Re: [PATCH] clk: scpi: error when clock fails to register

[Jerome Brunet <jbrunet@baylibre.com>]

On Wed, 2017-06-28 at 18:07 +0100, Sudeep Holla wrote:
> 
> On 28/06/17 17:46, Jerome Brunet wrote:
> > On Wed, 2017-06-28 at 16:52 +0100, Sudeep Holla wrote:
> 
> [..]
> 
> > > 
> > > 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.
> 
> > 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.
> 
> > 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.

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 ?

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 ?

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

> 
> > 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 ...

> 
> Regards,
> Sudeep
> 
> ---
> 
> diff --git i/drivers/clk/clk-scpi.c w/drivers/clk/clk-scpi.c
> index 96d37175d0ad..a0b9b4c84be3 100644
> --- i/drivers/clk/clk-scpi.c
> +++ w/drivers/clk/clk-scpi.c
> @@ -192,7 +192,7 @@ scpi_of_clk_src_get(struct of_phandle_args *clkspec,
> void *data)
> 
>         for (count = 0; count < clk_data->clk_num; count++) {
>                 sclk = clk_data->clk[count];
> -               if (idx == sclk->id)
> +               if (sclk && idx == sclk->id)
>                         return &sclk->hw;
>         }
> 
> @@ -245,11 +245,14 @@ static int scpi_clk_add(struct device *dev, struct
> device_node *np,
>                 sclk->id = val;
> 
>                 err = scpi_clk_ops_init(dev, match, sclk, name);
> -               if (err)
> +               if (err) {
>                         dev_err(dev, "failed to register clock '%s'\n",
> name);
> -               else
> +                       clk_data->clk[idx] = NULL;
> +                       devm_kfree(dev, sclk);
> +               } else {
>                         dev_dbg(dev, "Registered clock '%s'\n", name);
> -               clk_data->clk[idx] = sclk;
> +                       clk_data->clk[idx] = sclk;
> +               }
>         }
> 
>         return of_clk_add_hw_provider(np, scpi_of_clk_src_get, clk_data);
> 
> --
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