There is a hardware issue when using capture and playback at the same time. In the tested scenario, the capture stream was started slightly before the playback stream. The first time the application starts after a powerup, there is a high probability that the SSI unit does not send a request to the SDMA unit. The playback does not work. I tested this on i.MX53 with SSI unit 2 kernel 3.10.10.
Here is a register dump of the situation: SDMA 0x63fb0000 00000000: c0040000 00000000 0000001e 00000000 00000010: 00000001 ffffffff 00000000 e03efa41 00000020: 00000000 00000000 00000000 00000000 00000030: 00000064 00000000 00000003 00000000 00000040: 00000000 00000000 00000000 00006000 00000050: 00000000 00000000 00000001 00004050 00000060: 01208000 00000000 00000000 00000000 /* 0x60: EVT_MIRROR showing all received DMA requests */ ^ This should be a 3 instead. Bits 24 and 25 are the DMA requests for RX and TX. Bit 25 is not set, DMA request 25 is missing.
SSI 0x50014000 00000000: 00000000 00000000 0000005f 00000000 00000010: 00000457 000050c1 01f80f00 0000028d /* 0x14: ISR Interrupt status register */ ^ At 0x14 we can clearly see the last bit is set (0x1) which is TFE0, Transmit FIFO 0 empty. So it should automatically request data from the DMA engine, but it doesn't.
00000020: 0000028d 0004e000 00040000 000010dd 00000030: 00001f1f 00000000 00000000 00000000 00000040: 00000000 00000000 00000000 00000000 00000050: 00000000 00000000 ........ STATS (/sys/bus/platform/devices/50014000.ssi/statistics) rfrc=0 tfrc=0 roe1=0 roe0=0 tue1=0 tue0=1094475
I could solve this issue by filling the transmit FIFO with data. After that, the SDMA unit receives DMA request 25 again and audio playback works.
This patch adds TUE0 interrupt handler which fills FIFO0 with arbitrary data.
Signed-off-by: Markus Pargmann mpa@pengutronix.de ---
Hi,
does anyone have an idea why the SSI unit does not request DMA by its own at the beginning? Or is it a hardware errata that is not listed yet?
Regards,
Markus Pargmann
sound/soc/fsl/fsl_ssi.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c index 6b81d0c..8faf2b5 100644 --- a/sound/soc/fsl/fsl_ssi.c +++ b/sound/soc/fsl/fsl_ssi.c @@ -269,9 +269,14 @@ static irqreturn_t fsl_ssi_isr(int irq, void *dev_id) }
if (sisr & CCSR_SSI_SISR_TUE0) { + int i; + ssi_private->stats.tue0++; sisr2 |= CCSR_SSI_SISR_TUE0; ret = IRQ_HANDLED; + + for (i = 0; i != ssi_private->fifo_depth; ++i) + write_ssi(0x0, &ssi->stx0); }
if (sisr & CCSR_SSI_SISR_TFS) {