From: Rajendra Nayak <rnayak@ti.com>
Date: Fri, 23 Aug 2013 10:48:42 +0000 (-0600)
Subject: ARM: OMAP4: clock: Lock PLLs in the right sequence
X-Git-Tag: omap-for-v3.12/prcm-signed^2^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=eeb6603fdde253a8e9129712ce24128d732bd4e7;p=pandora-kernel.git

ARM: OMAP4: clock: Lock PLLs in the right sequence

On OMAP4 we have clk_set_rate()s being done for a few
DPLL clock nodes, as part of the clock init code, since
the bootloaders no longer locks these DPLLs.

So we have a clk_set_rate() done for a ABE DPLL node (which
inturn locks it) followed by a clk_set_rate() for the USB DPLL.

With USB DPLL being in bypass, we have this parent->child
relationship thats formed while the clocks get registered.

dpll_abe_ck
    |
    V
dpll_abe_x2_ck
    |
    V
dpll_abe_m3x2_ck
    |
    V
usb_hs_clk_div_ck
    |
    V
dpll_usb_ck

This is because usb_hs_clk_div_ck is bypass clock for dpll_usb_ck.

So with this parent->child relationship in place, a clk_set_rate()
on ABE DPLL results eventually in a clk_set_rate() call on USB DPLL,
because CCF does a clk_change_rate() (as part of clk_set_rate()) on
all downstream clocks resulting from a rate change on the top clock.

So its important that we lock USB DPLL before we lock ABE DPLL.
Without which we see these error logs at boot.
[These error logs will not be seen if using a bootloader that locks
USB DPLL]

[    0.000000] clock: dpll_usb_ck failed transition to 'locked'
[    0.000000] Division by zero in kernel.
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[    0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[    0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[    0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[    0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[    0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[    0.000000] Division by zero in kernel.
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[    0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[    0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[    0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[    0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[    0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[    0.000000] Division by zero in kernel.
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[    0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[    0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[    0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[    0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[    0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[    0.000000] Division by zero in kernel.
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[    0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[    0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[    0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[    0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[    0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[    0.000000] Division by zero in kernel.
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[    0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[    0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[    0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[    0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[    0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[    0.000000] Division by zero in kernel.
[    0.000000] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-03445-gfb2af00-dirty #7
[    0.000000] [<c001bfe8>] (unwind_backtrace+0x0/0xf4) from [<c001868c>] (show_stack+0x10/0x14)
[    0.000000] [<c001868c>] (show_stack+0x10/0x14) from [<c02deb28>] (Ldiv0+0x8/0x10)
[    0.000000] [<c02deb28>] (Ldiv0+0x8/0x10) from [<c0477030>] (clk_divider_set_rate+0x10/0x114)
[    0.000000] [<c0477030>] (clk_divider_set_rate+0x10/0x114) from [<c0476ef4>] (clk_change_rate+0x38/0xb8)
[    0.000000] [<c0476ef4>] (clk_change_rate+0x38/0xb8) from [<c0476f5c>] (clk_change_rate+0xa0/0xb8)
[    0.000000] clock: trace_clk_div_ck: could not find divisor for target rate 0 for parent pmd_trace_clk_mux_ck
[    0.000000] Division by zero in kernel.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
---

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