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Subject: Re: [PATCH] ASoC: fsl: imx-pcm-dma: Don't request dma channel in
 probe
From:   Lucas Stach <l.stach@pengutronix.de>
To:     Shengjiu Wang <shengjiu.wang@gmail.com>
Cc:     Shengjiu Wang <shengjiu.wang@nxp.com>,
        Timur Tabi <timur@kernel.org>,
        Nicolin Chen <nicoleotsuka@gmail.com>,
        Xiubo Li <Xiubo.Lee@gmail.com>,
        Fabio Estevam <festevam@gmail.com>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>, perex@perex.cz,
        Takashi Iwai <tiwai@suse.com>, shawnguo@kernel.org,
        s.hauer@pengutronix.de, kernel@pengutronix.de, linux-imx@nxp.com,
        sumit.semwal@linaro.org, Linux-ALSA <alsa-devel@alsa-project.org>,
        linuxppc-dev@lists.ozlabs.org,
        linux-arm-kernel@lists.infradead.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
        linaro-mm-sig@lists.linaro.org
Date:   Wed, 20 May 2020 11:42:32 +0200
In-Reply-To: <CAA+D8APhHvA39wmCayeCsAEKmOJ0n7qOQiT1tZmFHr4+yASgTw@mail.gmail.com>
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Am Mittwoch, den 20.05.2020, 16:20 +0800 schrieb Shengjiu Wang:
> Hi
> 
> On Tue, May 19, 2020 at 6:04 PM Lucas Stach <l.stach@pengutronix.de> wrote:
> > Am Dienstag, den 19.05.2020, 17:41 +0800 schrieb Shengjiu Wang:
> > > There are two requirements that we need to move the request
> > > of dma channel from probe to open.
> > 
> > How do you handle -EPROBE_DEFER return code from the channel request if
> > you don't do it in probe?
> 
> I use the dma_request_slave_channel or dma_request_channel instead
> of dmaengine_pcm_request_chan_of. so there should be not -EPROBE_DEFER
> return code.

This is a pretty weak argument. The dmaengine device might probe after
you try to get the channel. Using a function to request the channel
that doesn't allow you to handle probe deferral is IMHO a bug and
should be fixed, instead of building even more assumptions on top of
it.

> > > - When dma device binds with power-domains, the power will
> > > be enabled when we request dma channel. If the request of dma
> > > channel happen on probe, then the power-domains will be always
> > > enabled after kernel boot up,  which is not good for power
> > > saving,  so we need to move the request of dma channel to .open();
> > 
> > This is certainly something which could be fixed in the dmaengine
> > driver.
> 
> Dma driver always call the pm_runtime_get_sync in
> device_alloc_chan_resources, the device_alloc_chan_resources is
> called when channel is requested. so power is enabled on channel
> request.

So why can't you fix the dmaengine driver to do that RPM call at a
later time when the channel is actually going to be used? This will
allow further power savings with other slave devices than the audio
PCM.

Regards,
Lucas

> > > - With FE-BE case, if the dma channel is requested in probe,
> > > then there will be below issue, which is caused by that the
> > > dma channel will be requested duplicately
> > 
> > Why is this requested a second time? Is this just some missing cleanup
> > on a deferred probe path?
> 
> Not relate with deferred probe.  With DMA1->ASRC->DMA2->ESAI case,
> the DMA1->ASRC->DMA2 is in FE,  ESAI is in BE.  When ESAI drvier
> probe,  DMA3 channel is created with ESAI's "dma:tx" (DMA3 channel
> is not used in this FE-BE case).    When FE-BE startup, DMA2
> channel is created, it needs the ESAI's "dma:tx", so below warning
> comes out.
