On 2018-12-21 17:44, Chen-Yu Tsai wrote:

On Fri, Dec 21, 2018 at 11:21 PM [off-list ref] wrote:

quoted

From: Marcus Cooper <redacted>

Bypass the regmap cache when flushing the i2s FIFOs and modify the tables
to reflect this.

Signed-off-by: Marcus Cooper <redacted>
---
 sound/soc/sunxi/sun4i-i2s.c | 29 +++++++++--------------------
 1 file changed, 9 insertions(+), 20 deletions(-)

diff --git a/sound/soc/sunxi/sun4i-i2s.c b/sound/soc/sunxi/sun4i-i2s.c
index d5ec1a20499d..64d073cb2aee 100644
--- a/sound/soc/sunxi/sun4i-i2s.c
+++ b/sound/soc/sunxi/sun4i-i2s.c

@@ -548,9 +548,11 @@ static int sun4i_i2s_set_fmt(struct snd_soc_dai *dai, unsigned int fmt)
 static void sun4i_i2s_start_capture(struct sun4i_i2s *i2s)
 {
        /* Flush RX FIFO */
+       regcache_cache_bypass(i2s->regmap, true);
        regmap_update_bits(i2s->regmap, SUN4I_I2S_FIFO_CTRL_REG,
                           SUN4I_I2S_FIFO_CTRL_FLUSH_RX,
                           SUN4I_I2S_FIFO_CTRL_FLUSH_RX);
+       regcache_cache_bypass(i2s->regmap, false);

IIRC the flush cache bit is self-clearing. So you likely want to mark
this register as volatile. If it is marked as volatile, then all access
to that register bypasses the cache, so the regcache_cache_bypass calls
are unneeded.

I helped test this together with Marcus and when I tested with this
register marked
as volatile audio started to stutter, still unclear why audio starts to
stutter.

Without this cache bypass the flush TX/RX bits gets cached and flush
happens unexpectedly
resulting in multi channel audio getting mapped to wrong speaker.
Other ASoC codecs and fsl_spdif.c seems to use similar cache bypass for
reset/flush.

However, looking at the code, the write would seem to be ignored if the
regmap is in the cache_only state. We only set this when the bus clock
is disabled. Under such a condition, bypassing the cache and forcing a
write would be unwise, as the system either drops the write, or stalls
altogether.

quoted

        /* Clear RX counter */
        regmap_write(i2s->regmap, SUN4I_I2S_RX_CNT_REG, 0);

@@ -569,9 +571,11 @@ static void sun4i_i2s_start_capture(struct sun4i_i2s *i2s)
 static void sun4i_i2s_start_playback(struct sun4i_i2s *i2s)
 {
        /* Flush TX FIFO */
+       regcache_cache_bypass(i2s->regmap, true);
        regmap_update_bits(i2s->regmap, SUN4I_I2S_FIFO_CTRL_REG,
                           SUN4I_I2S_FIFO_CTRL_FLUSH_TX,
                           SUN4I_I2S_FIFO_CTRL_FLUSH_TX);
+       regcache_cache_bypass(i2s->regmap, false);

        /* Clear TX counter */
        regmap_write(i2s->regmap, SUN4I_I2S_TX_CNT_REG, 0);

@@ -703,13 +707,7 @@ static const struct snd_soc_component_driver sun4i_i2s_component = {

 static bool sun4i_i2s_rd_reg(struct device *dev, unsigned int reg)
 {
-       switch (reg) {
-       case SUN4I_I2S_FIFO_TX_REG:
-               return false;
-
-       default:
-               return true;
-       }
+       return true;

I don't understand why this is relevant. Do you need to read back from the TX
FIFO?

This change was inspired by c66234cfedfc "ASoC: rockchip: i2s: fix
playback after runtime resume" [1]
On resume a cached sample would be written to FIFO_TX_REG unless it is
marked volatile,
the rockchip commit indicated that read is needed for volatile regs.

[1]
https://github.com/torvalds/linux/commit/c66234cfedfc3e6e3b62563a5f2c1562be09a35d

If so, just drop the call-back altogether. If no callback is provided and no
rd_table is provided either, it defaults to all registers under max_register
(if max_register < 0) are readable.

However this seems like it deserves to be a separate patch (where you explain
in the commit log why it's needed).

Regards
ChenYu

quoted

 }

 static bool sun4i_i2s_wr_reg(struct device *dev, unsigned int reg)

@@ -728,6 +726,8 @@ static bool sun4i_i2s_volatile_reg(struct device *dev, unsigned int reg)
 {
        switch (reg) {
        case SUN4I_I2S_FIFO_RX_REG:
+       case SUN4I_I2S_FIFO_TX_REG:
+       case SUN4I_I2S_FIFO_STA_REG:
        case SUN4I_I2S_INT_STA_REG:
        case SUN4I_I2S_RX_CNT_REG:
        case SUN4I_I2S_TX_CNT_REG:

@@ -738,23 +738,12 @@ static bool sun4i_i2s_volatile_reg(struct device *dev, unsigned int reg)
        }
 }

-static bool sun8i_i2s_rd_reg(struct device *dev, unsigned int reg)
-{
-       switch (reg) {
-       case SUN8I_I2S_FIFO_TX_REG:
-               return false;
-
-       default:
-               return true;
-       }
-}
-
 static bool sun8i_i2s_volatile_reg(struct device *dev, unsigned int reg)
 {
        if (reg == SUN8I_I2S_INT_STA_REG)
                return true;
        if (reg == SUN8I_I2S_FIFO_TX_REG)
-               return false;
+               return true;

        return sun4i_i2s_volatile_reg(dev, reg);
 }

@@ -809,7 +798,7 @@ static const struct regmap_config sun8i_i2s_regmap_config = {
        .reg_defaults   = sun8i_i2s_reg_defaults,
        .num_reg_defaults       = ARRAY_SIZE(sun8i_i2s_reg_defaults),
        .writeable_reg  = sun4i_i2s_wr_reg,
-       .readable_reg   = sun8i_i2s_rd_reg,
+       .readable_reg   = sun4i_i2s_rd_reg,
        .volatile_reg   = sun8i_i2s_volatile_reg,
 };

--

2.20.1

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