linux-kernel - Re: [PATCH] nvmem: brcm_nvram: store a copy of NVRAM content

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Date:   Fri, 15 Sep 2023 09:25:48 +0200
From:   Rafał Miłecki <rafal@...ecki.pl>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Rafał Miłecki <zajec5@...il.com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Arınç ÜNAL <arinc.unal@...nc9.com>,
        Florian Fainelli <florian.fainelli@...adcom.com>,
        Scott Branden <scott.branden@...adcom.com>
Subject: Re: [PATCH] nvmem: brcm_nvram: store a copy of NVRAM content

On 2023-09-14 23:26, Florian Fainelli wrote:
> On 9/13/23 23:49, Rafał Miłecki wrote:
>> From: Rafał Miłecki <rafal@...ecki.pl>
>> 
>> This driver uses MMIO access for reading NVRAM from a flash device.
>> Underneath there is a flash controller that reads data and provides
>> mapping window.
>> 
>> Using MMIO interface affects controller configuration and may break 
>> real
>> controller driver. It was reported by multiple users of devices with
>> NVRAM stored on NAND.
>> 
>> Modify driver to read & cache all NVRAM content during init and use 
>> that
>> copy to provide NVMEM data when requested.
>> 
>> Link: 
>> https://lore.kernel.org/linux-mtd/CACna6rwf3_9QVjYcM+847biTX=K0EoWXuXcSMkJO1Vy_5vmVqA@mail.gmail.com/
>> Cc: Arınç ÜNAL <arinc.unal@...nc9.com>
>> Cc: Florian Fainelli <florian.fainelli@...adcom.com>
>> Cc: Scott Branden <scott.branden@...adcom.com>
>> Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
>> ---
> [snip]
>> -	priv->base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
>> -	if (IS_ERR(priv->base))
>> -		return PTR_ERR(priv->base);
>> +	base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
>> +	if (IS_ERR(base))
>> +		return PTR_ERR(base);
>> +
>> +	priv->size = resource_size(res);
>> +
>> +	priv->data = devm_kzalloc(dev, priv->size, GFP_KERNEL);
> 
> These can conceivably quite big data structures, how about using 
> kvmalloc()?

Good idea.

Actual NVRAM data usually doesn't take much space, but it reserves quite 
a lot and we need all of that to full expose NVMEM device content.

-- 
Rafał Miłecki