| Message ID | 9010cdad-4b05-d456-bf73-24cc48e38d69@maciej.szmigiero.name (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | b880b8056b31288323745a13930bc45cf4c86e9d |
| Headers | show |
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; > }
On 21.11.2017 02:52, Nicolin Chen wrote: > On Mon, Nov 20, 2017 at 11:16:07PM +0100, Maciej S. Szmigiero wrote: (..) >> 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(). Both 0 and -1 (0xffff really) are valid register values. AC'97 code that is used in companion with fsl_ssi lives in sound/pci/ac97 directory and does register reads via snd_ac97_read() function in ac97_codec.c file (located in that directory). This function has no such check. The reason why AC'97 specs call for unknown register read to return zero is that if there is some capability bit in a register then this bit is set when a CODEC has such capability. If we return -1 then it means that in this case a CODEC would be detected as having all possible capabilities that are exposed via this register (including these that aren't really supported) while if we return 0 instead then we merely wouldn't make use of some that are actually present. > > So it might be better to add "val = ret;" before goto? Or use > val instead of ret directly? Then we would be returning an error number from clk_prepare_enable() as a register value which would be almost certainly wrong. Note that this method returns unsigned short - a type with the same width as an AC'97 register, so there are no unused values in this type which could be reliably used to signify that an error had happened. Maciej
diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c index a71bb8391f61..9dea1b16de82 100644 --- a/sound/soc/fsl/fsl_ssi.c +++ b/sound/soc/fsl/fsl_ssi.c @@ -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; }; /* @@ -1262,11 +1265,13 @@ 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; @@ -1280,6 +1285,9 @@ 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, @@ -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; } 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; } @@ -1571,6 +1583,7 @@ 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"); @@ -1665,6 +1678,9 @@ static int fsl_ssi_probe(struct platform_device *pdev) 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); @@ -1683,8 +1699,10 @@ 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; }
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> --- sound/soc/fsl/fsl_ssi.c | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-)