On Fri, Oct 30, 2015 at 03:04:37PM -0700, Caleb Crome wrote:
** Problem 1 *******
When I enable your patch in single fifo mode we get maxburst lost samples at the beginning of the stream. The important bit is below. It doesn't matter if the SSIEN comes before or after the TDMAE, the samples are lost. Surely because something in the fsl_ssi_config clears the fifo. I didn't look into that yet.
The config function has gone way complicated than I realized. But you may need to dig a little bit to make a perfect point to insert your change as it might break other platforms: AC97 and old i.MX and MPC.
--------------------------- snip -------------------
If instead, I do the SSIEN at the bottom of the fsl_ssi_configure function like this, it works perfectly (in single fifo mode)
--------------------------- snip ------------------- +++ b/sound/soc/fsl/fsl_ssi.c @@ -435,8 +435,49 @@ 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) {
/* eanble SSI */regmap_update_bits(regs, CCSR_SSI_SCR,CCSR_SSI_SCR_SSIEN,CCSR_SSI_SCR_SSIEN);/** We must wait here until the DMA actually manages to* get a word into the Tx FIFO. Only if starting a Tx* stream.* In tests on an MX6 at 1GHz clock speed, the do* loop below never iterated at all (i.e. it dropped* through without repeating ever. which means that* the DMA has had time to get some words into the TX* buffer. In fact, the tfcnt0 was always 13, so it* was quite full by the time it reached this point,* so this do loop should never be a bottleneck. If* max iterations is hit, then something might be* wrong. report it in that case.*/int tfcnt0 = 0;int tfcnt1 = 1;int max_iterations = 1000;if (vals->scr & CCSR_SSI_SCR_TE) {u32 sfcsr;do {regmap_read(regs, CCSR_SSI_SFCSR, &sfcsr);tfcnt0 = CCSR_SSI_SFCSR_TFCNT0(sfcsr);tfcnt1 = CCSR_SSI_SFCSR_TFCNT0(sfcsr);} while(max_iterations-- && (tfcnt0 == 0) && (tfcnt1 == 0));}if (max_iterations <= 0) {/** The DMA definitely should have stuck at* least a word into the FIFO by now. Report* an error, but continue on blindly anyway,* even though the SSI might not start right.*/struct platform_device *pdev = ssi_private->pdev;dev_err(&pdev->dev, "max_iterations reached when""starting SSI Tx\n");}
Looks like polling is the only way to safely kick off. It's okay. But I would like to see how the change will be after merging the simultaneous TE/RE work around. It may need go a long way with other platform users.