Subject: Re: [PATCH v3 6/7] ARM: dts: at91: at91sam9x5: switch to new clock bindings

From: Alexandre Belloni <[email-masked]>
Date: Tue, 20 Aug 2019 21:40:39 +0200

Hi,

On 28/07/2019 22:56:15+0200, Uwe Kleine-König wrote:
> Hello,
> 
> [added tglx to Cc because Alexandre said in irc: 4 or 5 years ago, there
> was some discussion (with tglx) to make the driver not sleep when early
> in the boot process I'll try to dig that up]
> 

This is the discussion I was referring to:
https://lore.kernel.org/lkml/6120818.MyeJZ74hYa@wuerfel/

Incidentally, I think this is the patch you need to fix your issue but I
doesn't apply because the code moved to sckc.c

Afzal then points to tglx's mail:
https://lore.kernel.org/linux-arm-kernel/alpine.DEB.2.11.1606061448010.28031@nanos/

The whole series took 3 years to get in and this patch slipped through
the cracks. I'll resend it to restart the discussion.

However, could you dump the clock tree before and after the switch to
the new clock binding because it should actually change the behaviour
(it should have crashed before the change)  and I fear something else
is selected the wrong slow clock parent.

> On Sat, Jul 27, 2019 at 05:39:43PM +0200, Uwe Kleine-König wrote:
> > Hello Alexandre,
> > 
> > On Mon, Nov 12, 2018 at 02:31:07PM +0100, Alexandre Belloni wrote:
> > > Switch at91sam9x5 boards to the new PMC clock bindings.
> > 
> > This patch results in a broken dtb for my AriettaG25[1]. It compiles
> > fine, but booting results in:
> > 
> > 	SD/MMC: dt blob: Read file acme-arietta.dtb to 0x21000000
> > 	SD: Card Capacity: Standard
> > 	SD: Specification Version 3.0X
> > 
> > 	Booting zImage ......
> > 	zImage magic: 0x16f2818 is found
> > 
> > 	Using device tree in place at 0x21000000
> > 
> > 	Starting linux kernel ..., machid: 0xffffffff
> > 
> > 	Uncompressing Linux... done, booting the kernel.
> > 	Booting Linux on physical CPU 0x0
> > 	Linux version 5.3.0-rc1+ (uwe@taurus) (gcc version 7.3.1 20180201 (OSELAS.Toolchain-2018.02.0 7-20180201)) #4 Sat Jul 27 15:47:15 CEST 2019
> > 	CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=0005317f
> > 	CPU: VIVT data cache, VIVT instruction cache
> > 	OF: fdt: Machine model: Acme Systems Arietta G25
> > 	printk: bootconsole [earlycon0] enabled
> > 	printk: debug: ignoring loglevel setting.
> > 	Memory policy: Data cache writeback
> > 	On node 0 totalpages: 32768
> > 	  Normal zone: 256 pages used for memmap
> > 	  Normal zone: 0 pages reserved
> > 	  Normal zone: 32768 pages, LIFO batch:7
> > 	pcpu-alloc: s0 r0 d32768 u32768 alloc=1*32768
> > 	pcpu-alloc: [0] 0 
> > 	Built 1 zonelists, mobility grouping on.  Total pages: 32512
> > 	Kernel command line: earlyprintk ignore_loglevel  mem=128M console=ttyS0,115200 root=/dev/mmcblk0p2 rootfstype=ext4 rw rootwait
> > 	Dentry cache hash table entries: 16384 (order: 4, 65536 bytes, linear)
> > 	Inode-cache hash table entries: 8192 (order: 3, 32768 bytes, linear)
> > 	mem auto-init: stack:off, heap alloc:off, heap free:off
> > 	Memory: 121352K/131072K available (5826K kernel code, 199K rwdata, 1892K rodata, 232K init, 125K bss, 9720K reserved, 0K cma-reserved)
> > 	NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16
> > 	random: get_random_bytes called from start_kernel+0x294/0x474 with crng_init=0
> > 	bad: scheduling from the idle thread!
> > 	CPU: 0 PID: 0 Comm: swapper Not tainted 5.3.0-rc1+ #4
> > 	Hardware name: Atmel AT91SAM9
> > 	[<c000fc4c>] (unwind_backtrace) from [<c000d654>] (show_stack+0x10/0x18)
> > 	[<c000d654>] (show_stack) from [<c059db74>] (dump_stack+0x18/0x24)
> > 	[<c059db74>] (dump_stack) from [<c00386e8>] (dequeue_task_idle+0x1c/0x34)
> > 	[<c00386e8>] (dequeue_task_idle) from [<c05b5818>] (__schedule+0x250/0x38c)
> > 	[<c05b5818>] (__schedule) from [<c05b59e8>] (schedule+0x94/0xc8)
> > 	[<c05b59e8>] (schedule) from [<c05b876c>] (schedule_hrtimeout_range_clock+0xf4/0x13c)
> > 	[<c05b876c>] (schedule_hrtimeout_range_clock) from [<c05b87cc>] (schedule_hrtimeout_range+0x18/0x24)
