linux-kernel - Re: [PATCH 1/3] ASoC: samsung: pass DMA channels as pointers

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Message-ID: <25607973.ZAWqqjj8F4@wuerfel>
Date:	Tue, 17 Nov 2015 11:24:24 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Mark Brown <broonie@...nel.org>, alsa-devel@...a-project.org,
	Liam Girdwood <lgirdwood@...il.com>,
	Heiko Stuebner <heiko@...ech.de>,
	Kukjin Kim <kgene@...nel.org>,
	Sangbeom Kim <sbkim73@...sung.com>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Vinod Koul <vinod.koul@...el.com>
Subject: Re: [PATCH 1/3] ASoC: samsung: pass DMA channels as pointers

On Tuesday 17 November 2015 10:16:36 Krzysztof Kozlowski wrote:
> On 14.11.2015 02:22, Arnd Bergmann wrote:
> > ARM64 allmodconfig produces a bunch of warnings when building the
> > samsung ASoC code:
> > 
> > sound/soc/samsung/dmaengine.c: In function 'samsung_asoc_init_dma_data':
> > sound/soc/samsung/dmaengine.c:53:32: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
> >    playback_data->filter_data = (void *)playback->channel;
> > sound/soc/samsung/dmaengine.c:60:31: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
> >    capture_data->filter_data = (void *)capture->channel;
> > 
> > We could easily shut up the warning by adding an intermediate cast,
> > but there is a bigger underlying problem: The use of IORESOURCE_DMA
> > to pass data from platform code to device drivers is dubious to start
> > with, as what we really want is a pointer that can be passed into
> > a filter function.
> > 
> > Note that on s3c64xx, the pl08x DMA data is already a pointer, but
> > gets cast to resource_size_t so we can pass it as a resource, and it
> > then gets converted back to a pointer. In contrast, the data we pass
> > for s3c24xx is an index into a device specific table, and we artificially
> > convert that into a pointer for the filter function.
> > 
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> 
> The patch looks good. I have only two questions below.

Thanks for taking a look!

> > @@ -1338,11 +1325,8 @@ static int samsung_i2s_probe(struct platform_device *pdev)
> >               sec_dai->dma_playback.dma_addr = regs_base + I2STXDS;
> >               sec_dai->dma_playback.ch_name = "tx-sec";
> >  
> > -             if (!np) {
> > -                     res = platform_get_resource(pdev, IORESOURCE_DMA, 2);
> > -                     if (res)
> > -                             sec_dai->dma_playback.channel = res->start;
> > -             }
> > +             if (!np)
> > +                     sec_dai->dma_playback.slave = i2s_pdata->dma_play_sec;
> 
> I cannot this resource in original patch nor setting the 'dma_play_sec'
> part. I guess this does not really matter as newer platforms were
> converted to DT so 'np' will be set, right?

Yes, that sounds correct.

> > @@ -367,12 +367,6 @@ static int spdif_probe(struct platform_device *pdev)
> >  
> >       dev_dbg(&pdev->dev, "Entered %s\n", __func__);
> >  
> > -     dma_res = platform_get_resource(pdev, IORESOURCE_DMA, 0);
> > -     if (!dma_res) {
> > -             dev_err(&pdev->dev, "Unable to get dma resource.\n");
> > -             return -ENXIO;
> > -     }
> > -
> >       mem_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> >       if (!mem_res) {
> >               dev_err(&pdev->dev, "Unable to get register resource.\n");
> > @@ -432,7 +426,7 @@ static int spdif_probe(struct platform_device *pdev)
> >  
> >       spdif_stereo_out.dma_size = 2;
> >       spdif_stereo_out.dma_addr = mem_res->start + DATA_OUTBUF;
> > -     spdif_stereo_out.channel = dma_res->start;
> > +     spdif_stereo_out.slave = spdif_pdata->dma_playback;
> >  
> >       spdif->dma_playback = &spdif_stereo_out;
> 
> No one sets ioresources and pdata for spdif device. No in-kernel board
> files for it?

Hmm, probably also a missing conversion to devicetree. The symbol used to be 

 config SND_SOC_SAMSUNG_SMDK_SPDIF
        tristate "SoC S/PDIF Audio support for SMDK"
-       depends on SND_SOC_SAMSUNG && (MACH_SMDKC100 || MACH_SMDKC110 || MACH_SMDKV210 || MACH_SMDKV310 || MACH_SMDK4212)
+       depends on SND_SOC_SAMSUNG
        select SND_SAMSUNG_SPDIF

We still support all four of the above boards, but they are all DT-only
and neither spdif.c nor smdk-spdif.c ever gained DT support. Is there
anything I should change in this patch for this?

	Arnd
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