Hi Jerome,

On 29/06/17 09:50, Jerome Brunet wrote:

On Wed, 2017-06-28 at 18:07 +0100, Sudeep Holla wrote:

quoted

On 28/06/17 17:46, Jerome Brunet wrote:

quoted

On Wed, 2017-06-28 at 16:52 +0100, Sudeep Holla wrote:

[..]

quoted

quoted

Thanks for this stack. I just worked out the same path now. I did come
up with the patch as below. That should work if my understanding is
correct.

I tried.

Thanks.

quoted

It does not work unfortunately. Still crashes but somewhere else:
[    2.301482] [<ffff00000849e67c>] scpi_of_clk_src_get+0x14/0x58
[    2.307261] [<ffff000008495f40>] __of_clk_get_by_name+0x100/0x118
[    2.313297] [<ffff000008495fac>] clk_get+0x2c/0x78
[    2.318044] [<ffff00000856f4d0>] dev_pm_opp_get_opp_table+0xb0/0x118
[    2.324338] [<ffff00000856fd00>] dev_pm_opp_add+0x20/0x68
[    2.329687] [<ffff0000087a04f8>] scpi_init_opp_table+0xa8/0x188
[    2.335550] [<ffff00000879fb20>]
_get_cluster_clk_and_freq_table+0x80/0x180
[    2.342450] [<ffff0000087a0010>] bL_cpufreq_init+0x3f0/0x480
[    2.348056] [<ffff00000879e4a0>] cpufreq_online+0xc0/0x658
[    2.353490] [<ffff00000879eac8>] cpufreq_add_dev+0x78/0x88
[    2.358924] [<ffff00000855b684>] subsys_interface_register+0x84/0xc8
[    2.365220] [<ffff00000879d8f8>] cpufreq_register_driver+0x138/0x1b8
[    2.371516] [<ffff0000087a0114>] bL_cpufreq_register+0x74/0x120
[    2.377381] [<ffff0000087a0600>] scpi_cpufreq_probe+0x28/0x38
[    2.383076] [<ffff00000855efb0>] platform_drv_probe+0x50/0xb8
[    2.388766] [<ffff00000855d144>] driver_probe_device+0x21c/0x2d8

Looks like a different route and I know why. I have added an extra check
now which should work if I have not missed anything more.

quoted

I have not looked at ALL the clock providers, but I have seen a few and I
don't
remember seeing any which fails, at some point, to register a clocks and
still
register successfully. 

No problem, as I said I am fine with the patch you sent as a fix for now
but just curious to know what are the issues to be fixed to continue
supporting that feature. Please bear with me.

I am :) and I understand what you are trying to do, having a degraded clock
provider is better than nothing according to you, correct?

I'm wondering whether this is correct or not, that why I'm challenging this a
bit.

Fair enough. But the situation I had on my platform is that it provides
DVFS support for 2 CPU clusters and 1 GPU domain. I didn't want to block
using CPUFreq until GPU DVFS was properly supported in the firmware.
I had similar situation with the clock and hence I allowed it to continue.

If you failed to register an scpi clock it is probably because the communication
with the FW is not working, or at least 'not that good', right ?

Not exactly, what if the error is for that particular clock. That's my
point. If we have reached so far means the communication is fine. Just a
fault piece of hardware which may not be critical.

If for some reason, you manage to register some other clocks from the same FW,
how confident can you be that communication will be ok for them ? that the
settings you request will be applied correctly ?

Not sure, I am not registering the clock. Think SCPI as a single clock
provider with multiple clock outputs. You don't want to disable it
entirely if one of the clock outputs have problem. That's my counter
argument.

Is it possible that you may be causing more harm/damage playing with a broken HW
?

Not sure how if we are not registering that clock output from the h/w
clock provider perspective.

quoted

quoted

It seems strange to continue with a broken controller.

I would have agreed if it was single driver or h/w controlled by Linux.
Since it's in the firmware, we should allow the working clocks/opps to
work though few are broken. It's not good if we had to disable
everything if some piece of firmware is not yet ready or broken.
But again, we can get it working later, for now, I am fine with you patch.

I tried your last version, and it does not Oops, at least not for me.

The end result still looks odd to me:
[    1.115219] scpi_clocks scpi:clocks: failed to register clock 'vcpu'
[    1.159490] cpu cpu0: _get_cluster_clk_and_freq_table: Failed to get clk for
cpu: 0, cluster: 0
[    1.162986] cpu cpu0: _get_cluster_clk_and_freq_table: Failed to get data for
cluster: 0
[    1.170945] cpu cpu1: _get_cluster_clk_and_freq_table: Failed to get clk for
cpu: 1, cluster: 0
[    1.179634] cpu cpu1: _get_cluster_clk_and_freq_table: Failed to get data for
cluster: 0
[    1.187654] cpu cpu2: _get_cluster_clk_and_freq_table: Failed to get clk for
cpu: 2, cluster: 0
[    1.196284] cpu cpu2: _get_cluster_clk_and_freq_table: Failed to get data for
cluster: 0
[    1.204375] cpu cpu3: _get_cluster_clk_and_freq_table: Failed to get clk for
cpu: 3, cluster: 0
[    1.212911] cpu cpu3: _get_cluster_clk_and_freq_table: Failed to get data for
cluster: 0
[    1.220612] arm_big_little: bL_cpufreq_register: Registered platform driver:
scpi

So now, I have an scpi clock provider which registers successfully but fails to
register its only clock. As a consequence, I also have a cpufreq driver which
manages to register but has no clock cpu clock to drive ...

Yes, I agree the above is not entirely acceptable situation.

-- 
Regards,
Sudeep