netdev - Re: [PATCH v1] net: stmmac: Free rx

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Date:	Wed, 25 Nov 2015 16:13:08 +0100
From:	Giuseppe CAVALLARO <peppe.cavallaro@...com>
To:	David Miller <davem@...emloft.net>, <zhengsq@...k-chips.com>
CC:	<linux-kernel@...r.kernel.org>,
	<linux-rockchip@...ts.infradead.org>, <netdev@...r.kernel.org>,
	<dianders@...gle.com>
Subject: Re: [PATCH v1] net: stmmac: Free rx_skbufs before realloc

Hello

On 11/24/2015 7:09 PM, David Miller wrote:
> From: Shunqian Zheng <zhengsq@...k-chips.com>
> Date: Sun, 22 Nov 2015 16:44:18 +0800
>
>> From: ZhengShunQian <zhengsq@...k-chips.com>
>>
>> The init_dma_desc_rings() may realloc the rx_skbuff[] when
>> suspend and resume. This patch free the rx_skbuff[] before
>> reallocing memory.
>>
>> Signed-off-by: ZhengShunQian <zhengsq@...k-chips.com>
>
> This isn't really the right way to fix this.
>
> I see two reasonable approaches:
>
> 1) suspend liberates the RX ring, although this approach is less
>     desirable
>
> 2) resume doesn't try to allocate already populated RX ring
>     entries
>
> Freeing the whole RX ring just to allocate it again immediately
> makes no sense at all and is wasteful work.

This is a bug in this driver version that, to be honest, we fixed with
the first approach on STi kernel.
The patch just called the dma_free_rx_skbufs(priv) in the suspend.
I can give you this patch that is tested on my side too.
But! I do think we should move on second approach.
Indeed, also on ST platforms, when we play with suspend states
the DDR although in self-refresh the data are not lost at all.
No reason to free and reallocate all in suspend/resume.
I can test that and then provide another patch to this mailing list
asap.

Let me know.
peppe

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