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ssp: refine the RX FIFO flushing logic 

The SSSR_BSY is not necessary for flushing, we need to read out entries
every time the FIFO is not empty. This flushing may need take place
several rounds, and we need to wait 1 sample time between 2 flushing
rounds.

Fixes #3525

Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
This commit is contained in:
Keyon Jie 2020-10-22 14:24:31 +08:00 committed by Liam Girdwood
parent 322839449d
commit 60dfaa7ee3
2 changed files with 23 additions and 15 deletions
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34
src/drivers/intel/ssp/ssp.c
View File

@ -67,24 +67,32 @@ static void ssp_empty_tx_fifo(struct dai *dai)
/* empty SSP receive FIFO */
static void ssp_empty_rx_fifo(struct dai *dai)
{
struct timer *timer = timer_get();
uint64_t deadline = platform_timer_get(timer) +
clock_ms_to_ticks(PLATFORM_DEFAULT_CLOCK, 1) *
SSP_RX_FLUSH_TIMEOUT / 1000;
struct ssp_pdata *ssp = dai_get_drvdata(dai);
uint64_t sample_ticks = clock_ticks_per_sample(PLATFORM_DEFAULT_CLOCK,
ssp->params.fsync_rate);
uint32_t retry = SSP_RX_FLUSH_RETRY_MAX;
uint32_t entries;
uint32_t i;
/*
* To make sure all the RX FIFO entries are read out for the flushing,
* we need to wait until the SSSR_RNE is cleared after the SSP link is
* stopped (the SSSR_BSY is cleared), otherwise, there might be
* obsoleted entries remained in the FIFO, which will impact the next
* run with the SSP RX and lead to samples mismatched issue.
* we need to wait a minimal SSP port delay after entries are all read,
* and then re-check to see if there is any subsequent entries written
* to the FIFO. This will help to make sure there is no sample mismatched
* issue for the next run with the SSP RX.
*/
do {
while (ssp_read(dai, SSSR) & SSSR_RNE)
/* read to empty the fifo */
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++)
/* read to try empty fifo */
ssp_read(dai, SSDR);
} while ((ssp_read(dai, SSSR) & SSSR_BSY) &&
platform_timer_get(timer) < deadline);
/* wait to get valid fifo status and re-check */
wait_delay(sample_ticks);
entries = SSCR3_RFL_VAL(ssp_read(dai, SSCR3));
dai_dbg(dai, "ssp_empty_rx_fifo(), after flushing, entries %d", entries);
}
/* clear interrupt */
ssp_update_bits(dai, SSSR, SSSR_ROR, SSSR_ROR);

4
src/include/sof/drivers/ssp.h
View File

@ -220,8 +220,8 @@ extern const struct dai_driver ssp_driver;
/* For 8000 Hz rate one sample is transmitted within 125us */
#define SSP_MAX_SEND_TIME_PER_SAMPLE 125
/* SSP flush timeout in microseconds */
#define SSP_RX_FLUSH_TIMEOUT 200
/* SSP flush retry counts maximum */
#define SSP_RX_FLUSH_RETRY_MAX 16
#define ssp_irq(ssp) \
ssp->plat_data.irq