> 
> > Regards,
> > Lucas
> > 
> > > [  638.906268] sysfs: cannot create duplicate filename '/devices/soc0/soc/2000000.bus/2000000.spba-bus/2024000.esai/dma:tx'
> > > [  638.919061] CPU: 1 PID: 673 Comm: aplay Not tainted 5.7.0-rc1-12956-gfc64b2585593 #287
> > > [  638.927113] Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
> > > [  638.933690] [<c0110dd8>] (unwind_backtrace) from [<c010b8ec>] (show_stack+0x10/0x14)
> > > [  638.941464] [<c010b8ec>] (show_stack) from [<c0557fc0>] (dump_stack+0xe4/0x118)
> > > [  638.948808] [<c0557fc0>] (dump_stack) from [<c032aeb4>] (sysfs_warn_dup+0x50/0x64)
> > > [  638.956406] [<c032aeb4>] (sysfs_warn_dup) from [<c032b1a8>] (sysfs_do_create_link_sd+0xc8/0xd4)
> > > [  638.965134] [<c032b1a8>] (sysfs_do_create_link_sd) from [<c05dc668>] (dma_request_chan+0xb0/0x210)
> > > [  638.974120] [<c05dc668>] (dma_request_chan) from [<c05dc7d0>] (dma_request_slave_channel+0x8/0x14)
> > > [  638.983111] [<c05dc7d0>] (dma_request_slave_channel) from [<c09d5548>] (fsl_asrc_dma_hw_params+0x1e0/0x438)
> > > [  638.992881] [<c09d5548>] (fsl_asrc_dma_hw_params) from [<c09c1654>] (soc_pcm_hw_params+0x4a0/0x6a8)
> > > [  639.001952] [<c09c1654>] (soc_pcm_hw_params) from [<c09c39d4>] (dpcm_fe_dai_hw_params+0x70/0xe4)
> > > [  639.010765] [<c09c39d4>] (dpcm_fe_dai_hw_params) from [<c099b274>] (snd_pcm_hw_params+0x158/0x418)
> > > [  639.019750] [<c099b274>] (snd_pcm_hw_params) from [<c099c5a0>] (snd_pcm_ioctl+0x734/0x183c)
> > > [  639.028129] [<c099c5a0>] (snd_pcm_ioctl) from [<c029ff94>] (ksys_ioctl+0x2ac/0xb98)
> > > [  639.035812] [<c029ff94>] (ksys_ioctl) from [<c0100080>] (ret_fast_syscall+0x0/0x28)
> > > [  639.043490] Exception stack(0xec529fa8 to 0xec529ff0)
> > > [  639.048565] 9fa0:                   bee84650 01321870 00000004 c25c4111 bee84650 0002000f
> > > [  639.056766] 9fc0: bee84650 01321870 01321820 00000036 00001f40 00000000 0002c2f8 00000003
> > > [  639.064964] 9fe0: b6f483fc bee8451c b6ee2655 b6e1dcf8
> > > [  639.070339] fsl-esai-dai 2024000.esai: Cannot create DMA dma:tx symlink
> > > 
> > > Signed-off-by: Shengjiu Wang <shengjiu.wang@nxp.com>
> > > ---
> > >  sound/soc/fsl/imx-pcm-dma.c | 173 +++++++++++++++++++++++++++++++++---
> > >  1 file changed, 159 insertions(+), 14 deletions(-)
> > > 
> > > diff --git a/sound/soc/fsl/imx-pcm-dma.c b/sound/soc/fsl/imx-pcm-dma.c
> > > index 04a9bc749016..dae53b384df4 100644
> > > --- a/sound/soc/fsl/imx-pcm-dma.c
> > > +++ b/sound/soc/fsl/imx-pcm-dma.c
> > > @@ -11,6 +11,7 @@
> > >  #include <linux/dmaengine.h>
> > >  #include <linux/types.h>
> > >  #include <linux/module.h>
> > > +#include <linux/dma-mapping.h>
> > > 
> > >  #include <sound/core.h>
> > >  #include <sound/pcm.h>
> > > @@ -29,24 +30,168 @@ static bool filter(struct dma_chan *chan, void *param)
> > >       return true;
> > >  }
> > > 
> > > -static const struct snd_dmaengine_pcm_config imx_dmaengine_pcm_config = {
> > > -     .prepare_slave_config = snd_dmaengine_pcm_prepare_slave_config,
> > > -     .compat_filter_fn = filter,
> > > -};
> > > +static int imx_pcm_hw_params(struct snd_soc_component *component,
> > > +                          struct snd_pcm_substream *substream,
> > > +                          struct snd_pcm_hw_params *params)
> > > +{
> > > +     struct snd_pcm_runtime *runtime = substream->runtime;
> > > +     struct snd_soc_pcm_runtime *rtd = substream->private_data;
> > > +     struct snd_soc_dai *cpu_dai = asoc_rtd_to_cpu(rtd, 0);
