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

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

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]

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