clk: exynos: use irqsave version of spin_lock to avoid deadlock with irqs

It is allowed to enable/disable clocks from interrupts, so common Exynos
ARM clock management code for CPUfreq should use 'irqsave' version of
spin_lock calls to avoid potential deadlock caused by spin_lock recursion.
The same spin_lock is used by gate/mux clocks during enable/disable calls.

This deadlock, can be reproduced by enabling CPUfreq (ondemand or
userspace) and decoding video with s5p-mfc driver.

Relevant stack trace:
[ 5928.061534] BUG: spinlock recursion on CPU#0, bash/1252
[ 5928.061609]  lock: 0xee80454c, .magic: dead4ead, .owner: bash/1252, .owner_cpu: 0
[ 5928.068586] CPU: 0 PID: 1252 Comm: bash Tainted: G        W       4.4.0-rc4-00001-g447a7fd #678
[ 5928.077260] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
[ 5928.083359] [<c00153dc>] (unwind_backtrace) from [<c00121b4>] (show_stack+0x10/0x14)
[ 5928.091072] [<c00121b4>] (show_stack) from [<c0213e28>] (dump_stack+0x68/0xb8)
[ 5928.098275] [<c0213e28>] (dump_stack) from [<c005c1ec>] (do_raw_spin_lock+0x184/0x1ac)
[ 5928.106177] [<c005c1ec>] (do_raw_spin_lock) from [<c05cfa98>] (_raw_spin_lock_irqsave+0x20/0x28)
[ 5928.114943] [<c05cfa98>] (_raw_spin_lock_irqsave) from [<c0468698>] (clk_gate_endisable+0x24/0x98)
[ 5928.123882] [<c0468698>] (clk_gate_endisable) from [<c0464d40>] (clk_core_disable+0x60/0x84)
[ 5928.132299] [<c0464d40>] (clk_core_disable) from [<c0465e00>] (clk_disable+0x24/0x30)
[ 5928.140117] [<c0465e00>] (clk_disable) from [<c03f3b80>] (s5p_mfc_handle_frame+0x254/0x860)
[ 5928.148445] [<c03f3b80>] (s5p_mfc_handle_frame) from [<c03f4b34>] (s5p_mfc_irq+0x890/0xa24)
[ 5928.156778] [<c03f4b34>] (s5p_mfc_irq) from [<c00627bc>] (handle_irq_event_percpu+0x50/0x14c)
[ 5928.165283] [<c00627bc>] (handle_irq_event_percpu) from [<c00628f0>] (handle_irq_event+0x38/0x5c)
[ 5928.174143] [<c00628f0>] (handle_irq_event) from [<c0065864>] (handle_fasteoi_irq+0xdc/0x1a4)
[ 5928.182645] [<c0065864>] (handle_fasteoi_irq) from [<c0062090>] (generic_handle_irq+0x18/0x28)
[ 5928.191236] [<c0062090>] (generic_handle_irq) from [<c00621a4>] (__handle_domain_irq+0x6c/0xdc)
[ 5928.199917] [<c00621a4>] (__handle_domain_irq) from [<c0009470>] (gic_handle_irq+0x4c/0x98)
[ 5928.208249] [<c0009470>] (gic_handle_irq) from [<c0012c54>] (__irq_svc+0x54/0x90)
[ 5928.215709] Exception stack(0xeddb5cb8 to 0xeddb5d00)
[ 5928.220745] 5ca0:                                                       ee80454c faddfadc
[ 5928.228906] 5cc0: 00000000 01000001 ee831ce0 f8114200 ee807c00 01130520 00000403 eddb5d84
[ 5928.237063] 5ce0: ee807c48 2faf0800 ee807c0c eddb5d08 c046b618 c046b634 20000053 ffffffff
[ 5928.245225] [<c0012c54>] (__irq_svc) from [<c046b634>] (exynos_cpuclk_notifier_cb+0x170/0x270)
[ 5928.253823] [<c046b634>] (exynos_cpuclk_notifier_cb) from [<c003cb58>] (notifier_call_chain+0x44/0x84)
[ 5928.263106] [<c003cb58>] (notifier_call_chain) from [<c003ccd4>] (__srcu_notifier_call_chain+0x6c/0x9c)
[ 5928.272480] [<c003ccd4>] (__srcu_notifier_call_chain) from [<c003cd1c>] (srcu_notifier_call_chain+0x18/0x20)
[ 5928.282288] [<c003cd1c>] (srcu_notifier_call_chain) from [<c0464ed0>] (__clk_notify+0x6c/0x74)
[ 5928.290881] [<c0464ed0>] (__clk_notify) from [<c0465388>] (clk_propagate_rate_change+0xa0/0xac)
[ 5928.299561] [<c0465388>] (clk_propagate_rate_change) from [<c0465378>] (clk_propagate_rate_change+0x90/0xac)
[ 5928.309370] [<c0465378>] (clk_propagate_rate_change) from [<c04666fc>] (clk_core_set_rate_nolock+0x64/0xa8)
[ 5928.319091] [<c04666fc>] (clk_core_set_rate_nolock) from [<c0466760>] (clk_set_rate+0x20/0x30)
[ 5928.327686] [<c0466760>] (clk_set_rate) from [<c0428c70>] (set_target+0xe8/0x23c)
[ 5928.335152] [<c0428c70>] (set_target) from [<c04244d0>] (__cpufreq_driver_target+0x184/0x29c)
[ 5928.343655] [<c04244d0>] (__cpufreq_driver_target) from [<c0427128>] (cpufreq_set+0x44/0x64)
[ 5928.352074] [<c0427128>] (cpufreq_set) from [<c0423948>] (store_scaling_setspeed+0x5c/0x74)
[ 5928.360407] [<c0423948>] (store_scaling_setspeed) from [<c04238d0>] (store+0x7c/0x98)
[ 5928.368221] [<c04238d0>] (store) from [<c0132540>] (sysfs_kf_write+0x44/0x48)
[ 5928.375338] [<c0132540>] (sysfs_kf_write) from [<c0131b9c>] (kernfs_fop_write+0xb8/0x1bc)
[ 5928.383496] [<c0131b9c>] (kernfs_fop_write) from [<c00d71f8>] (__vfs_write+0x2c/0xd4)
[ 5928.391308] [<c00d71f8>] (__vfs_write) from [<c00d7de8>] (vfs_write+0xa0/0x144)
[ 5928.398598] [<c00d7de8>] (vfs_write) from [<c00d8048>] (SyS_write+0x44/0x84)
[ 5928.405631] [<c00d8048>] (SyS_write) from [<c000f540>] (ret_fast_syscall+0x0/0x3c)

