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Patch "rtc: omap: Fix selecting external osc" has been added to the 4.8-stable tree

PATCH [email protected] 1 participant 1 message Nov 21, 2016

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Stable branch Real time clock (RTC)
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This is a note to let you know that I've just added the patch titled

rtc: omap: Fix selecting external osc

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
rtc-omap-fix-selecting-external-osc.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From 3984903a2e3906d3def220e688040ce93368200a Mon Sep 17 00:00:00 2001

From: Lokesh Vutla <[email protected]>
Date: Thu, 27 Oct 2016 11:27:25 +0530
Subject: rtc: omap: Fix selecting external osc

From: Lokesh Vutla <[email protected]>

commit 3984903a2e3906d3def220e688040ce93368200a upstream.

RTC can be clocked from an external 32KHz oscillator, or from the Peripheral PLL. The RTC has an internal oscillator buffer to support direct operation with a crystal.

            ----------------------------------------
            |       Device          ---------       |
            |                       |       |       |
            |                       | RTCSS |       |
            |       ---------       |       |       |
    OSC     |<------| RTC   |       |       |       |
            |------>| OSC   |---    |       |       |
            |       --------   |    |       |       |
            |                   ----|clk    |       |
            |       --------   |    |       |       |
            |       | PRCM  |---    |       |       |
            |       --------        --------        |
            ----------------------------------------

The RTC functional clock is sourced by default from the clock derived from the Peripheral PLL. In order to select source as external osc clk the following changes needs to be done:
- Enable the RTC OSC (RTC_OSC_REG[4]OSC32K_GZ = 0)
- Enable the clock mux(RTC_OSC_REG[6]K32CLK_EN = 1)
- Select the external clock source (RTC_OSC_REG[3]32KCLK_SEL = 1)

Fixes 399cf0f63f6f2 ("rtc: omap: Add external clock enabling support")
Signed-off-by Keerthy <[email protected]>
Signed-off-by Lokesh Vutla <[email protected]>
Signed-off-by Dave Gerlach <[email protected]>
Signed-off-by Alexandre Belloni <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/rtc/rtc-omap.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
drivers/rtc/rtc-omap.c +4 -2
@@ -109,6 +109,7 @@
 /* OMAP_RTC_OSC_REG bit fields: */
 #define OMAP_RTC_OSC_32KCLK_EN		BIT(6)
 #define OMAP_RTC_OSC_SEL_32KCLK_SRC	BIT(3)
+#define OMAP_RTC_OSC_OSC32K_GZ_DISABLE	BIT(4)
 
 /* OMAP_RTC_IRQWAKEEN bit fields: */
 #define OMAP_RTC_IRQWAKEEN_ALARM_WAKEEN	BIT(1)

@@ -646,8 +647,9 @@ static int omap_rtc_probe(struct platfor
 	 */
 	if (rtc->has_ext_clk) {
 		reg = rtc_read(rtc, OMAP_RTC_OSC_REG);
-		rtc_write(rtc, OMAP_RTC_OSC_REG,
-			  reg | OMAP_RTC_OSC_SEL_32KCLK_SRC);
+		reg &= ~OMAP_RTC_OSC_OSC32K_GZ_DISABLE;
+		reg |= OMAP_RTC_OSC_32KCLK_EN | OMAP_RTC_OSC_SEL_32KCLK_SRC;
+		rtc_writel(rtc, OMAP_RTC_OSC_REG, reg);
 	}
 
 	rtc->type->lock(rtc);

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/rtc-omap-fix-selecting-external-osc.patch