Re: [PATCH v3 3/4] clk: tegra: MBIST work around for Tegra210

Jon Hunter
2018-01-25T10:19:08Z

On 25/01/18 09:02, Peter De Schrijver wrote:
> On Wed, Jan 24, 2018 at 09:59:56PM +0000, Jon Hunter wrote:

...

>>> +void tegra210_clk_handle_mbist_war(unsigned int id)
>>> +{
>>> + int err;
>>> + struct tegra210_domain_mbist_war *mbist_war;
>>> +
>>> + if (id >= ARRAY_SIZE(tegra210_pg_mbist_war)) {
>>> + WARN(1, "unknown domain id in MBIST WAR handler\n");
>>> + return;
>>> + }
>>> +
>>> + mbist_war = &tegra210_pg_mbist_war[id];
>>> + if (!mbist_war->handle_lvl2_ovr)
>>> + return;
>>> +
>>> + err = mbist_war->handle_lvl2_ovr(mbist_war);
>>
>> Why not move the clk_bulk_prepare_enable/disable_unprepare and
>> mutex_lock/unlock functions into this function around the call to
>> ->handle_lvl2_ovr to save the duplication of that code in each of the
>> war functions?
>>
>
> This could be done yes.
>
>>> + WARN(err < 0, "error handling MBIST WAR for domain: %d\n", id);
>>> +}
>>
>> I think that the above function should return an error and we should let
>> the power-domain power-on fail.
>>
>
> This would only be useful if the user (tegra_powergate_power_up) would do
> rollback. I don't think that's done correctly today.

It does and so I think that we should return an error.

>>> +
>>> +
>>> void tegra210_put_utmipll_in_iddq(void)
>>> {
>>> u32 reg;
>>> @@ -3163,6 +3500,40 @@ static int tegra210_reset_deassert(unsigned long id)
>>> return 0;
>>> }
>>>
>>> +static void tegra210_mbist_clk_init(void)
>>> +{
>>> + int i, j;
>>> +
>>> + for (i = 0; i < ARRAY_SIZE(tegra210_pg_mbist_war); i++) {
>>> + int num_clks = tegra210_pg_mbist_war[i].num_clks;
>>> + struct clk_bulk_data *clk_data;
>>> +
>>> + if (!num_clks)
>>> + continue;
>>> +
>>> + clk_data = kmalloc_array(num_clks, sizeof(*clk_data),
>>> + GFP_KERNEL);
>>> + if (WARN(!clk_data,
>>> + "no space for MBIST WAR clk array for %d\n", i)) {
>>> + tegra210_pg_mbist_war[i].handle_lvl2_ovr = NULL;
>>> + continue;
>>> + }
>>
>> Printing error messages on memory allocation failures are not needed and
>> have been removed from various drivers. So lets no add any error
>> messages or warnings here.
>>
>> Also I think that we should just return an error here and not bother
>> continuing as there is no point.

So maybe here just ...

if (WARN_ON(!clk_data))
return -ENOMEM;

>>> +
>>> + tegra210_pg_mbist_war[i].clks = clk_data;
>>
>> I think that you should only populate this when all the clocks have been
>> initialised correctly. You could then use this to check the clocks have
>> been setup correctly when executing the war.
>>
>
> For some domains no extra clocks are needed (ie the clocks enabled by the
> power domain driver are enough). So an extra flag would be needed then.

Yes but you have num_clks to detect if a domain has extra clocks. So you
can use both of these to detect if the clocks are setup correctly. Right?

>>> + for (j = 0; j < num_clks; j++) {
>>> + int clk_id = tegra210_pg_mbist_war[i].clk_init_data[j];
>>> + struct clk *clk = clks[clk_id];
>>> +
>>> + if (IS_ERR(clk)) {
>>> + clk_data[j].clk = NULL;
>>> + WARN(1, "clk_id: %d\n", clk_id);
>>
>> I think that we should return an error here.
>>
>
> I don't think letting clock init fail because of this, is a good idea. Too
> many things rely on working clocks.

It should never fail and if it does something is badly broken.

Maybe what we could do ...

if (WARN_ON(IS_ERR(clk))) {
tegra210_pg_mbist_war[i].clks = NULL;
break;
}

clk_data[j].clk = clk;

Then we can check in tegra210_clk_handle_mbist_war() ...

if (mbist_war->num_clks && !mbist_war.clks)
return -ENODEV;

Does that work?

>>> + } else {
>>> + clk_data[j].clk = clk;
>>> + }
>>> + }
>>> + }
>>> +}
>>> +
>>> /**
>>> * tegra210_clock_init - Tegra210-specific clock initialization
>>> * @np: struct device_node * of the DT node for the SoC CAR IP block
>>> @@ -3197,6 +3568,24 @@ static void __init tegra210_clock_init(struct device_node *np)
>>> return;
>>> }
>>>
>>> + ape_base = ioremap(TEGRA210_APE_BASE, 256*1024);
>>> + if (!ape_base) {
>>> + pr_err("ioremap tegra210 APE failed\n");
>>> + return;
>>> + }
>>> +
>>> + dispa_base = ioremap(TEGRA210_DISPA_BASE, 256*1024);
>>> + if (!dispa_base) {
>>> + pr_err("ioremap tegra210 DISPA failed\n");
>>> + return;
>>> + }
>>> +
>>> + vic_base = ioremap(TEGRA210_VIC_BASE, 256*1024);
>>> + if (!vic_base) {
>>> + pr_err("ioremap tegra210 VIC failed\n");
>>> + return;
>>> + }
>>> +
>>> clks = tegra_clk_init(clk_base, TEGRA210_CLK_CLK_MAX,
>>> TEGRA210_CAR_BANK_COUNT);
>>> if (!clks)
>>> @@ -3233,6 +3622,8 @@ static void __init tegra210_clock_init(struct device_node *np)
>>> tegra_add_of_provider(np);
>>> tegra_register_devclks(devclks, ARRAY_SIZE(devclks));
>>>
>>> + tegra210_mbist_clk_init();
>>> +
>>
>> Maybe add a print here if the mbist init fails and return. I understand
>> it may not be a critical failure but it should never fail.
>>
>
> You mean have the entire clock init fail and undo all the clock registrations?
> That seems overkill to me. Returning early would only prevent some sleep states
> from working because tegra_cpu_car_ops will not be initialized then. So I would
> do a warning then.

I don't think it is necessary to undo it. Ok, don't worry about
returning an error here, the warnings should be sufficient.

Cheers
Jon

--
nvpublic