* [PATCH] i2c: at91: ensure state is restored after suspending
@ 2017-01-30 17:25 Alexandre Belloni
2017-01-30 17:44 ` Wolfram Sang
2017-02-06 14:35 ` Ludovic Desroches
0 siblings, 2 replies; 4+ messages in thread
From: Alexandre Belloni @ 2017-01-30 17:25 UTC (permalink / raw)
To: linux-arm-kernel
When going to suspend, the I2C registers may be lost because the power to
VDDcore is cut. Save them and restore them when resuming.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
---
drivers/i2c/busses/i2c-at91.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
index 0b86c6173e07..633bdd899952 100644
--- a/drivers/i2c/busses/i2c-at91.c
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -140,6 +140,12 @@ struct at91_twi_dev {
unsigned transfer_status;
struct i2c_adapter adapter;
unsigned twi_cwgr_reg;
+ struct {
+ u32 mmr;
+ u32 imr;
+ u32 fmr;
+ u32 fimr;
+ } cache;
struct at91_twi_pdata *pdata;
bool use_dma;
bool use_alt_cmd;
@@ -1172,6 +1178,15 @@ static int at91_twi_runtime_resume(struct device *dev)
static int at91_twi_suspend_noirq(struct device *dev)
{
+ struct at91_twi_dev *twi_dev = dev_get_drvdata(dev);
+
+ twi_dev->cache.mmr = at91_twi_read(twi_dev, AT91_TWI_MMR);
+ twi_dev->cache.imr = at91_twi_read(twi_dev, AT91_TWI_IMR);
+ if (twi_dev->fifo_size) {
+ twi_dev->cache.fmr = at91_twi_read(twi_dev, AT91_TWI_FMR);
+ twi_dev->cache.fimr = at91_twi_read(twi_dev, AT91_TWI_FIMR);
+ }
+
if (!pm_runtime_status_suspended(dev))
at91_twi_runtime_suspend(dev);
@@ -1180,6 +1195,7 @@ static int at91_twi_suspend_noirq(struct device *dev)
static int at91_twi_resume_noirq(struct device *dev)
{
+ struct at91_twi_dev *twi_dev = dev_get_drvdata(dev);
int ret;
if (!pm_runtime_status_suspended(dev)) {
@@ -1191,6 +1207,14 @@ static int at91_twi_resume_noirq(struct device *dev)
pm_runtime_mark_last_busy(dev);
pm_request_autosuspend(dev);
+ at91_init_twi_bus(twi_dev);
+ at91_twi_write(twi_dev, AT91_TWI_MMR, twi_dev->cache.mmr);
+ at91_twi_write(twi_dev, AT91_TWI_IER, twi_dev->cache.imr);
+ if (twi_dev->fifo_size) {
+ at91_twi_write(twi_dev, AT91_TWI_FMR, twi_dev->cache.fmr);
+ at91_twi_write(twi_dev, AT91_TWI_FIER, twi_dev->cache.fimr);
+ }
+
return 0;
}
--
2.11.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH] i2c: at91: ensure state is restored after suspending
2017-01-30 17:25 [PATCH] i2c: at91: ensure state is restored after suspending Alexandre Belloni
@ 2017-01-30 17:44 ` Wolfram Sang
2017-02-06 14:35 ` Ludovic Desroches
1 sibling, 0 replies; 4+ messages in thread
From: Wolfram Sang @ 2017-01-30 17:44 UTC (permalink / raw)
To: linux-arm-kernel
> + at91_init_twi_bus(twi_dev);
Can't this function reinit the registers to the needed values? I am not
convinced that a cache will always reflect the proper state after
resume.
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^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] i2c: at91: ensure state is restored after suspending
2017-01-30 17:25 [PATCH] i2c: at91: ensure state is restored after suspending Alexandre Belloni
2017-01-30 17:44 ` Wolfram Sang
@ 2017-02-06 14:35 ` Ludovic Desroches
2017-02-16 16:58 ` Alexandre Belloni
1 sibling, 1 reply; 4+ messages in thread
From: Ludovic Desroches @ 2017-02-06 14:35 UTC (permalink / raw)
To: linux-arm-kernel
Hi,
I add Cyrille for FIFO part.
