[v2,04/16] ASoC: fsl_ssi: Rename fsl_ssi_disable_val macro

Commit Message

Nicolin Chen Jan. 11, 2018, 6:43 a.m. UTC

The define of fsl_ssi_disable_val is not so clear as it mixes two
steps of calculations together. And those parameter names are also
a bit long to read.

Since it just tries to exclude the shared bits from the regvals of
current stream while the opposite stream is active, it's better to
use something like ssi_excl_shared_bits.

This patch also bisects fsl_ssi_disable_val into two macros of two
corresponding steps and then shortens its parameter names. It also
updates callers in the fsl_ssi_config() accordingly.

Signed-off-by: Nicolin Chen <[e-mail]>
Tested-by: Caleb Crome <[e-mail]>
---
 sound/soc/fsl/fsl_ssi.c | 54 ++++++++++++++++++++-----------------------------
 1 file changed, 22 insertions(+), 32 deletions(-)

Comments

Maciej S. Szmigiero Jan. 14, 2018, 10:34 p.m. UTC | #1

On 11.01.2018 07:43, Nicolin Chen wrote:
> The define of fsl_ssi_disable_val is not so clear as it mixes two
> steps of calculations together. And those parameter names are also
> a bit long to read.
> 
> Since it just tries to exclude the shared bits from the regvals of
> current stream while the opposite stream is active, it's better to
> use something like ssi_excl_shared_bits.
> 
> This patch also bisects fsl_ssi_disable_val into two macros of two
> corresponding steps and then shortens its parameter names. It also
> updates callers in the fsl_ssi_config() accordingly.
> 
> Signed-off-by: Nicolin Chen <[e-mail]>
> Tested-by: Caleb Crome <[e-mail]>
> ---
>  sound/soc/fsl/fsl_ssi.c | 54 ++++++++++++++++++++-----------------------------
>  1 file changed, 22 insertions(+), 32 deletions(-)
> 
> diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
> index aa14a5d..f026386 100644
> --- a/sound/soc/fsl/fsl_ssi.c
> +++ b/sound/soc/fsl/fsl_ssi.c
> @@ -445,16 +445,10 @@ static void fsl_ssi_config(struct fsl_ssi *ssi, bool enable,
>  	bool dir = (&ssi->regvals[TX] == vals) ? TX : RX;
>  	struct regmap *regs = ssi->regs;
>  	struct fsl_ssi_regvals *avals;
> -	int nr_active_streams;
> -	int keep_active;
> -
> -	nr_active_streams = !!(ssi->streams & BIT(TX)) +
> -			    !!(ssi->streams & BIT(RX));
> +	bool aactive;
>  
> -	if (nr_active_streams - 1 > 0)
> -		keep_active = 1;
> -	else
> -		keep_active = 0;
> +	/* Check if the opposite stream is active */
> +	aactive = ssi->streams & BIT(!dir);
				     ^
Here an implicit assumption that either RX == 0, TX == 1 or
RX == 1, TX == 0 still remains.

Maciej

Nicolin Chen Jan. 15, 2018, 12:03 a.m. UTC | #2

On Sun, Jan 14, 2018 at 11:34:37PM +0100, Maciej S. Szmigiero wrote:

> > +	/* Check if the opposite stream is active */
> > +	aactive = ssi->streams & BIT(!dir);
> 				     ^
> Here an implicit assumption that either RX == 0, TX == 1 or
> RX == 1, TX == 0 still remains.

I would try to get rid of this !dir. However the regvals is
defined as regvals[2] so this assumption (either RX == 0 or
TX == 0) doesn't look wrong to me. I would prefer to add a
comment to limit a potential modification to RX and TX.

