linux-kernel - Re: [PATCH v2 08/10] clk: renesas: rzg2l-cpg: Add suspend/resume support for power domains

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Message-ID: <00b6c73b-d57f-4520-b1af-d2ad2a88240d@tuxon.dev>
Date: Wed, 10 Apr 2024 13:31:35 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: mturquette@...libre.com, sboyd@...nel.org, robh@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 magnus.damm@...il.com, linux-renesas-soc@...r.kernel.org,
 linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH v2 08/10] clk: renesas: rzg2l-cpg: Add suspend/resume
 support for power domains

Hi, Geert,

Sorry for replying that late to this one.

On 18.03.2024 18:48, Geert Uytterhoeven wrote:
> Hi Claudiu,
> 
> On Thu, Mar 7, 2024 at 3:07 PM Claudiu <claudiu.beznea@...on.dev> wrote:
>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> RZ/G3S supports deep sleep states that it can reach with the help of the
>> TF-A.
>>
>> RZ/G3S has a few power domains (e.g. GIC) that need to be always-on while
>> Linux is running. These domains are initialized (and powered on) when
>> clock driver is probed.
>>
>> As the TF-A takes control at the very last(suspend)/first(resume)
>> phase of configuring the deep sleep state, it can do it's own settings on
>> power domains.
>>
>> Thus, to restore the proper Linux state, add rzg2l_cpg_resume() which
>> powers on the always-on domains and rzg2l_cpg_complete() which activates
>> the power down mode for the IPs selected through CPG_PWRDN_IP{1, 2}.
>>
>> Along with it, added the suspend_check member to the RZ/G2L power domain
>> data structure whose purpose is to checks if a domain can be powered off
>> while the system is going to suspend. This is necessary for the serial
>> console domain which needs to be powered on if no_console_suspend is
>> available in bootargs.
>>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>> ---
>>
>> Changes in v2:
>> - none; this patch is new
> 
> Thanks for your patch!
> 
>> --- a/drivers/clk/renesas/rzg2l-cpg.c
>> +++ b/drivers/clk/renesas/rzg2l-cpg.c
>> @@ -1700,6 +1719,8 @@ static int __init rzg2l_cpg_pd_setup(struct rzg2l_cpg_pd *pd, bool always_on)
>>         } else {
>>                 pd->genpd.power_on = rzg2l_cpg_power_on;
>>                 pd->genpd.power_off = rzg2l_cpg_power_off;
>> +               if (flags & RZG2L_PD_F_CONSOLE)
> 
> I think this should be replaced by some dynamic check, cfr. my comments
> on PATCH 9/10.

I agree.

> 
>> +                       pd->suspend_check = rzg2l_pd_suspend_check_console;
>>                 governor = &simple_qos_governor;
>>         }
>>
> 
>> @@ -1890,9 +1911,43 @@ static int __init rzg2l_cpg_probe(struct platform_device *pdev)
>>         if (error)
>>                 return error;
>>
>> +       dev_set_drvdata(dev, priv);
>> +
>>         return 0;
>>  }
>>
>> +static int rzg2l_cpg_resume(struct device *dev)
>> +{
>> +       struct rzg2l_cpg_priv *priv = dev_get_drvdata(dev);
>> +       const struct rzg2l_cpg_info *info = priv->info;
>> +
>> +       /* Power on always ON domains. */
>> +       for (unsigned int i = 0; i < info->num_pm_domains; i++) {
>> +               if (info->pm_domains[i].flags & RZG2L_PD_F_ALWAYS_ON) {
> 
> If you would check "priv-domains[i].flags & GENPD_FLAG_ALWAYS_ON"
> instead, I think you can make r9a08g045_pm_domains[] __initconst.
> You may need to make a copy of the name for pd->genpd.name, though.

I wanted to avoid this copy.

> 
>> +                       int ret = rzg2l_cpg_power_on(priv->domains[i]);
> 
> I assume you are sure none of these domains are enabled by TF/A after
> system resume, or by the pmdomain core code?

Out of TF-A the MSTOP and PWRDN bits for these ones are set and setting
CPG_PWRDN_MSTOP though rzg2l_cpg_complete() leads to system being blocked.
It is the same as in booting case exlained in cover letter.

"the DDR, TZCDDR, OTFDE_DDR were also added, to avoid system being blocked
due to the following lines of code from patch 6/10.

+       /* Prepare for power down the BUSes in power down mode. */
+       if (info->pm_domain_pwrdn_mstop)
+               writel(CPG_PWRDN_MSTOP_ENABLE, priv->base + CPG_PWRDN_MSTOP);

Domain IDs were added to all SoC specific bindings.
"

The PM domain core code doesn't touch these domains while resuming as of my
checkings.

Thank you,
Claudiu Beznea

> 
> Gr{oetje,eeting}s,
> 
>                         Geert
>