> > > +     struct snd_dmaengine_dai_dma_data *dma_data;
> > > +     struct dma_slave_config config;
> > > +     struct dma_chan *chan;
> > > +     int ret = 0;
> > > 
> > > -int imx_pcm_dma_init(struct platform_device *pdev, size_t size)
> > > +     snd_pcm_set_runtime_buffer(substream, &substream->dma_buffer);
> > > +     runtime->dma_bytes = params_buffer_bytes(params);
> > > +
> > > +     chan = snd_dmaengine_pcm_get_chan(substream);
> > > +     if (!chan)
> > > +             return -EINVAL;
> > > +
> > > +     ret = snd_hwparams_to_dma_slave_config(substream, params, &config);
> > > +     if (ret)
> > > +             return ret;
> > > +
> > > +     dma_data = snd_soc_dai_get_dma_data(cpu_dai, substream);
> > > +     if (!dma_data)
> > > +             return -EINVAL;
> > > +
> > > +     snd_dmaengine_pcm_set_config_from_dai_data(substream,
> > > +                                                dma_data,
> > > +                                                &config);
> > > +     return dmaengine_slave_config(chan, &config);
> > > +}
> > > +
> > > +static int imx_pcm_hw_free(struct snd_soc_component *component,
> > > +                        struct snd_pcm_substream *substream)
> > >  {
> > > -     struct snd_dmaengine_pcm_config *config;
> > > +     snd_pcm_set_runtime_buffer(substream, NULL);
> > > +     return 0;
> > > +}
> > > +
> > > +static snd_pcm_uframes_t imx_pcm_pointer(struct snd_soc_component *component,
> > > +                                      struct snd_pcm_substream *substream)
> > > +{
> > > +     return snd_dmaengine_pcm_pointer(substream);
> > > +}
> > > +
> > > +static int imx_pcm_trigger(struct snd_soc_component *component,
> > > +                        struct snd_pcm_substream *substream, int cmd)
> > > +{
> > > +     return snd_dmaengine_pcm_trigger(substream, cmd);
> > > +}
> > > +
> > > +static int imx_pcm_open(struct snd_soc_component *component,
> > > +                     struct snd_pcm_substream *substream)
> > > +{
> > > +     struct snd_soc_pcm_runtime *rtd = substream->private_data;
> > > +     bool tx = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
> > > +     struct snd_soc_dai *cpu_dai = asoc_rtd_to_cpu(rtd, 0);
> > > +     struct snd_dmaengine_dai_dma_data *dma_data;
> > > +     struct device *dev = component->dev;
> > > +     struct snd_pcm_hardware hw;
> > > +     struct dma_chan *chan;
> > > +     int ret;
> > > +
> > > +     ret = snd_pcm_hw_constraint_integer(substream->runtime,
> > > +                                         SNDRV_PCM_HW_PARAM_PERIODS);
> > > +     if (ret < 0) {
> > > +             dev_err(dev, "failed to set pcm hw params periods\n");
> > > +             return ret;
> > > +     }
> > > +
> > > +     dma_data = snd_soc_dai_get_dma_data(cpu_dai, substream);
> > > +     if (!dma_data)
> > > +             return -EINVAL;
> > > +
> > > +     chan = dma_request_slave_channel(cpu_dai->dev, tx ? "tx" : "rx");
> > > +     if (!chan) {
> > > +             /* Try to request channel using compat_filter_fn */
> > > +             chan = snd_dmaengine_pcm_request_channel(filter,
> > > +                                                      dma_data->filter_data);
> > > +             if (!chan)
> > > +                     return -ENXIO;
> > > +     }
> > > 
> > > -     config = devm_kzalloc(&pdev->dev,
> > > -                     sizeof(struct snd_dmaengine_pcm_config), GFP_KERNEL);
> > > -     if (!config)
