linux-kernel - Re: [SHDCI] Heavy (thousands) DMA leaks

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Date:	Mon, 3 Aug 2015 11:39:34 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	Chen Bough <Haibo.Chen@...escale.com>
Cc:	Ulf Hansson <ulf.hansson@...aro.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [SHDCI] Heavy (thousands) DMA leaks

Hi,

On 08/03/2015, 11:30 AM, Chen Bough wrote:
> I carefully review my patch, all the DMA memory mapped in sdhci_pre_req() is unmapped in sdhci_post_req.

I suspect 'host_cookie' or 'next' handling is bad somewhere. But I don't
know...

> Can you provide the method of your testing DMA leaks?

boot kernel with CONFIG_DMA_API_DEBUG
insert the card
mount it
rsync from the card ~200 MB
umount it
unload the sdhci driver
the leak warning is reported

I am not sure whether suspend-resume is needed after the first step.

> You said over 4000 leaked mappings during one card transfer, if true, 
> We can't map any dma memory after some sd transfer, do you meet this?

Yes, I see:
sdhci-pci 0000:02:00.0: swiotlb buffer is full (sz: 65536 bytes)
after some time. The driver falls back to non-DMA transfers after that.
It also generates a warning about that:
WARNING: CPU: 0 PID: 0 at drivers/mmc/host/sdhci.c:857
sdhci_prepare_data+0x8ec/0x900 [sdhci]()

thanks,
-- 
js
suse labs
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