linux-kernel - Re: [PATCH] soc: bcm: brcmstb: Remove bare-metal ARM suspend/resume code

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Message-ID: <35dc0b00-0de4-f1b4-8d43-7efd181e7dbf@gmail.com>
Date:   Mon, 27 Feb 2023 10:38:51 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        linux-arm-kernel@...r.kernel.org
Cc:     drv@...lo.com, ssengar@...rosoft.com,
        kumarpraveen@...ux.microsoft.com, christophe.jaillet@...adoo.fr,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Miaoqian Lin <linmq006@...il.com>, Liang He <windhl@....com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Julia Lawall <Julia.Lawall@...ia.fr>,
        open list <linux-kernel@...r.kernel.org>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] soc: bcm: brcmstb: Remove bare-metal ARM suspend/resume
 code



On 2/27/2023 10:36 AM, Guilherme G. Piccoli wrote:
> On 24/02/2023 18:52, Florian Fainelli wrote:
>> Since 2018 these platforms have supported entry via the ARM Trusted
>> Firmware using the standard PSCI SYSTEM_SUSPEND function calls. Remove
>> this legacy code.
>>
>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>> [...]
>> -/*
>> - * The AON is a small domain in the SoC that can retain its state across
>> - * various system wide sleep states and specific reset conditions; the
>> - * AON DATA RAM is a small RAM of a few words (< 1KB) which can store
>> - * persistent information across such events.
>> - *
>> - * The purpose of the below panic notifier is to help with notifying
>> - * the bootloader that a panic occurred and so that it should try its
>> - * best to preserve the DRAM contents holding that buffer for recovery
>> - * by the kernel as opposed to wiping out DRAM clean again.
>> - *
>> - * Reference: comment from Florian Fainelli, at
>> - * https://lore.kernel.org/lkml/781cafb0-8d06-8b56-907a-5175c2da196a@gmail.com
>> - */
>> -static int brcmstb_pm_panic_notify(struct notifier_block *nb,
>> -		unsigned long action, void *data)
>> -{
>> -	writel_relaxed(BRCMSTB_PANIC_MAGIC, ctrl.aon_sram + AON_REG_PANIC);
>> -
>> -	return NOTIFY_DONE;
>> [...]
> 
> Hi Florian, thanks for the clean-up!
> 
> I'm curious with the above panic notifier - is it not necessary when
> PSCI is used?

This is a bit of long story, but no, it is not necessary.
-- 
Florian