From: Arnd Bergmann <arnd@arndb.de>
To: Robert Jarzmik <robert.jarzmik@free.fr>
Cc: Daniel Mack <daniel@zonque.org>,
Haojian Zhuang <haojian.zhuang@gmail.com>,
Vinod Koul <vinod.koul@intel.com>,
Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
Liam Girdwood <lgirdwood@gmail.com>,
Mark Brown <broonie@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
alsa-devel@alsa-project.org
Subject: Re: [PATCH 14/15] ARM: pxa: change SSP devices allocation
Date: Tue, 3 Apr 2018 17:53:25 +0200 [thread overview]
Message-ID: <CAK8P3a1ko=YEwR2VOahH0OWHfeOyWAzDYah4DSohBcvTNq_MKQ@mail.gmail.com> (raw)
In-Reply-To: <87lge4485x.fsf@belgarion.home>
On Tue, Apr 3, 2018 at 5:32 PM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
> Arnd Bergmann <arnd@arndb.de> writes:
>
> chop chop ... removed several mail recipients to leave only the ASoC / PXA
> subset ...
>
>> On Mon, Apr 2, 2018 at 4:26 PM, Robert Jarzmik <robert.jarzmik@free.fr> wrote:
>>
>>>
>>> +static struct pxa_ssp_info pxa_ssp_infos[] = {
>>> + { .dma_chan_rx_name = "ssp1_rx", .dma_chan_tx_name = "ssp1_tx", },
>>> + { .dma_chan_rx_name = "ssp1_rx", .dma_chan_tx_name = "ssp1_tx", },
>>> + { .dma_chan_rx_name = "ssp2_rx", .dma_chan_tx_name = "ssp2_tx", },
>>> + { .dma_chan_rx_name = "ssp2_rx", .dma_chan_tx_name = "ssp2_tx", },
>>> + { .dma_chan_rx_name = "ssp3_rx", .dma_chan_tx_name = "ssp3_tx", },
>>> + { .dma_chan_rx_name = "ssp3_rx", .dma_chan_tx_name = "ssp3_tx", },
>>> + { .dma_chan_rx_name = "ssp4_rx", .dma_chan_tx_name = "ssp4_tx", },
>>> + { .dma_chan_rx_name = "ssp4_rx", .dma_chan_tx_name = "ssp4_tx", },
>>> +};
>>
>> This part looks odd to me, you're adding an extra level of indirection to
>> do two stages of lookups in some form of platform data.
> That's unfortunately right.
>
>> Why can't you just always use "rx" and "tx" as the names here?
> Well I couldn't. I'll explain you why, and maybe you'll find a better solution.
>
> That all is related to how ASoC and SSP interact.
> If I remember correctly, here is how it works :
> - the DMA channel is requested in sound/arm/pxa2xx-pcm-lib.c:128
> return snd_dmaengine_pcm_open(
> substream, dma_request_slave_channel(rtd->platform->dev,
> The trick is that the device here is _not_ the SSP one, it's if memory serves
> me well the pxa-pcm-audio one.
>
> As a consequence, the device cannot be used to differenciate which SSP
> exactly is providing the sound samples stream. This information is
> nevertheless required to choose the correct requestor line, which is a 1-to-1
> match to the SSP port.
>
> The indirection in the channel name is used to choose the correct requestor
> line for a given SSP port providing the samples.
>
> It also must be underlined that this dma request serves both AC97 and SSP as
> sample providers.
I'm still unable to follow through that code, but I understand now that
the device you pass to dma_request_slave_channel() is not the one
we'd like it to be here.
Where exactly does that call to dma_request_chan() happen? Is this
the one in dmaengine_pcm_new()? Could we perhaps put a
pointer to the SSP device into snd_dmaengine_dai_dma_data?
