netdev - Re: regression in ath10k dma allocation

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Message-ID: <acd7a4b0-fde8-1aa2-af07-2b469e5d5ca7@mni.thm.de>
Date:   Mon, 19 Aug 2019 00:38:38 +0200
From:   Tobias Klausmann <tobias.johannes.klausmann@....thm.de>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Nicolin Chen <nicoleotsuka@...il.com>,
        Christoph Hellwig <hch@....de>, kvalo@...eaurora.org,
        davem@...emloft.net, ath10k@...ts.infradead.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, m.szyprowski@...sung.com,
        robin.murphy@....com, iommu@...ts.linux-foundation.org,
        tobias.klausmann@...enet.de
Subject: Re: regression in ath10k dma allocation


On 18.08.19 05:13, Hillf Danton wrote:
> On Sat, 17 Aug 2019 00:42:48 +0200 Tobias Klausmann wrote:
>> Hi Nicolin,
>>
>> On 17.08.19 00:25, Nicolin Chen wrote:
>>> Hi Tobias
>>>
>>> On Fri, Aug 16, 2019 at 10:16:45PM +0200, Tobias Klausmann wrote:
>>>>> do you have CONFIG_DMA_CMA set in your config?  If not please make sure
>>>>> you have this commit in your testing tree, and if the problem still
>>>>> persists it would be a little odd and we'd have to dig deeper:
>>>>>
>>>>> commit dd3dcede9fa0a0b661ac1f24843f4a1b1317fdb6
>>>>> Author: Nicolin Chen <nicoleotsuka@...il.com>
>>>>> Date:   Wed May 29 17:54:25 2019 -0700
>>>>>
>>>>>        dma-contiguous: fix !CONFIG_DMA_CMA version of dma_{alloc, free}_contiguous()
>>>> yes CONFIG_DMA_CMA is set (=y, see attached config), the commit you mention
>>>> above is included, if you have any hints how to go forward, please let me
>>>> know!
>>> For CONFIG_DMA_CMA=y, by judging the log with error code -12, I
>>> feel this one should work for you. Would you please check if it
>>> is included or try it out otherwise?
>>>
>>> dma-contiguous: do not overwrite align in dma_alloc_contiguous()
>>> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=c6622a425acd1d2f3a443cd39b490a8777b622d7
>>
>> Thanks for the hint, yet the commit is included and does not fix the
>> problem!
>>
Hi Hillf,

i just tested you first hunk (which comes from kernel/dma/direct.c if 
i'm not mistaken), it did not compile on its own, yet with a tiny bit of 
work it did, and it does indeed solve the regression. But if using that 
is the "right" way to do it, not sure, but its not on me to decide.

Anyway: Thanks for the hint,

Tobias


> Hi Tobias
>
> Two minor diffs below in hope that they might make sense.
>
> 1, fallback unless dma coherent ok.
>
> --- a/kernel/dma/contiguous.c
> +++ b/kernel/dma/contiguous.c
> @@ -246,6 +246,10 @@ struct page *dma_alloc_contiguous(struct
>   		size_t cma_align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);
>   
>   		page = cma_alloc(cma, count, cma_align, gfp & __GFP_NOWARN);
> +		if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
> +			dma_free_contiguous(dev, page, size);
> +			page = NULL;
> +		}
>   	}
>   
>   	/* Fallback allocation of normal pages */
> --
>
> 2, cleanup: cma unless contiguous
>
> --- a/kernel/dma/contiguous.c
> +++ b/kernel/dma/contiguous.c
> @@ -234,18 +234,13 @@ struct page *dma_alloc_contiguous(struct
>   	size_t count = PAGE_ALIGN(size) >> PAGE_SHIFT;
>   	size_t align = get_order(PAGE_ALIGN(size));
>   	struct page *page = NULL;
> -	struct cma *cma = NULL;
> -
> -	if (dev && dev->cma_area)
> -		cma = dev->cma_area;
> -	else if (count > 1)
> -		cma = dma_contiguous_default_area;
>   
>   	/* CMA can be used only in the context which permits sleeping */
> -	if (cma && gfpflags_allow_blocking(gfp)) {
> +	if (count > 1 && gfpflags_allow_blocking(gfp)) {
>   		size_t cma_align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);
>   
> -		page = cma_alloc(cma, count, cma_align, gfp & __GFP_NOWARN);
> +		page = cma_alloc(dev_get_cma_area(dev), count, cma_align,
> +							gfp & __GFP_NOWARN);
>   		if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
>   			dma_free_contiguous(dev, page, size);
>   			page = NULL;
> --
>