[PATCH] rtc: armada38x: Align RTC set time procedure with the official errata
From: Gregory CLEMENT <hidden>
Date: 2015-08-06 15:18:48
Also in:
linux-rtc
Subsystem:
arm/marvell kirkwood and armada 370, 375, 38x, 39x, xp, 3700, 7k/8k, cn9130 soc support, real time clock (rtc) subsystem, the rest · Maintainers:
Andrew Lunn, Gregory Clement, Sebastian Hesselbarth, Alexandre Belloni, Linus Torvalds
From: Nadav Haklai <redacted> According to the Armada38x functional errata FE-3124064, writing to the RTC TIME register may fail. As a workaround, after writing to RTC TIME register, issue a dummy write of 0x0 twice to the RTC Status register. This is the updated implementation of the Errata that eliminates the need of the long 100ms delay during the RTC set time procedure. [gregory.clement at free-electrons.com]: removed the mutex and use the spinlock again Signed-off-by: Nadav Haklai <redacted> Reviewed-by: Neta Zur Hershkovits <redacted> Signed-off-by: Gregory CLEMENT <redacted> --- Hi, Finally the long 100ms wait was not needed! So we can remove the mutex introduced in an earlier commit. It would be great if this patch could be part of the 4.2-rc. Thanks Gregory drivers/rtc/rtc-armada38x.c | 32 ++++++++++++-------------------- 1 file changed, 12 insertions(+), 20 deletions(-)
diff --git a/drivers/rtc/rtc-armada38x.c b/drivers/rtc/rtc-armada38x.c
index 2b08cac62f07..06c6bd5eab41 100644
--- a/drivers/rtc/rtc-armada38x.c
+++ b/drivers/rtc/rtc-armada38x.c@@ -40,13 +40,6 @@ struct armada38x_rtc { void __iomem *regs; void __iomem *regs_soc; spinlock_t lock; - /* - * While setting the time, the RTC TIME register should not be - * accessed. Setting the RTC time involves sleeping during - * 100ms, so a mutex instead of a spinlock is used to protect - * it - */ - struct mutex mutex_time; int irq; };
@@ -64,9 +57,9 @@ static void rtc_delayed_write(u32 val, struct armada38x_rtc *rtc, int offset) static int armada38x_rtc_read_time(struct device *dev, struct rtc_time *tm) { struct armada38x_rtc *rtc = dev_get_drvdata(dev); - unsigned long time, time_check; + unsigned long time, time_check, flags; - mutex_lock(&rtc->mutex_time); + spin_lock_irqsave(&rtc->lock, flags); time = readl(rtc->regs + RTC_TIME); /* * WA for failing time set attempts. As stated in HW ERRATA if
@@ -77,7 +70,7 @@ static int armada38x_rtc_read_time(struct device *dev, struct rtc_time *tm) if ((time_check - time) > 1) time_check = readl(rtc->regs + RTC_TIME); - mutex_unlock(&rtc->mutex_time); + spin_unlock_irqrestore(&rtc->lock, flags); rtc_time_to_tm(time_check, tm);
@@ -88,23 +81,23 @@ static int armada38x_rtc_set_time(struct device *dev, struct rtc_time *tm) { struct armada38x_rtc *rtc = dev_get_drvdata(dev); int ret = 0; - unsigned long time; + unsigned long time, flags; ret = rtc_tm_to_time(tm, &time); if (ret) goto out; /* - * Setting the RTC time not always succeeds. According to the - * errata we need to first write on the status register and - * then wait for 100ms before writing to the time register to be - * sure that the data will be taken into account. + * According to errata FE-3124064, Write to RTC TIME register + * may fail. As a workaround, after writing to RTC TIME + * register, issue a dummy write of 0x0 twice to RTC Status + * register. */ - mutex_lock(&rtc->mutex_time); - rtc_delayed_write(0, rtc, RTC_STATUS); - msleep(100); + spin_lock_irqsave(&rtc->lock, flags); rtc_delayed_write(time, rtc, RTC_TIME); - mutex_unlock(&rtc->mutex_time); + rtc_delayed_write(0, rtc, RTC_STATUS); + rtc_delayed_write(0, rtc, RTC_STATUS); + spin_unlock_irqrestore(&rtc->lock, flags); out: return ret;
@@ -229,7 +222,6 @@ static __init int armada38x_rtc_probe(struct platform_device *pdev) return -ENOMEM; spin_lock_init(&rtc->lock); - mutex_init(&rtc->mutex_time); res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "rtc"); rtc->regs = devm_ioremap_resource(&pdev->dev, res);
--
2.1.0