CC: stable@vger.kernel.org  # v4.2+
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>

drivers/clk/samsung/clk-cpu.c

@@ -148,6 +148,7 @@ static int exynos_cpuclk_pre_rate_change(struct clk_notifier_data *ndata,
 	unsigned long alt_prate = clk_get_rate(cpuclk->alt_parent);
 	unsigned long alt_div = 0, alt_div_mask = DIV_MASK;
 	unsigned long div0, div1 = 0, mux_reg;
+	unsigned long flags;
 
 	/* find out the divider values to use for clock data */
 	while ((cfg_data->prate * 1000) != ndata->new_rate) {
@@ -156,7 +157,7 @@ static int exynos_cpuclk_pre_rate_change(struct clk_notifier_data *ndata,
 		cfg_data++;
 	}
 
-	spin_lock(cpuclk->lock);
+	spin_lock_irqsave(cpuclk->lock, flags);
 
 	/*
 	 * For the selected PLL clock frequency, get the pre-defined divider
@@ -212,7 +213,7 @@ static int exynos_cpuclk_pre_rate_change(struct clk_notifier_data *ndata,
 				DIV_MASK_ALL);
 	}
 
-	spin_unlock(cpuclk->lock);
+	spin_unlock_irqrestore(cpuclk->lock, flags);
 	return 0;
 }
 
@@ -223,6 +224,7 @@ static int exynos_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
 	const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
 	unsigned long div = 0, div_mask = DIV_MASK;
 	unsigned long mux_reg;
+	unsigned long flags;
 
 	/* find out the divider values to use for clock data */
 	if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
@@ -233,7 +235,7 @@ static int exynos_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
 		}
 	}
 
-	spin_lock(cpuclk->lock);
+	spin_lock_irqsave(cpuclk->lock, flags);
 
 	/* select mout_apll as the alternate parent */
 	mux_reg = readl(base + E4210_SRC_CPU);
@@ -246,7 +248,7 @@ static int exynos_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
 	}
 
 	exynos_set_safe_div(base, div, div_mask);
-	spin_unlock(cpuclk->lock);
+	spin_unlock_irqrestore(cpuclk->lock, flags);
 	return 0;
 }