On Mon, Jan 30, 2017 at 06:25:33PM +0100, Alexandre Belloni wrote:
> When going to suspend, the I2C registers may be lost because the power to
> VDDcore is cut. Save them and restore them when resuming.
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> ---
> drivers/i2c/busses/i2c-at91.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
> index 0b86c6173e07..633bdd899952 100644
> --- a/drivers/i2c/busses/i2c-at91.c
> +++ b/drivers/i2c/busses/i2c-at91.c
> @@ -140,6 +140,12 @@ struct at91_twi_dev {
> unsigned transfer_status;
> struct i2c_adapter adapter;
> unsigned twi_cwgr_reg;
> + struct {
> + u32 mmr;
> + u32 imr;
> + u32 fmr;
> + u32 fimr;
> + } cache;
Do we really need it?
For instance MMR is only written in at91_twi_xfer(). I am not sure we can
continue the transfer when resuming. I assume we will need to perform a new
transfer from a proper state.
Moreover at91_init_twi_bus() is called on resume, it will perform a reset and
it seems it can lead to strange behaviors:
"Note that issuing a software while transmitting might leave a slave in
an unknown state holding the TWD line. In such case, a Bus Clear Command
will allow to make the slave release the TWD line (the first frame
sent afterwards might not be received properly by the slave)."
I think fimr is useless, AT91_TWI_FIER and AT91_TWI_FIDR are not used in
the current code.
Regards
Ludovic
> struct at91_twi_pdata *pdata;
> bool use_dma;
> bool use_alt_cmd;
> @@ -1172,6 +1178,15 @@ static int at91_twi_runtime_resume(struct device *dev)
>
> static int at91_twi_suspend_noirq(struct device *dev)
> {
> + struct at91_twi_dev *twi_dev = dev_get_drvdata(dev);
> +
> + twi_dev->cache.mmr = at91_twi_read(twi_dev, AT91_TWI_MMR);
> + twi_dev->cache.imr = at91_twi_read(twi_dev, AT91_TWI_IMR);
> + if (twi_dev->fifo_size) {
> + twi_dev->cache.fmr = at91_twi_read(twi_dev, AT91_TWI_FMR);
> + twi_dev->cache.fimr = at91_twi_read(twi_dev, AT91_TWI_FIMR);
> + }
> +
> if (!pm_runtime_status_suspended(dev))
> at91_twi_runtime_suspend(dev);
>
> @@ -1180,6 +1195,7 @@ static int at91_twi_suspend_noirq(struct device *dev)
>
> static int at91_twi_resume_noirq(struct device *dev)
> {
> + struct at91_twi_dev *twi_dev = dev_get_drvdata(dev);
> int ret;
>
> if (!pm_runtime_status_suspended(dev)) {
> @@ -1191,6 +1207,14 @@ static int at91_twi_resume_noirq(struct device *dev)
> pm_runtime_mark_last_busy(dev);
> pm_request_autosuspend(dev);
>
> + at91_init_twi_bus(twi_dev);
> + at91_twi_write(twi_dev, AT91_TWI_MMR, twi_dev->cache.mmr);
> + at91_twi_write(twi_dev, AT91_TWI_IER, twi_dev->cache.imr);
> + if (twi_dev->fifo_size) {
> + at91_twi_write(twi_dev, AT91_TWI_FMR, twi_dev->cache.fmr);
> + at91_twi_write(twi_dev, AT91_TWI_FIER, twi_dev->cache.fimr);
> + }
> +
> return 0;
> }
>
> --
> 2.11.0
>
^ permalink raw reply [flat|nested] 4+ messages in thread* [PATCH] i2c: at91: ensure state is restored after suspending
2017-02-06 14:35 ` Ludovic Desroches
@ 2017-02-16 16:58 ` Alexandre Belloni
0 siblings, 0 replies; 4+ messages in thread
From: Alexandre Belloni @ 2017-02-16 16:58 UTC (permalink / raw)
To: linux-arm-kernel
On 06/02/2017 at 15:35:55 +0100, Ludovic Desroches wrote:
> On Mon, Jan 30, 2017 at 06:25:33PM +0100, Alexandre Belloni wrote:
> > When going to suspend, the I2C registers may be lost because the power to
> > VDDcore is cut. Save them and restore them when resuming.
