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intel: ssp: SSP rx start fixes #7564

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kv2019i wants to merge 2 commits into from
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intel: ssp: SSP rx start fixes #7564

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intel: ssp: do not read data directly if DMA is active
kv2019i May 5, 2023
1bb0947
intel: ssp: drain RX fifo when starting
kv2019i May 5, 2023
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17 changes: 16 additions & 1 deletion src/drivers/intel/ssp/ssp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -74,9 +74,18 @@ static void ssp_empty_rx_fifo(struct dai *dai)
uint64_t sample_ticks = clock_ticks_per_sample(PLATFORM_DEFAULT_CLOCK,
ssp->params.fsync_rate);
uint32_t retry = SSP_RX_FLUSH_RETRY_MAX;
bool read_ssdr = ssp->state[DAI_DIR_CAPTURE] <= COMP_STATE_PREPARE;
uint32_t entries;
uint32_t i;

#if CONFIG_DMA_SUSPEND_DRAIN
/*
* in drain mode, DMA is stopped before DAI,
* so flush must be done with direct register read
*/
read_ssdr = true;
#endif

/*
* To make sure all the RX FIFO entries are read out for the flushing,
* we need to wait a minimal SSP port delay after entries are all read,
Expand All @@ -87,7 +96,8 @@ static void ssp_empty_rx_fifo(struct dai *dai)
while ((ssp_read(dai, SSSR) & SSSR_RNE) && retry--) {
entries = SSCR3_RFL_VAL(ssp_read(dai, SSCR3));
dai_dbg(dai, "ssp_empty_rx_fifo(), before flushing, entries %d", entries);
for (i = 0; i < entries + 1; i++)

for (i = 0; read_ssdr && i < entries + 1; i++)
/* read to try empty fifo */
ssp_read(dai, SSDR);
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@ujfalusi ujfalusi May 8, 2023

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for readability I would be more explicit:

if (read_ssdr) {
	/* read to try empty fifo */
	for (i = 0; i < entries + 1; i++)
		ssp_read(dai, SSDR);
}

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@plbossart plbossart May 8, 2023

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it's not just readability, there's no reason to test read_ssdr at every loop - though the compiler might be smart enough to move this up?

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@kv2019i kv2019i May 9, 2023

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Fixed in the mainline version #7577 -- will resubmit to stable-2.2 once merged.


Expand Down Expand Up @@ -963,6 +973,11 @@ static void ssp_early_start(struct dai *dai, int direction)

key = k_spin_lock(&dai->lock);

if (direction == DAI_DIR_CAPTURE) {
/* RX fifo must be cleared before start */
ssp_empty_rx_fifo(dai);
}

/* request mclk/bclk */
ssp_pre_start(dai);

Expand Down