->clk);
if (ret)
return ret;
platform_set_drvdata(pdev, data);
/* Initialize glitch detect */
regmap_write(data->regmap, data->offset + SNVS_LPPGDR, SNVS_LPPGDR_INIT);
/* Clear interrupt status */
regmap_write(data->regmap, data->offset + SNVS_LPSR, 0xffffffff);
/* Enable RTC */
ret = snvs_rtc_enable(data, true);
if (ret) {
dev_err(&pdev->dev, "failed to enable rtc %d\n", ret);
return ret;
}
device_init_wakeup(&pdev->dev, true);
ret = dev_pm_set_wake_irq(&pdev->dev, data->irq);
if (ret)
dev_err(&pdev->dev, "failed to enable irq wake\n");
ret = devm_request_irq(&pdev->dev, data->irq, snvs_rtc_irq_handler,
IRQF_SHARED, "rtc alarm", &pdev->dev);
if (ret) {
dev_err(&pdev->dev, "failed to request irq %d: %d\n",
data->irq, ret);
return ret;
}
data->rtc->ops = &snvs_rtc_ops;
data->rtc->range_max = U32_MAX;
return devm_rtc_register_device(data->rtc);
}
static int __maybe_unused snvs_rtc_suspend_noirq(struct device *dev)
{
struct snvs_rtc_data *data = dev_get_drvdata(dev);
clk_disable(data->clk);
return 0;
}
static int __maybe_unused snvs_rtc_resume_noirq(struct device *dev)
{
struct snvs_rtc_data *data = dev_get_drvdata(dev);
if (data->clk)
return clk_enable(data->clk);
return 0;
}
static const struct dev_pm_ops snvs_rtc_pm_ops = {
SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(snvs_rtc_suspend_noirq, snvs_rtc_resume_noirq)
};
static const struct of_device_id snvs_dt_ids[] = {
{ .compatible = "fsl,sec-v4.0-mon-rtc-lp", },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, snvs_dt_ids);
static struct platform_driver snvs_rtc_driver = {
.driver = {
.name = "snvs_rtc",
.pm = &snvs_rtc_pm_ops,
.of_match_table = snvs_dt_ids,
},
.probe = snvs_rtc_probe,
};
module_platform_driver(snvs_rtc_driver);
MODULE_AUTHOR("Freescale Semiconductor, Inc.");
MODULE_DESCRIPTION("Freescale SNVS RTC Driver");
MODULE_LICENSE("GPL");