Arnd
next prev parent reply other threads:[~2018-04-03 15:53 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-02 14:26 [PATCH 00/15] ARM: pxa: switch to DMA slave maps Robert Jarzmik
2018-04-02 14:26 ` [PATCH 01/15] dmaengine: pxa: use a dma slave map Robert Jarzmik
[not found] ` <87604kz7mu.fsf@belgarion.home>
2018-04-22 6:13 ` Vinod Koul
2018-04-02 14:26 ` [PATCH 02/15] ARM: pxa: add " Robert Jarzmik
2018-04-03 6:51 ` Arnd Bergmann
2018-04-03 15:18 ` Robert Jarzmik
2018-04-03 15:39 ` Arnd Bergmann
2018-04-03 20:19 ` Robert Jarzmik
2018-04-04 10:18 ` Arnd Bergmann
2018-04-04 19:21 ` Robert Jarzmik
2018-04-02 14:26 ` [PATCH 03/15] mmc: pxamci: remove the dmaengine compat need Robert Jarzmik
2018-04-02 14:26 ` [PATCH 04/15] media: pxa_camera: " Robert Jarzmik
2018-04-21 19:27 ` Robert Jarzmik
2018-04-22 11:06 ` Hans Verkuil
2018-04-22 11:06 ` Hans Verkuil
2018-05-04 19:29 ` Mauro Carvalho Chehab
2018-04-02 14:26 ` [PATCH 05/15] mtd: nand: pxa3xx: " Robert Jarzmik
2018-05-18 21:31 ` Daniel Mack
2018-05-23 21:54 ` Daniel Mack
2018-04-02 14:26 ` [PATCH 06/15] net: smc911x: " Robert Jarzmik
2018-04-02 14:26 ` [PATCH 07/15] net: smc91x: " Robert Jarzmik
2018-04-02 14:26 ` [PATCH 08/15] ASoC: pxa: " Robert Jarzmik
2018-04-12 15:26 ` Mark Brown
2018-04-12 16:55 ` Robert Jarzmik
2018-04-02 14:26 ` [PATCH 09/15] net: irda: pxaficp_ir: " Robert Jarzmik
2018-04-21 19:30 ` Robert Jarzmik
2018-04-23 8:37 ` Greg Kroah-Hartman
2018-04-02 14:26 ` [PATCH 10/15] ata: pata_pxa: " Robert Jarzmik
2018-04-21 19:32 ` Robert Jarzmik
2018-04-24 11:04 ` Bartlomiej Zolnierkiewicz
2018-04-02 14:26 ` [PATCH 11/15] dmaengine: pxa: document pxad_param Robert Jarzmik
2018-04-02 14:26 ` [PATCH 12/15] dmaengine: pxa: make the filter function internal Robert Jarzmik
2018-04-02 16:25 ` kbuild test robot
2018-04-02 16:35 ` kbuild test robot
2018-04-03 7:13 ` Arnd Bergmann
2018-04-02 14:26 ` [PATCH 13/15] ARM: pxa: remove the DMA IO resources Robert Jarzmik
2018-04-02 14:26 ` [PATCH 14/15] ARM: pxa: change SSP devices allocation Robert Jarzmik
2018-04-03 7:06 ` Arnd Bergmann
2018-04-03 15:32 ` Robert Jarzmik
2018-04-03 15:53 ` Arnd Bergmann [this message]
2018-04-05 6:51 ` Robert Jarzmik
2018-04-05 7:29 ` Arnd Bergmann
2018-04-08 12:16 ` Robert Jarzmik
2018-04-02 14:26 ` [PATCH 15/15] ARM: pxa: change SSP DMA channels allocation Robert Jarzmik
2018-04-02 18:46 ` kbuild test robot
2018-04-03 7:15 ` [PATCH 00/15] ARM: pxa: switch to DMA slave maps Arnd Bergmann
2018-04-03 15:08 ` Ulf Hansson
2018-04-04 19:49 ` Robert Jarzmik
2018-04-04 19:56 ` Boris Brezillon
2018-04-05 6:29 ` Ulf Hansson
2018-04-05 6:50 ` Arnd Bergmann
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