This is a note to let you know that I have just added a patch titled
MIPS: Malta: Don't reinitialise RTC
to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue
This patch is scheduled to be released in version 3.19.8-ckt7.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
------
>From 5b7fde3e398317f122726a5e6f8f603717d263a2 Mon Sep 17 00:00:00 2001
From: James Hogan <james.hogan@xxxxxxxxxx>
Date: Fri, 17 Jul 2015 15:54:41 +0100
Subject: MIPS: Malta: Don't reinitialise RTC
commit 106eccb4d20f35ebc58ff2286c170d9e79c5ff68 upstream.
On Malta, since commit a87ea88d8f6c ("MIPS: Malta: initialise the RTC at
boot"), the RTC is reinitialised and forced into binary coded decimal
(BCD) mode during init, even if the bootloader has already initialised
it, and may even have already put it into binary mode (as YAMON does).
This corrupts the current time, can result in the RTC seconds being an
invalid BCD (e.g. 0x1a..0x1f) for up to 6 seconds, as well as confusing
YAMON for a while after reset, enough for it to report timeouts when
attempting to load from TFTP (it actually uses the RTC in that code).
Therefore only initialise the RTC to the extent that is necessary so
that Linux avoids interfering with the bootloader setup, while also
allowing it to estimate the CPU frequency without hanging, without a
bootloader necessarily having done anything with the RTC (for example
when the kernel is loaded via EJTAG).
The divider control is configured for a 32KHZ reference clock if
necessary, and the SET bit of the RTC_CONTROL register is cleared if
necessary without changing any other bits (this bit will be set when
coming out of reset if the battery has been disconnected).
Fixes: a87ea88d8f6c ("MIPS: Malta: initialise the RTC at boot")
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Reviewed-by: Paul Burton <paul.burton@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Patchwork: https://patchwork.linux-mips.org/patch/10739/
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
arch/mips/mti-malta/malta-time.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/arch/mips/mti-malta/malta-time.c b/arch/mips/mti-malta/malta-time.c
index ce02dbd..644ecce 100644
--- a/arch/mips/mti-malta/malta-time.c
+++ b/arch/mips/mti-malta/malta-time.c
@@ -147,14 +147,17 @@ unsigned int get_c0_compare_int(void)
static void __init init_rtc(void)
{
- /* stop the clock whilst setting it up */
- CMOS_WRITE(RTC_SET | RTC_24H, RTC_CONTROL);
+ unsigned char freq, ctrl;
- /* 32KHz time base */
- CMOS_WRITE(RTC_REF_CLCK_32KHZ, RTC_FREQ_SELECT);
+ /* Set 32KHz time base if not already set */
+ freq = CMOS_READ(RTC_FREQ_SELECT);
+ if ((freq & RTC_DIV_CTL) != RTC_REF_CLCK_32KHZ)
+ CMOS_WRITE(RTC_REF_CLCK_32KHZ, RTC_FREQ_SELECT);
- /* start the clock */
- CMOS_WRITE(RTC_24H, RTC_CONTROL);
+ /* Ensure SET bit is clear so RTC can run */
+ ctrl = CMOS_READ(RTC_CONTROL);
+ if (ctrl & RTC_SET)
+ CMOS_WRITE(ctrl & ~RTC_SET, RTC_CONTROL);
}
void __init plat_time_init(void)
--
1.9.1
