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[PATCH 3.14 02/44] MIPS: Malta: Dont reinitialise RTC

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3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: James Hogan <james.hogan@imgtec.com>

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@imgtec.com>
Reviewed-by: Paul Burton <paul.burton@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10739/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/mti-malta/malta-time.c |   15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

--- a/arch/mips/mti-malta/malta-time.c
+++ b/arch/mips/mti-malta/malta-time.c
@@ -168,14 +168,17 @@ 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)


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[PATCH 3.14 00/44] 3.14.51-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:00 +0200
  [PATCH 3.14 40/44] dcache: dont need rcu in shrink_dentry_list() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:00 +0200
  [PATCH 3.14 44/44] mm, vmscan: Do not wait for page writeback for GFP_NOFS allocations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:00 +0200
  [PATCH 3.14 31/44] signal: fix information leak in copy_siginfo_to_user Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:00 +0200
  [PATCH 3.14 03/44] MIPS: Fix sched_getaffinity with MT FPAFF enabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:00 +0200
  [PATCH 3.14 42/44] path_openat(): fix double fput() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:00 +0200
  [PATCH 3.14 38/44] dont remove from shrink list in select_collect() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:00 +0200
  [PATCH 3.14 30/44] signalfd: fix information leak in signalfd_copyinfo Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:00 +0200
  [PATCH 3.14 24/44] ALSA: hda - fix cs4210_spdif_automute() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 20/44] crypto: ixp4xx - Remove bogus BUG_ON on scattered dst buffer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 25/44] ipc: modify message queue accounting to not take kernel data structures into account Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 18/44] x86/xen: Probe target addresses in set_aliased_prot() before the hypercall Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 21/44] rbd: fix copyup completion race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 15/44] ARM: sunxi: fix build for THUMB2_KERNEL Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 13/44] ima: extend "mask" policy matching support Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 22/44] ARM: OMAP2+: hwmod: Fix _wait_target_ready() for hwmods without sysc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 27/44] PCI: Restore PCI_MSIX_FLAGS_BIRMASK definition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 05/44] fsnotify: fix oops in fsnotify_clear_marks_by_group_flags() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 34/44] fold try_prune_one_dentry() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 14/44] md: use kzalloc() when bitmap is disabled Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 17/44] ASoC: pcm1681: Fix setting de-emphasis sampling rate selection Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 23/44] iscsi-target: Fix iscsit_start_kthreads failure OOPs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 06/44] drm/radeon/combios: add some validation of lvds values Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 16/44] [PATCH] sparc64: Fix userspace FPU register corruptions. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 11/44] USB: sierra: add 1199:68AB device ID Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 26/44] ocfs2: fix BUG in ocfs2_downconvert_thread_do_work() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 12/44] ima: add support for new "euid" policy condition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 01/44] ARM: realview: fix sparsemem build Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 33/44] fold d_kill() and d_free() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 02/44] MIPS: Malta: Dont reinitialise RTC Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 04/44] MIPS: Make set_pte() SMP safe. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  [PATCH 3.14 32/44] signal: fix information leak in copy_siginfo_from_user32 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2015-08-14 20:10 +0200
  Re: [PATCH 3.14 00/44] 3.14.51-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2015-08-15 02:20 +0200
  Re: [PATCH 3.14 00/44] 3.14.51-stable review Guenter Roeck <linux@roeck-us.net> - 2015-08-15 17:20 +0200

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