Message-ID: <20140903120603.6b73e2a7@bbrezillon>
Date:	Wed, 3 Sep 2014 12:06:03 +0200
From:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
To:	Gaël PORTAY <g.portay@...rkiz.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-pwm@...r.kernel.org, Nicolas Ferre <nicolas.ferre@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Gaël PORTAY <gael.portay@...il.com>
Subject: Re: [PATCHv2 3/4] ARM: at91/tclib: mask interruptions at shutdown
 and probe

Hi Gael,

On Fri, 29 Aug 2014 18:16:42 +0200
Gaël PORTAY <g.portay@...rkiz.com> wrote:

> Shutdown properly the timer counter block by masking interruptions. Otherwise,
> a segmentation may happen when kexec-ing a new kernel (see backtrace below).
> An interruption may happen before the handler is set, leading to a kernel
> segmentation fault.
> 
> Furthermore, we make sure the interruptions are masked when the driver is
> initialized. This will prevent freshly kexec-ed kernel from crashing when
> launched from a kernel which does not properly mask interruptions at shutdown.
> 
> The backtrace below happened after kexec-ing a new kernel, from a kernel
> that did not shut down properly leaving interruptions unmasked.
> 
> Unable to handle kernel NULL pointer dereference at virtual address 00000000
> pgd = c0004000
> [00000000] *pgd=00000000
> Internal error: Oops: 80000005 [#1] ARM
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper Not tainted 3.16.0+ #144
> task: c1828aa0 ti: c182a000 task.ti: c182a000
> PC is at 0x0
> LR is at ch2_irq+0x28/0x30
> pc : [<00000000>]    lr : [<c01db904>]    psr: 000000d3
> sp : c182bd38  ip : c182bd48  fp : c182bd44
> r10: c0373390  r9 : c1825b00  r8 : 60000053
> r7 : 00000000  r6 : 00000000  r5 : 00000013  r4 : c036e800
> r3 : 00000000  r2 : 00002004  r1 : c036e760  r0 : c036e760
> Flags: nzcv  IRQs off  FIQs off  Mode SVC_32  ISA ARM  Segment kernel
> Control: 0005317f  Table: 20004000  DAC: 00000017
> Process swapper (pid: 1, stack limit = 0xc182a1c0)
> Stack: (0xc182bd38 to 0xc182c000)
> bd20:                                                       c182bd7c c182bd48
> bd40: c0045430 c01db8ec 00000000 c18c6f40 c182bd74 c1825b00 c035cec4 00000000
> bd60: c182be2c 60000053 c1825b34 00000000 c182bd94 c182bd80 c0045570 c0045408
> bd80: 00000000 c1825b00 c182bdac c182bd98 c0047f34 c0045550 00000013 c036619c
> bda0: c182bdc4 c182bdb0 c0044da4 c0047e98 0000007f 00000013 c182bde4 c182bdc8
> bdc0: c0009e34 c0044d8c fefff000 c0046728 60000053 ffffffff c182bdf4 c182bde8
> bde0: c00086a8 c0009ddc c182be74 c182bdf8 c000cb80 c0008674 00000000 00000013
> be00: 00000000 00014200 c1825b00 c036e800 00000013 c035ed98 60000053 c1825b34
> be20: 00000000 c182be74 c182be20 c182be40 c0047994 c0046728 60000053 ffffffff
> be40: 00000013 c036e800 c182be64 c1825b00 00000013 c036e800 c035ed98 c03874bc
> be60: 00000004 c036e700 c182be94 c182be78 c004689c c0046398 c036e760 c18c6080
> be80: 00000000 c035ed10 c182bedc c182be98 c0348b08 c004684c 0000000c c034dac8
> bea0: 004c4b3f c028c338 c036e760 00000013 c014ecc8 c18e67e0 c035b9c0 c0348884
> bec0: c035b9c0 c182a020 00000000 00000000 c182bf54 c182bee0 c00089fc c0348894
> bee0: c00da51c c1ffcc78 c182bf0c c182bef8 c002d100 c002d09c c1ffcc78 00000000
> bf00: c182bf54 c182bf10 c002d308 c0336570 c182bf3c c0334e44 00000003 00000003
> bf20: 00000030 c0334b44 c0044d74 00000003 00000003 c034dac8 c0350a94 c0373440
> bf40: c0373440 00000030 c182bf94 c182bf58 c0336d24 c000890c 00000003 00000003
> bf60: c0336560 c182bf64 c182bf64 6e616e0d 00000000 c0272fc8 00000000 00000000
> bf80: 00000000 00000000 c182bfac c182bf98 c0272fd8 c0336bd8 c182a000 00000000
> bfa0: 00000000 c182bfb0 c00095d0 c0272fd8 00000000 00000000 00000000 00000000
> bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
> bfe0: 00000000 00000000 00000000 00000000 00000013 00000000 374d27cd 33cc33e4
> Backtrace:
> [<c01db8dc>] (ch2_irq) from [<c0045430>] (handle_irq_event_percpu+0x38/0x148)
> [<c00453f8>] (handle_irq_event_percpu) from [<c0045570>] (handle_irq_event+0x30/0x40)
>  r10:00000000 r9:c1825b34 r8:60000053 r7:c182be2c r6:00000000 r5:c035cec4
>  r4:c1825b00
> [<c0045540>] (handle_irq_event) from [<c0047f34>] (handle_fasteoi_irq+0xac/0x11c)
>  r4:c1825b00 r3:00000000
> [<c0047e88>] (handle_fasteoi_irq) from [<c0044da4>] (generic_handle_irq+0x28/0x38)
>  r5:c036619c r4:00000013
> [<c0044d7c>] (generic_handle_irq) from [<c0009e34>] (handle_IRQ+0x68/0x88)
>  r4:00000013 r3:0000007f
> [<c0009dcc>] (handle_IRQ) from [<c00086a8>] (at91_aic_handle_irq+0x44/0x4c)
>  r6:ffffffff r5:60000053 r4:c0046728 r3:fefff000
> [<c0008664>] (at91_aic_handle_irq) from [<c000cb80>] (__irq_svc+0x40/0x4c)
> Exception stack(0xc182bdf8 to 0xc182be40)
> bde0:                                                       00000000 00000013
> be00: 00000000 00014200 c1825b00 c036e800 00000013 c035ed98 60000053 c1825b34
> be20: 00000000 c182be74 c182be20 c182be40 c0047994 c0046728 60000053 ffffffff
> [<c0046388>] (__setup_irq) from [<c004689c>] (setup_irq+0x60/0x8c)
>  r10:c036e700 r9:00000004 r8:c03874bc r7:c035ed98 r6:c036e800 r5:00000013
>  r4:c1825b00
> [<c004683c>] (setup_irq) from [<c0348b08>] (tcb_clksrc_init+0x284/0x31c)
>  r6:c035ed10 r5:00000000 r4:c18c6080 r3:c036e760
> [<c0348884>] (tcb_clksrc_init) from [<c00089fc>] (do_one_initcall+0x100/0x1b4)
>  r10:00000000 r9:00000000 r8:c182a020 r7:c035b9c0 r6:c0348884 r5:c035b9c0
>  r4:c18e67e0
> [<c00088fc>] (do_one_initcall) from [<c0336d24>] (kernel_init_freeable+0x15c/0x224)
>  r9:00000030 r8:c0373440 r7:c0373440 r6:c0350a94 r5:c034dac8 r4:00000003
> [<c0336bc8>] (kernel_init_freeable) from [<c0272fd8>] (kernel_init+0x10/0xec)
>  r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:c0272fc8 r4:00000000
> [<c0272fc8>] (kernel_init) from [<c00095d0>] (ret_from_fork+0x14/0x24)
>  r4:00000000 r3:c182a000
> Code: bad PC value
> ---[ end trace 5b30f0017e282e47 ]---
> Kernel panic - not syncing: Fatal exception in interrupt
> 
> Signed-off-by: Gaël PORTAY <gael.portay@...il.com>