Patch

diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
index aa14a5d..f026386 100644
--- a/sound/soc/fsl/fsl_ssi.c
+++ b/sound/soc/fsl/fsl_ssi.c
@@ -417,24 +417,24 @@  static void fsl_ssi_fifo_clear(struct fsl_ssi *ssi, bool is_rx)
 }
 
 /**
- * Calculate the bits that have to be disabled for the current stream that is
- * getting disabled. This keeps the bits enabled that are necessary for the
- * second stream to work if 'stream_active' is true.
+ * Exclude bits that are used by the opposite stream
  *
- * Detailed calculation:
- * These are the values that need to be active after disabling. For non-active
- * second stream, this is 0:
- *	vals_stream * !!stream_active
+ * When both streams are active, disabling some bits for the current stream
+ * might break the other stream if these bits are used by it.
  *
- * The following computes the overall differences between the setup for the
- * to-disable stream and the active stream, a simple XOR:
- *	vals_disable ^ (vals_stream * !!(stream_active))
+ * @vals : regvals of the current stream
+ * @avals: regvals of the opposite stream
+ * @aactive: active state of the opposite stream
  *
- * The full expression adds a mask on all values we care about
+ *  1) XOR vals and avals to get the differences if the other stream is active;
+ *     Otherwise, return current vals if the other stream is not active
+ *  2) AND the result of 1) with the current vals
  */
-#define fsl_ssi_disable_val(vals_disable, vals_stream, stream_active) \
-	((vals_disable) & \
-	 ((vals_disable) ^ ((vals_stream) * (u32)!!(stream_active))))
+#define _ssi_xor_shared_bits(vals, avals, aactive) \
+	((vals) ^ ((avals) * (aactive)))
+
+#define ssi_excl_shared_bits(vals, avals, aactive) \
+	((vals) & _ssi_xor_shared_bits(vals, avals, aactive))
 
 /**
  * Enable or disable SSI configuration.
@@ -445,16 +445,10 @@  static void fsl_ssi_config(struct fsl_ssi *ssi, bool enable,
 	bool dir = (&ssi->regvals[TX] == vals) ? TX : RX;
 	struct regmap *regs = ssi->regs;
 	struct fsl_ssi_regvals *avals;
-	int nr_active_streams;
-	int keep_active;
-
-	nr_active_streams = !!(ssi->streams & BIT(TX)) +
-			    !!(ssi->streams & BIT(RX));
+	bool aactive;
 
-	if (nr_active_streams - 1 > 0)
-		keep_active = 1;
-	else
-		keep_active = 0;
+	/* Check if the opposite stream is active */
+	aactive = ssi->streams & BIT(!dir);
 
 	/* Get the opposite direction to keep its values untouched */
 	if (&ssi->regvals[RX] == vals)
@@ -467,8 +461,7 @@  static void fsl_ssi_config(struct fsl_ssi *ssi, bool enable,
 		 * To keep the other stream safe, exclude shared bits between
 		 * both streams, and get safe bits to disable current stream
 		 */
-		u32 scr = fsl_ssi_disable_val(vals->scr, avals->scr,
-					      keep_active);
+		u32 scr = ssi_excl_shared_bits(vals->scr, avals->scr, aactive);
 		/* Safely disable SCR register for the stream */
 		regmap_update_bits(regs, REG_SSI_SCR, scr, 0);
 
@@ -483,7 +476,7 @@  static void fsl_ssi_config(struct fsl_ssi *ssi, bool enable,
 	 * 2) Disable all remaining bits of both streams when last stream ends
 	 */
 	if (ssi->soc->offline_config) {
-		if ((enable && !nr_active_streams) || (!enable && !keep_active))
+		if ((enable && !ssi->streams) || (!enable && !aactive))
 			fsl_ssi_rxtx_config(ssi, enable);
 
 		goto config_done;
@@ -505,12 +498,9 @@  static void fsl_ssi_config(struct fsl_ssi *ssi, bool enable,
 		 * To keep the other stream safe, exclude shared bits between
 		 * both streams, and get safe bits to disable current stream
 		 */
-		sier = fsl_ssi_disable_val(vals->sier, avals->sier,
-					   keep_active);
-		srcr = fsl_ssi_disable_val(vals->srcr, avals->srcr,
-					   keep_active);
-		stcr = fsl_ssi_disable_val(vals->stcr, avals->stcr,
-					   keep_active);
+		sier = ssi_excl_shared_bits(vals->sier, avals->sier, aactive);
+		srcr = ssi_excl_shared_bits(vals->srcr, avals->srcr, aactive);
+		stcr = ssi_excl_shared_bits(vals->stcr, avals->stcr, aactive);
 
 		/* Safely disable other control registers for the stream */
 		regmap_update_bits(regs, REG_SSI_SRCR, srcr, 0);