> >
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> > ---
> > drivers/i2c/busses/i2c-at91.c | 24 ++++++++++++++++++++++++
> > 1 file changed, 24 insertions(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
> > index 0b86c6173e07..633bdd899952 100644
> > --- a/drivers/i2c/busses/i2c-at91.c
> > +++ b/drivers/i2c/busses/i2c-at91.c
> > @@ -140,6 +140,12 @@ struct at91_twi_dev {
> > unsigned transfer_status;
> > struct i2c_adapter adapter;
> > unsigned twi_cwgr_reg;
> > + struct {
> > + u32 mmr;
> > + u32 imr;
> > + u32 fmr;
> > + u32 fimr;
> > + } cache;
>
> Do we really need it?
>
> For instance MMR is only written in at91_twi_xfer(). I am not sure we can
> continue the transfer when resuming. I assume we will need to perform a new
> transfer from a proper state.
>
> Moreover at91_init_twi_bus() is called on resume, it will perform a reset and
> it seems it can lead to strange behaviors:
> "Note that issuing a software while transmitting might leave a slave in
> an unknown state holding the TWD line. In such case, a Bus Clear Command
> will allow to make the slave release the TWD line (the first frame
> sent afterwards might not be received properly by the slave)."
>
Yeah, so basically because VDDcore is cut, we are not in a position
where continuing the transfer is possible.
I would simply call at91_init_twi_bus() in resume_noirq. I think it is
the proper thing to do.
> I think fimr is useless, AT91_TWI_FIER and AT91_TWI_FIDR are not used in
> the current code.
>
You are right.
> Regards
>
> Ludovic
>
> > struct at91_twi_pdata *pdata;
> > bool use_dma;
> > bool use_alt_cmd;
> > @@ -1172,6 +1178,15 @@ static int at91_twi_runtime_resume(struct device *dev)
> >
> > static int at91_twi_suspend_noirq(struct device *dev)
> > {
> > + struct at91_twi_dev *twi_dev = dev_get_drvdata(dev);
> > +
> > + twi_dev->cache.mmr = at91_twi_read(twi_dev, AT91_TWI_MMR);
> > + twi_dev->cache.imr = at91_twi_read(twi_dev, AT91_TWI_IMR);
> > + if (twi_dev->fifo_size) {
> > + twi_dev->cache.fmr = at91_twi_read(twi_dev, AT91_TWI_FMR);
> > + twi_dev->cache.fimr = at91_twi_read(twi_dev, AT91_TWI_FIMR);
> > + }
> > +
> > if (!pm_runtime_status_suspended(dev))
> > at91_twi_runtime_suspend(dev);
> >
> > @@ -1180,6 +1195,7 @@ static int at91_twi_suspend_noirq(struct device *dev)
> >
> > static int at91_twi_resume_noirq(struct device *dev)
> > {
> > + struct at91_twi_dev *twi_dev = dev_get_drvdata(dev);
> > int ret;
> >
> > if (!pm_runtime_status_suspended(dev)) {
> > @@ -1191,6 +1207,14 @@ static int at91_twi_resume_noirq(struct device *dev)
> > pm_runtime_mark_last_busy(dev);
> > pm_request_autosuspend(dev);
> >
> > + at91_init_twi_bus(twi_dev);
> > + at91_twi_write(twi_dev, AT91_TWI_MMR, twi_dev->cache.mmr);
> > + at91_twi_write(twi_dev, AT91_TWI_IER, twi_dev->cache.imr);
> > + if (twi_dev->fifo_size) {
> > + at91_twi_write(twi_dev, AT91_TWI_FMR, twi_dev->cache.fmr);
> > + at91_twi_write(twi_dev, AT91_TWI_FIER, twi_dev->cache.fimr);
> > + }
> > +
> > return 0;
> > }
> >
> > --
> > 2.11.0
> >
--
Alexandre Belloni, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
^ permalink raw reply [flat|nested] 4+ messages in thread
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2017-01-30 17:25 [PATCH] i2c: at91: ensure state is restored after suspending Alexandre Belloni
2017-01-30 17:44 ` Wolfram Sang
2017-02-06 14:35 ` Ludovic Desroches
2017-02-16 16:58 ` Alexandre Belloni
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