From 61fcf10a0ee44763e0347b297a377137f8950772 Mon Sep 17 00:00:00 2001 From: Arnaud Mouiche Date: Tue, 3 May 2016 14:13:59 +0200 Subject: [PATCH] ASoC: fsl_ssi: Fix channel slipping in Playback at startup Previously, SCR.SSIEN and SCR.TE were enabled at once if no capture stream was also running. This may not give a chance for the DMA to write the first sample in TX FIFO before the streaming starts on the PCM bus, inserting void samples first. Those void samples are then responsible for slipping the channels. Signed-off-by: Arnaud Mouiche Reviewed-by: Fabio Estevam Tested-by: Caleb Crome Signed-off-by: Mark Brown --- sound/soc/fsl/fsl_ssi.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-) diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c index 47ebb835f3f5..8944af542b4f 100644 --- a/sound/soc/fsl/fsl_ssi.c +++ b/sound/soc/fsl/fsl_ssi.c @@ -507,8 +507,40 @@ static void fsl_ssi_config(struct fsl_ssi_private *ssi_private, bool enable, config_done: /* Enabling of subunits is done after configuration */ - if (enable) + if (enable) { + if (ssi_private->use_dma && (vals->scr & CCSR_SSI_SCR_TE)) { + /* + * Be sure the Tx FIFO is filled when TE is set. + * Otherwise, there are some chances to start the + * playback with some void samples inserted first, + * generating a channel slip. + * + * First, SSIEN must be set, to let the FIFO be filled. + * + * Notes: + * - Limit this fix to the DMA case until FIQ cases can + * be tested. + * - Limit the length of the busy loop to not lock the + * system too long, even if 1-2 loops are sufficient + * in general. + */ + int i; + int max_loop = 100; + regmap_update_bits(regs, CCSR_SSI_SCR, + CCSR_SSI_SCR_SSIEN, CCSR_SSI_SCR_SSIEN); + for (i = 0; i < max_loop; i++) { + u32 sfcsr; + regmap_read(regs, CCSR_SSI_SFCSR, &sfcsr); + if (CCSR_SSI_SFCSR_TFCNT0(sfcsr)) + break; + } + if (i == max_loop) { + dev_err(ssi_private->dev, + "Timeout waiting TX FIFO filling\n"); + } + } regmap_update_bits(regs, CCSR_SSI_SCR, vals->scr, vals->scr); + } } -- GitLab