> > 	[<c05b87cc>] (schedule_hrtimeout_range) from [<c05b8240>] (usleep_range+0x70/0x98)
> > 	[<c05b8240>] (usleep_range) from [<c02a18a0>] (clk_slow_rc_osc_prepare+0x28/0x34)
> > 	[<c02a18a0>] (clk_slow_rc_osc_prepare) from [<c029af78>] (clk_core_prepare+0x84/0xa0)
> > 	[<c029af78>] (clk_core_prepare) from [<c029af54>] (clk_core_prepare+0x60/0xa0)
> > 	[<c029af54>] (clk_core_prepare) from [<c029b790>] (clk_prepare+0x1c/0x30)
> > 	[<c029b790>] (clk_prepare) from [<c02f1310>] (regmap_mmio_attach_clk+0x1c/0x24)
> > 	[<c02f1310>] (regmap_mmio_attach_clk) from [<c02f7a98>] (of_syscon_register+0x218/0x268)
> > 	[<c02f7a98>] (of_syscon_register) from [<c02f7b18>] (syscon_node_to_regmap+0x30/0x58)
> > 	[<c02f7b18>] (syscon_node_to_regmap) from [<c07d2f7c>] (at91sam9x5_pmc_setup+0x78/0x430)
> > 	[<c07d2f7c>] (at91sam9x5_pmc_setup) from [<c07cfe88>] (of_clk_init+0x188/0x21c)
> > 	[<c07cfe88>] (of_clk_init) from [<c07c062c>] (time_init+0x1c/0x2c)
> > 	[<c07c062c>] (time_init) from [<c07bcbec>] (start_kernel+0x2c4/0x474)
> > 	[<c07bcbec>] (start_kernel) from [<00000000>] (0x0)
> > 	bad: scheduling from the idle thread!
> > 	CPU: 0 PID: 0 Comm: swapper Not tainted 5.3.0-rc1+ #4
> > 	Hardware name: Atmel AT91SAM9
> > 	[<c000fc4c>] (unwind_backtrace) from [<c000d654>] (show_stack+0x10/0x18)
> > 	[<c000d654>] (show_stack) from [<c059db74>] (dump_stack+0x18/0x24)
> > 	[<c059db74>] (dump_stack) from [<c00386e8>] (dequeue_task_idle+0x1c/0x34)
> > 	[<c00386e8>] (dequeue_task_idle) from [<c05b5818>] (__schedule+0x250/0x38c)
> > 	[<c05b5818>] (__schedule) from [<c05b59e8>] (schedule+0x94/0xc8)
> > 	[<c05b59e8>] (schedule) from [<c05b876c>] (schedule_hrtimeout_range_clock+0xf4/0x13c)
> > 	[<c05b876c>] (schedule_hrtimeout_range_clock) from [<c05b87cc>] (schedule_hrtimeout_range+0x18/0x24)
> > 	[<c05b87cc>] (schedule_hrtimeout_range) from [<c05b8240>] (usleep_range+0x70/0x98)
> > 	[<c05b8240>] (usleep_range) from [<c02a18a0>] (clk_slow_rc_osc_prepare+0x28/0x34)
> > 	[<c02a18a0>] (clk_slow_rc_osc_prepare) from [<c029af78>] (clk_core_prepare+0x84/0xa0)
> > 	[<c029af78>] (clk_core_prepare) from [<c029af54>] (clk_core_prepare+0x60/0xa0)
> > 	[<c029af54>] (clk_core_prepare) from [<c029b790>] (clk_prepare+0x1c/0x30)
> > 	[<c029b790>] (clk_prepare) from [<c02f1310>] (regmap_mmio_attach_clk+0x1c/0x24)
> > 	[<c02f1310>] (regmap_mmio_attach_clk) from [<c02f7a98>] (of_syscon_register+0x218/0x268)
> > 	[<c02f7a98>] (of_syscon_register) from [<c02f7b18>] (syscon_node_to_regmap+0x30/0x58)
> > 	[<c02f7b18>] (syscon_node_to_regmap) from [<c07d2f7c>] (at91sam9x5_pmc_setup+0x78/0x430)
> > 	[<c07d2f7c>] (at91sam9x5_pmc_setup) from [<c07cfe88>] (of_clk_init+0x188/0x21c)
> > 	[<c07cfe88>] (of_clk_init) from [<c07c062c>] (time_init+0x1c/0x2c)
> > 	[<c07c062c>] (time_init) from [<c07bcbec>] (start_kernel+0x2c4/0x474)
> > 	[<c07bcbec>] (start_kernel) from [<00000000>] (0x0)
> > 	bad: scheduling from the idle thread!
> > 	CPU: 0 PID: 0 Comm: swapper Not tainted 5.3.0-rc1+ #4
> > 	Hardware name: Atmel AT91SAM9
> > 	...
> > 
> > The error message repeats without end. (I obviously didn't test until
> > the end :-), but after 10 minutes the machine still prints this message.)
> > 
> > With the old dtb Linux 5.3-rc1 boots just fine. I assume this is not
> > related to my dts or .config so I'm not attaching these here. If you're
> > interested I can provide them of course.
> 
> With the following diff applied, the machine boots just fine:
> 
> diff --git a/drivers/clk/at91/sckc.c b/drivers/clk/at91/sckc.c
> index 9bfe9a28294a..4d2be45be916 100644
> --- a/drivers/clk/at91/sckc.c
> +++ b/drivers/clk/at91/sckc.c
> @@ -187,7 +187,7 @@ static int clk_slow_rc_osc_prepare(struct clk_hw *hw)
>  
>  	writel(readl(sckcr) | osc->bits->cr_rcen, sckcr);
>  
> -	usleep_range(osc->startup_usec, osc->startup_usec + 1);
> +	udelay(osc->startup_usec);
>  
>  	return 0;
>  }
> 
> Best regards
> Uwe

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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