> > > -             return -ENOMEM;
> > > -     *config = imx_dmaengine_pcm_config;
> > > +     ret = snd_dmaengine_pcm_open(substream, chan);
> > > +     if (ret)
> > > +             goto pcm_open_fail;
> > > 
> > > -     return devm_snd_dmaengine_pcm_register(&pdev->dev,
> > > -             config,
> > > -             SND_DMAENGINE_PCM_FLAG_COMPAT);
> > > +     memset(&hw, 0, sizeof(hw));
> > > +     hw.info = SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID |
> > > +                     SNDRV_PCM_INFO_INTERLEAVED;
> > > +     hw.periods_min = 2;
> > > +     hw.periods_max = UINT_MAX;
> > > +     hw.period_bytes_min = 256;
> > > +     hw.period_bytes_max = dma_get_max_seg_size(chan->device->dev);
> > > +     hw.buffer_bytes_max = IMX_DEFAULT_DMABUF_SIZE;
> > > +     hw.fifo_size = dma_data->fifo_size;
> > > +
> > > +     /* Refine the hw according to caps of DMA. */
> > > +     ret = snd_dmaengine_pcm_refine_runtime_hwparams(substream,
> > > +                                                     dma_data,
> > > +                                                     &hw,
> > > +                                                     chan);
> > > +     if (ret < 0)
> > > +             goto refine_runtime_hwparams_fail;
> > > +
> > > +     snd_soc_set_runtime_hwparams(substream, &hw);
> > > +
> > > +     /* Support allocate memory from IRAM */
> > > +     ret = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_IRAM,
> > > +                               chan->device->dev,
> > > +                               hw.buffer_bytes_max,
> > > +                               &substream->dma_buffer);
> > > +     if (ret < 0)
> > > +             goto alloc_pagas_fail;
> > > +
> > > +     return 0;
> > > +
> > > +alloc_pagas_fail:
> > > +refine_runtime_hwparams_fail:
> > > +     snd_dmaengine_pcm_close(substream);
> > > +pcm_open_fail:
> > > +     dma_release_channel(chan);
> > > +
> > > +     return ret;
> > > +}
> > > +
> > > +static int imx_pcm_close(struct snd_soc_component *component,
> > > +                      struct snd_pcm_substream *substream)
> > > +{
> > > +     if (substream) {
> > > +             snd_dma_free_pages(&substream->dma_buffer);
> > > +             substream->dma_buffer.area = NULL;
> > > +             substream->dma_buffer.addr = 0;
> > > +     }
> > > +
> > > +     return snd_dmaengine_pcm_close_release_chan(substream);
> > > +}
> > > +
> > > +static int imx_pcm_new(struct snd_soc_component *component,
> > > +                    struct snd_soc_pcm_runtime *rtd)
> > > +{
> > > +     struct snd_card *card = rtd->card->snd_card;
> > > +
> > > +     return dma_coerce_mask_and_coherent(card->dev, DMA_BIT_MASK(32));
> > > +}
> > > +
> > > +static const struct snd_soc_component_driver imx_pcm_component = {
> > > +     .name           = "imx-pcm-dma",
> > > +     .pcm_construct  = imx_pcm_new,
> > > +     .open           = imx_pcm_open,
> > > +     .close          = imx_pcm_close,
> > > +     .hw_params      = imx_pcm_hw_params,
> > > +     .hw_free        = imx_pcm_hw_free,
> > > +     .trigger        = imx_pcm_trigger,
> > > +     .pointer        = imx_pcm_pointer,
> > > +};
> > > +
> > > +int imx_pcm_dma_init(struct platform_device *pdev, size_t size)
> > > +{
> > > +     return devm_snd_soc_register_component(&pdev->dev,
> > > +                                            &imx_pcm_component, NULL, 0);
> > >  }
> > >  EXPORT_SYMBOL_GPL(imx_pcm_dma_init);
> > >