Except for the nitpick you'll find below, you have my

Acked-by: Boris Brezillon <boris.brezillon@...e-electrons.com>

> ---
>  drivers/misc/atmel_tclib.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/misc/atmel_tclib.c b/drivers/misc/atmel_tclib.c
> index d505d1e..2f0d84c 100644
> --- a/drivers/misc/atmel_tclib.c
> +++ b/drivers/misc/atmel_tclib.c
> @@ -109,6 +109,7 @@ static int __init tc_probe(struct platform_device *pdev)
>  	struct clk	*clk;
>  	int		irq;
>  	struct resource	*r;
> +	unsigned int	i;
>  
>  	irq = platform_get_irq(pdev, 0);
>  	if (irq < 0)
> @@ -157,18 +158,33 @@ static int __init tc_probe(struct platform_device *pdev)
>  	if (tc->irq[2] < 0)
>  		tc->irq[2] = irq;
>  
> +	for (i = 0; i < 3; i++)
> +		writel(0xff, tc->regs + ATMEL_TC_REG(i, IDR));
> +

How about using the IRQ flags defined in atmel_tc.h instead of the
magic 0xff value ?

		writel(ATMEL_TC_COVFS | ...,
		       tc->regs + ATMEL_TC_REG(i, IDR));

>  	spin_lock(&tc_list_lock);
>  	list_add_tail(&tc->node, &tc_list);
>  	spin_unlock(&tc_list_lock);
>  
> +	platform_set_drvdata(pdev, tc);
> +
>  	return 0;
>  }
>  
> +static void tc_shutdown (struct platform_device *pdev)
> +{
> +	int i;
> +	struct atmel_tc *tc = platform_get_drvdata(pdev);
> +
> +	for (i = 0; i < 3; i++)
> +		writel(0xff, tc->regs + ATMEL_TC_REG(i, IDR));

Ditto

Best Regards,

Boris

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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