[alsa-devel] [RESEND PATCH v2 1/1] ASoC: dwc: fix dma stop transferring issue
Designware I2S uses tx empty and rx available signals as the DMA handshaking signals. during music playing, if XRUN occurs, i2s_stop() function will be executed and both tx and rx irq are masked, when music continues to be played, i2s_start() is executed but both tx and rx irq are not unmasked which cause I2S stop sending DMA handshaking signal to DMA controller, and it finally causes music playing will be stopped once XRUN occurs for the first time.
Signed-off-by: Yitian Bu yitian.bu@tangramtek.com --- changes in V2: - add definition for i and irq --- sound/soc/dwc/designware_i2s.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/sound/soc/dwc/designware_i2s.c b/sound/soc/dwc/designware_i2s.c index a3e97b4..76b2e19 100644 --- a/sound/soc/dwc/designware_i2s.c +++ b/sound/soc/dwc/designware_i2s.c @@ -141,13 +141,22 @@ static inline void i2s_clear_irqs(struct dw_i2s_dev *dev, u32 stream) static void i2s_start(struct dw_i2s_dev *dev, struct snd_pcm_substream *substream) { - + u32 i, irq; i2s_write_reg(dev->i2s_base, IER, 1);
- if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) + if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) { + for (i = 0; i < 4; i++) { + irq = i2s_read_reg(dev->i2s_base, IMR(i)); + i2s_write_reg(dev->i2s_base, IMR(i), irq & ~0x30); + } i2s_write_reg(dev->i2s_base, ITER, 1); - else + } else { + for (i = 0; i < 4; i++) { + irq = i2s_read_reg(dev->i2s_base, IMR(i)); + i2s_write_reg(dev->i2s_base, IMR(i), irq & ~0x03); + } i2s_write_reg(dev->i2s_base, IRER, 1); + }
i2s_write_reg(dev->i2s_base, CER, 1); }
On Tue, Sep 29, 2015 at 10:43:17PM +0800, yitian wrote:
Designware I2S uses tx empty and rx available signals as the DMA handshaking signals. during music playing, if XRUN occurs, i2s_stop() function will be executed and both tx and rx irq are masked, when music continues to be played, i2s_start() is executed but both tx and rx irq are not unmasked which cause I2S stop sending DMA handshaking signal to DMA controller, and it finally causes music playing will be stopped once XRUN occurs for the first time.
I'm a bit concerned about how this code ever worked given the above description - is there some race condition which allows things to work if we're lucky?
From: linux-arm-kernel [mailto:linux-arm-kernel-bounces@lists.infradead.org] On Behalf Of Mark Brown Sent: Thursday, October 1, 2015 2:22 AM To: yitian yitian.bu@tangramtek.com Cc: alsa-devel@alsa-project.org; wsa@the-dreams.de; linux-kernel@vger.kernel.org; Andrew.Jackson@arm.com; tiwai@suse.com; lgirdwood@gmail.com; perex@perex.cz; linux-arm-kernel@lists.infradead.org Subject: Re: [RESEND PATCH v2 1/1] ASoC: dwc: fix dma stop transferring issue
On Tue, Sep 29, 2015 at 10:43:17PM +0800, yitian wrote:
Designware I2S uses tx empty and rx available signals as the DMA handshaking signals. during music playing, if XRUN occurs, i2s_stop() function will be executed and both tx and rx irq are masked, when music continues to be played, i2s_start() is executed but both tx and rx irq are not unmasked which cause I2S stop sending DMA handshaking signal to DMA controller, and it finally causes music playing will be stopped once XRUN occurs for the first time.
I'm a bit concerned about how this code ever worked given the above description - is there some race condition which allows things to work if we're lucky?
Hi Mark:
Thanks for your comments. I think maybe two reasons: 1. designware I2S IP in my chipset(new design) is using tx empty and rx available signal as the DMA handshaking signal, but it may be not true for all chipsets. If I2S has separate signal as DMA handshaking signal, mask irq should not impact DMA transfer. But Synopsys's engineer recommend us to use tx and rx irq signal as the DMA handshaking signal, meanwhile we cannot find separate DMA handshaking signal from designware's IP spec, that's why tx/rx irq will impact DMA transfer.
2. I am using a FPGA for test, the cpu frequency of it is only 26MHz, that means XRUN is very easy to happen on my board. But I guess most of the developers are using real chipset which can have at least 600MHz frequency so XRUN is not easy to be reproduced. As my test, No XUN, no this bug...
