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ASoC: fsl_ssi: serialize AC'97 register access operations 

AC'97 register access operations (both read and write) on SSI use a one,
shared set of SSI registers for AC'97 register address and data.
This means that only one such access is possible at a time and so all these
operations need to be serialized.

Since an AC'97 register access operation in this driver takes 100us+ let's
use a mutex for this.

Use this opportunity to also change a default value returned from AC'97
register read function from -1 to 0, since that's what AC'97 specs require
to be returned when unknown / undefined registers are read.

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Maciej S. Szmigiero 2017-11-20 23:16:07 +01:00 committed by Mark Brown
parent 695b78b548
commit b880b8056b
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
1 changed files with 22 additions and 4 deletions
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26
sound/soc/fsl/fsl_ssi.c
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@ -38,6 +38,7 @@
#include <linux/ctype.h>
#include <linux/device.h>
#include <linux/delay.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/of.h>
@ -265,6 +266,8 @@ struct fsl_ssi_private {
u32 fifo_watermark;
u32 dma_maxburst;
struct mutex ac97_reg_lock;
};
/*
@ -1260,11 +1263,13 @@ static void fsl_ssi_ac97_write(struct snd_ac97 *ac97, unsigned short reg,
if (reg > 0x7f)
return;
mutex_lock(&fsl_ac97_data->ac97_reg_lock);
ret = clk_prepare_enable(fsl_ac97_data->clk);
if (ret) {
pr_err("ac97 write clk_prepare_enable failed: %d\n",
ret);
return;
goto ret_unlock;
}
lreg = reg << 12;
@ -1278,6 +1283,9 @@ static void fsl_ssi_ac97_write(struct snd_ac97 *ac97, unsigned short reg,
udelay(100);
clk_disable_unprepare(fsl_ac97_data->clk);
ret_unlock:
mutex_unlock(&fsl_ac97_data->ac97_reg_lock);
}
static unsigned short fsl_ssi_ac97_read(struct snd_ac97 *ac97,
@ -1285,16 +1293,18 @@ static unsigned short fsl_ssi_ac97_read(struct snd_ac97 *ac97,
{
struct regmap *regs = fsl_ac97_data->regs;
unsigned short val = -1;
unsigned short val = 0;
u32 reg_val;
unsigned int lreg;
int ret;
mutex_lock(&fsl_ac97_data->ac97_reg_lock);
ret = clk_prepare_enable(fsl_ac97_data->clk);
if (ret) {
pr_err("ac97 read clk_prepare_enable failed: %d\n",
ret);
return -1;
goto ret_unlock;
}
lreg = (reg & 0x7f) << 12;
@ -1309,6 +1319,8 @@ static unsigned short fsl_ssi_ac97_read(struct snd_ac97 *ac97,
clk_disable_unprepare(fsl_ac97_data->clk);
ret_unlock:
mutex_unlock(&fsl_ac97_data->ac97_reg_lock);
return val;
}
@ -1569,6 +1581,7 @@ static int fsl_ssi_probe(struct platform_device *pdev)
}
if (fsl_ssi_is_ac97(ssi_private)) {
mutex_init(&ssi_private->ac97_reg_lock);
ret = snd_soc_set_ac97_ops_of_reset(&fsl_ssi_ac97_ops, pdev);
if (ret) {
dev_err(&pdev->dev, "could not set AC'97 ops\n");
@ -1663,6 +1676,9 @@ error_asoc_register:
snd_soc_set_ac97_ops(NULL);
error_ac97_ops:
if (fsl_ssi_is_ac97(ssi_private))
mutex_destroy(&ssi_private->ac97_reg_lock);
if (ssi_private->soc->imx)
fsl_ssi_imx_clean(pdev, ssi_private);
@ -1681,8 +1697,10 @@ static int fsl_ssi_remove(struct platform_device *pdev)
if (ssi_private->soc->imx)
fsl_ssi_imx_clean(pdev, ssi_private);
if (fsl_ssi_is_ac97(ssi_private))
if (fsl_ssi_is_ac97(ssi_private)) {
snd_soc_set_ac97_ops(NULL);
mutex_destroy(&ssi_private->ac97_reg_lock);
}
return 0;
}