[PATCH 029/139] ARM: i.MX25: clk: parent per5_clk to AHB clock

[Luis Henriques]

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

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

From: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx>

commit 4b526ca5f627188425184a22ed46c91baa602d43 upstream.

The mxc-timer on the imx25 needs to be derived from the AHB clock.
If a bootloader reparents this clock to the ipg_clk_highfreq, which according
to the datasheet is a valid operation, the system can/will produce lockups/
freezes after some time [1].

This can be forced with code like
	while(1)
                syscall(SYS_clock_gettime, CLOCK_REALTIME, &tp);

This was already fixed with the commit
	"i.MX25 GPT clock fix: ensure correct the clock source" [2],
for 3.1-rc2, but was lost, when i.MX was converted to the common clock framework
("ARM i.MX25: implement clocks using common clock framework") [3]

[1]: http://lists.arm.linux.org.uk/lurker/message/20130129.161230.229bda17.en.html
[2]: 2012d9ca2a1381ae3e733330a7f0d1d2f1988bba
[3]: 6bbaec5676e4f475b0d78743cbd4c70a8804ce14

Signed-off-by: Steffen Trumtrar <s.trumtrar@xxxxxxxxxxxxxx>
Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
[ luis: adjust context ]
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 arch/arm/mach-imx/clk-imx25.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm/mach-imx/clk-imx25.c b/arch/arm/mach-imx/clk-imx25.c
index 4431a62..ec376d3 100644
--- a/arch/arm/mach-imx/clk-imx25.c
+++ b/arch/arm/mach-imx/clk-imx25.c
@@ -241,6 +241,9 @@ int __init mx25_clocks_init(void)
 	clk_register_clkdev(clk[sdma_ahb], "ahb", "imx35-sdma");
 	clk_register_clkdev(clk[iim_ipg], "iim", NULL);
 
+	/* Clock source for gpt must be derived from AHB */
+	clk_set_parent(clk[per5_sel], clk[ahb]);
+
 	mxc_timer_init(MX25_IO_ADDRESS(MX25_GPT1_BASE_ADDR), 54);
 	return 0;
 }
-- 
1.8.1.2

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