Hi Mark:
From: alsa-devel-bounces@alsa-project.org [mailto:alsa-devel-bounces@alsa-project.org] On Behalf Of yitian Sent: Thursday, October 1, 2015 10:25 AM To: 'Mark Brown' broonie@kernel.org Cc: alsa-devel@alsa-project.org; wsa@the-dreams.de; linux-kernel@vger.kernel.org; Andrew.Jackson@arm.com; lgirdwood@gmail.com; tiwai@suse.com; linux-arm-kernel@lists.infradead.org Subject: Re: [alsa-devel] [RESEND PATCH v2 1/1] ASoC: dwc: fix dma stop transferring issue
From: linux-arm-kernel [mailto:linux-arm-kernel-bounces@lists.infradead.org] On Behalf Of
Mark
Brown Sent: Thursday, October 1, 2015 2:22 AM To: yitian yitian.bu@tangramtek.com Cc: alsa-devel@alsa-project.org; wsa@the-dreams.de; linux-kernel@vger.kernel.org; Andrew.Jackson@arm.com;
tiwai@suse.com;
lgirdwood@gmail.com; perex@perex.cz; linux-arm-kernel@lists.infradead.org Subject: Re: [RESEND PATCH v2 1/1] ASoC: dwc: fix dma stop transferring issue
On Tue, Sep 29, 2015 at 10:43:17PM +0800, yitian wrote:
Designware I2S uses tx empty and rx available signals as the DMA handshaking signals. during music playing, if XRUN occurs, i2s_stop() function will be executed and both tx and rx irq are masked, when music continues to be played, i2s_start() is executed but both tx and rx irq are not unmasked which cause I2S stop sending DMA handshaking signal to DMA controller, and it finally causes music playing will be stopped once XRUN occurs for the first time.
I'm a bit concerned about how this code ever worked given the above description - is there some race condition which allows things to work if we're lucky?
Hi Mark:
Thanks for your comments. I think maybe two reasons:
- designware I2S IP in my chipset(new design) is using tx empty and rx
available signal as the DMA handshaking signal, but it may be not true for all chipsets. If I2S has separate signal as DMA handshaking signal,
mask
irq should not impact DMA transfer. But Synopsys's engineer recommend us to use tx and rx irq signal as the DMA handshaking signal, meanwhile we cannot find separate DMA handshaking signal from designware's IP spec, that's why tx/rx irq will impact DMA transfer.
- I am using a FPGA for test, the cpu frequency of it is only 26MHz, that
means XRUN is very easy to happen on my board. But I guess most of the developers are using real chipset which can have at least 600MHz frequency so XRUN is not easy to be reproduced. As my test, No XUN, no this bug...
Do I need to provide anything else for this patch? Thanks.
On Thu, Oct 01, 2015 at 10:24:42AM +0800, yitian wrote:
I think maybe two reasons:
- designware I2S IP in my chipset(new design) is using tx empty and rx
available signal as the DMA handshaking signal, but it may be not true for all chipsets. If I2S has separate signal as DMA handshaking signal, mask irq should not impact DMA transfer. But Synopsys's engineer recommend us to use tx and rx irq signal as the DMA handshaking signal, meanwhile we cannot find separate DMA handshaking signal from designware's IP spec, that's why tx/rx irq will impact DMA transfer.
If that's what the Synopsis engineers recommend I'd guess that other integrations are doing the same thing.
- I am using a FPGA for test, the cpu frequency of it is only 26MHz, that
means XRUN is very easy to happen on my board. But I guess most of the developers are using real chipset which can have at least 600MHz frequency so XRUN is not easy to be reproduced. As my test, No XUN, no this bug...
Ah, that might be it - it might just be that other systems are working due to race conditions.
On Tue, Sep 29, 2015 at 10:43:17PM +0800, yitian wrote:
--- a/sound/soc/dwc/designware_i2s.c +++ b/sound/soc/dwc/designware_i2s.c @@ -141,13 +141,22 @@ static inline void i2s_clear_irqs(struct dw_i2s_dev *dev, u32 stream)
This doesn't apply because it's been corrupted by line wrapping - git am can't understand it. Since it's just that one line I fixed it up by hand but please look at your mail setup to make sure this works (this might've been what happened with your other patch yesterday).
Hi Mark:
This doesn't apply because it's been corrupted by line wrapping - git am can't understand it. Since it's just that one line I fixed it up by hand but please look at your mail setup to make sure this works (this might've been what happened with your other patch yesterday).
After you said it corrupted git am, I used git send-email to send the "correct irq clear method" patch and hopefully that was correct. I will be careful next time, thanks a lot for your patient help.
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yitian