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soc: bcm: brcmstb: Document panic notifier action and remove useless header

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The panic notifier of this driver is very simple code-wise, just a
memory write to a special position with some numeric code. But this
is not clear from the semantic point-of-view, and there is no public
documentation about that either.

After discussing this in the mailing-lists [0] and having Florian
explained it very well, document that in the code for the future
generations asking the same questions. Also, while at it, remove
a useless header.

[0] https://lore.kernel.org/lkml/781cafb0-8d06-8b56-907a-5175c2da196a@gmail.com

Cc: Brian Norris <computersforpeace@gmail.com>
Cc: Doug Berger <opendmb@gmail.com>
Cc: Justin Chen <justinpopo6@gmail.com>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Markus Mayer <mmayer@broadcom.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Link: https://lore.kernel.org/r/20220719195325.402745-5-gpiccoli@igalia.com
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
This commit is contained in:
Guilherme G. Piccoli 2022-07-19 16:53:17 -03:00 committed by Florian Fainelli
parent 568035b01c
commit 751c3e19d0
1 changed files with 14 additions and 2 deletions
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16
drivers/soc/bcm/brcmstb/pm/pm-arm.c
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@ -25,7 +25,6 @@
#include <linux/kernel.h>
#include <linux/memblock.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/panic_notifier.h>
@ -664,7 +663,20 @@ static void __iomem *brcmstb_ioremap_match(const struct of_device_id *matches,
return of_io_request_and_map(dn, index, dn->full_name);
}
/*
* 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)
{