Re: [PATCH v6 1/4] clk: imx: Add CLK_IS_CRITICAL flag for busy divider and busy mux

[Stefan Agner <stefan@agner.ch>]

On 18.04.2018 15:03, Jacky Bai wrote:
>> Subject: Re: [PATCH v6 1/4] clk: imx: Add CLK_IS_CRITICAL flag for busy
>> divider and busy mux
>>
>> Hi Bai,
>>
>> On 20.03.2018 03:24, Bai Ping wrote:
>> > The busy divider and busy mux is actually used by the system critical
>> > clocks, so add 'CLK_IS_CRITICAL' to clocks registered with these two type.
>>
>> This seems that this patch breaks i.MX 6ULL. Our Colibri iMX6ULL freezes with
>> v4.17-rc1:
>>
> 
> Thanks for you report this. I will try on imx6ull and look into it.
> 

I just sent a possible fix for this, unfortunately I forgot to add you
to the recipients list, sorry about that:
https://patchwork.kernel.org/patch/10348099/

However, I am not 100% sure why this leads to a crash and whether that
fix is good enough. It would be best if somebody with better clocking
overview could have a closer look at that...

--
Stefan

> BR
> Jacky Bai
>> [    0.000000] Booting Linux on physical CPU 0x0
>> [    0.000000] Linux version 4.17.0-rc1-00002-g7529efa14a7c-dirty
>> (ags@trochilidae) (gcc version 7.2.1 20171011 (Linaro GCC 7.2-2017.11))
>> #517 SMP Wed Apr 18 11:11:07 CEST 2018
>> [    0.000000] CPU: ARMv7 Processor [410fc075] revision 5 (ARMv7),
>> cr=10c5387d
>> [    0.000000] CPU: div instructions available: patching division code
>> [    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing
>> instruction cache
>> [    0.000000] OF: fdt: Machine model: Toradex Colibri iMX6ULL 512MB on
>> Colibri Evaluation Board V3
>> [    0.000000] earlycon: ec_imx6q0 at MMIO 0x02020000 (options
>> '115200n8')
>> [    0.000000] bootconsole [ec_imx6q0] enabled
>> [    0.000000] debug: ignoring loglevel setting.
>> [    0.000000] Memory policy: Data cache writealloc
>> [    0.000000] cma: Reserved 256 MiB at 0x90000000
>> [    0.000000] On node 0 totalpages: 131072
>> [    0.000000]   Normal zone: 1024 pages used for memmap
>> [    0.000000]   Normal zone: 0 pages reserved
>> [    0.000000]   Normal zone: 131072 pages, LIFO batch:31
>> [    0.000000] random: fast init done
>> [    0.000000] percpu: Embedded 16 pages/cpu @(ptrval) s35084 r8192
>> d22260 u65536
>> [    0.000000] pcpu-alloc: s35084 r8192 d22260 u65536 alloc=16*4096
>> [    0.000000] pcpu-alloc: [0] 0
>> [    0.000000] Built 1 zonelists, mobility grouping on.  Total pages:
>> 130048
>> [    0.000000] Kernel command line:
>> mtdparts=gpmi-nand:512k(mx6ull-bcb),1536k(u-boot1)ro,1536k(u-
>> boot2)ro,512k(u-boot-env),-(ubi)
>> earlycon user_debug=31 ignore_loglevel ubi.mtd=ubi root=ubi0:rootfs rw
>> rootfstype=ubifs ubi.fm_autoconvert=1 consoleblank=0
>> no_console_suspend=1 console=tty1 console=ttymxc0,115200n8
>> [    0.000000] Dentry cache hash table entries: 65536 (order: 6, 262144
>> bytes)
>> [    0.000000] Inode-cache hash table entries: 32768 (order: 5, 131072
>> bytes)
>> [    0.000000] Memory: 243904K/524288K available (8192K kernel code,
>> 365K rwdata, 2720K rodata, 1024K init, 389K bss, 18240K reserved, 262144K
>> cma-reserved)
>> [    0.000000] Virtual kernel memory layout:
>> [    0.000000]     vector  : 0xffff0000 - 0xffff1000   (   4 kB)
>> [    0.000000]     fixmap  : 0xffc00000 - 0xfff00000   (3072 kB)
>> [    0.000000]     vmalloc : 0xe0800000 - 0xff800000   ( 496 MB)
>> [    0.000000]     lowmem  : 0xc0000000 - 0xe0000000   ( 512 MB)
>> [    0.000000]     modules : 0xbf000000 - 0xc0000000   (  16 MB)
>> [    0.000000]       .text : 0x(ptrval) - 0x(ptrval)   (9184 kB)
>> [    0.000000]       .init : 0x(ptrval) - 0x(ptrval)   (1024 kB)
>> [    0.000000]       .data : 0x(ptrval) - 0x(ptrval)   ( 366 kB)
>> [    0.000000]        .bss : 0x(ptrval) - 0x(ptrval)   ( 390 kB)
>> [    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1,
>> Nodes=1
>> [    0.000000] Hierarchical RCU implementation.
>> [    0.000000]  RCU restricting CPUs from NR_CPUS=4 to nr_cpu_ids=1.
>> [    0.000000] RCU: Adjusting geometry for rcu_fanout_leaf=16,
>> nr_cpu_ids=1
>> [    0.000000] NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16
>> <freeze>
>>
>> Yet need to understand what is exactly going on.
>>
>> --
>> Stefan
>>
>>
>> >
>> > Signed-off-by: Bai Ping <ping.bai@nxp.com>
>> > Acked-by: Dong Aisheng <aisheng.dong@nxp.com>
>> > ---
>> >  change from V3->v4:
>> >  - fix a typo in commit log
>> >  change from v4->v5:
>> >  - optimize the commit subject
>> >  change from v5->v6:
>> >  - no change
>> > ---
>> >  drivers/clk/imx/clk-busy.c | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/clk/imx/clk-busy.c b/drivers/clk/imx/clk-busy.c
>> > index 6df3389..9903652 100644
>> > --- a/drivers/clk/imx/clk-busy.c
>> > +++ b/drivers/clk/imx/clk-busy.c
>> > @@ -101,7 +101,7 @@ struct clk *imx_clk_busy_divider(const char *name,
>> > const char *parent_name,
>> >
>> >  	init.name = name;
>> >  	init.ops = &clk_busy_divider_ops;
>> > -	init.flags = CLK_SET_RATE_PARENT;
>> > +	init.flags = CLK_SET_RATE_PARENT | CLK_IS_CRITICAL;
>> >  	init.parent_names = &parent_name;
>> >  	init.num_parents = 1;
>> >
>> > @@ -175,7 +175,7 @@ struct clk *imx_clk_busy_mux(const char *name,
>> > void __iomem *reg, u8 shift,
>> >
>> >  	init.name = name;
>> >  	init.ops = &clk_busy_mux_ops;
>> > -	init.flags = 0;
>> > +	init.flags = CLK_IS_CRITICAL;
>> >  	init.parent_names = parent_names;
>> >  	init.num_parents = num_parents;