On Mon, Nov 20, 2017 at 11:16:07PM +0100, Maciej S. Szmigiero wrote:
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
static unsigned short fsl_ssi_ac97_read(struct snd_ac97 *ac97, @@ -1287,16 +1295,18 @@ 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;
It will return val (== 0) in this case. Will this be correctly handled by callers? I find sound/ac97/bus.c checks if ret < 0 for ops->read().
So it might be better to add "val = ret;" before goto? Or use val instead of ret directly?
}
lreg = (reg & 0x7f) << 12; @@ -1311,6 +1321,8 @@ 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;
}