| Message ID | 1387466911-3732-6-git-send-email-bigeasy@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 19 Dec 2013, Sebastian Andrzej Siewior wrote: > The ADC driver always programs all possible ADC values and discards > them except for the value IIO asked for. On the am335x-evm the driver > programs four values and it takes 500us to gather them. Reducing the number > of conversations down to the (required) one also reduces the busy loop down > to 125us. > > This leads to another error, namely the FIFOCOUNT register is sometimes > (like one out of 10 attempts) not updated in time leading to EBUSY. > The next read has the FIFOCOUNT register updated. > Checking for the ADCSTAT register for being idle isn't a good choice either. > The problem is that if TSC is used at the same time, the HW completes the > conversation for ADC *and* before the driver noticed it, the HW begins to > perform a TSC conversation and so the driver never seen the HW idle. The > next time we would have two values in the FIFO but since the driver reads > everything we always see the current one. > So instead of polling for the IDLE bit in ADCStatus register, we should > check the FIFOCOUNT register. It should be one instead of zero because we > request one value. > > This change in turn leads to another error. Sometimes if TSC & ADC are > used together the TSC starts becoming interrupts even if nobody > actually touched the touchscreen. The interrupts seem valid because TSC's > FIFO is filled with values for each channel of the TSC. This condition stops > after a few ADC reads but will occur again. Not good. > > On top of this (even without the changes I just mentioned) there is a ADC > & TSC lockup condition which was reported to me by Jeff Lance including the > following test case: > A busy loop of "cat /sys/bus/iio/devices/iio\:device0/in_voltage4_raw" > and a mug on touch screen. With this setup, the hardware will lockup after > something between 20 minutes and it could take up to a couple of hours. > During that lockup, the ADCSTAT register says 0x30 (or 0x70) which means > STEP_ID = IDLE and FSM_BUSY = yes. That means the hardware says that it is > idle and busy at the same time which is an invalid condition. > > For all this reasons I decided to rework this TSC/ADC part and add a > handshake / synchronization here: > First the ADC signals that it needs the HW and writes a 0 mask into the > SE register. The HW (if active) will complete the current conversation > and become idle. The TSC driver will gather the values from the FIFO > (woken up by an interrupt) and won't "enable" another conversation. > Instead it will wake up the ADC driver which is already waiting. The ADC > driver will start "its" conversation and once it is done, it will > enable the TSC steps so the TSC will work again. > > After this rework I haven't observed the lockup so far. Plus the busy > loop has been reduced from 500us to 125us. > > The continues-read mode remains unchanged. > > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- > drivers/iio/adc/ti_am335x_adc.c | 64 ++++++++++++++++++++++++++---------- > drivers/mfd/ti_am335x_tscadc.c | 63 +++++++++++++++++++++++++++++------ > include/linux/mfd/ti_am335x_tscadc.h | 4 +++ Assuming nothing else has changed since the answers you gave me: Acked-by: Lee Jones <lee.jones@linaro.org> Once we have the remaining Acks I'll happily apply this patch-set.
On 12/19/2013 06:18 PM, Lee Jones wrote: > Assuming nothing else has changed since the answers you gave me: > Acked-by: Lee Jones <lee.jones@linaro.org> > > Once we have the remaining Acks I'll happily apply this patch-set. Thank you. Sebastian -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Dec 19, 2013 at 04:28:31PM +0100, Sebastian Andrzej Siewior wrote: > The ADC driver always programs all possible ADC values and discards > them except for the value IIO asked for. On the am335x-evm the driver > programs four values and it takes 500us to gather them. Reducing the number > of conversations down to the (required) one also reduces the busy loop down > to 125us. > > This leads to another error, namely the FIFOCOUNT register is sometimes > (like one out of 10 attempts) not updated in time leading to EBUSY. > The next read has the FIFOCOUNT register updated. > Checking for the ADCSTAT register for being idle isn't a good choice either. > The problem is that if TSC is used at the same time, the HW completes the > conversation for ADC *and* before the driver noticed it, the HW begins to > perform a TSC conversation and so the driver never seen the HW idle. The > next time we would have two values in the FIFO but since the driver reads > everything we always see the current one. > So instead of polling for the IDLE bit in ADCStatus register, we should > check the FIFOCOUNT register. It should be one instead of zero because we > request one value. > > This change in turn leads to another error. Sometimes if TSC & ADC are > used together the TSC starts becoming interrupts even if nobody > actually touched the touchscreen. The interrupts seem valid because TSC's > FIFO is filled with values for each channel of the TSC. This condition stops > after a few ADC reads but will occur again. Not good. > > On top of this (even without the changes I just mentioned) there is a ADC > & TSC lockup condition which was reported to me by Jeff Lance including the > following test case: > A busy loop of "cat /sys/bus/iio/devices/iio\:device0/in_voltage4_raw" > and a mug on touch screen. With this setup, the hardware will lockup after > something between 20 minutes and it could take up to a couple of hours. > During that lockup, the ADCSTAT register says 0x30 (or 0x70) which means > STEP_ID = IDLE and FSM_BUSY = yes. That means the hardware says that it is > idle and busy at the same time which is an invalid condition. I knew about FSM messing up. But couldn't investigate thouroughly and didn't want to rework so much while adding continuous mode. Good work :) > > For all this reasons I decided to rework this TSC/ADC part and add a > handshake / synchronization here: > First the ADC signals that it needs the HW and writes a 0 mask into the > SE register. The HW (if active) will complete the current conversation > and become idle. The TSC driver will gather the values from the FIFO > (woken up by an interrupt) and won't "enable" another conversation. > Instead it will wake up the ADC driver which is already waiting. The ADC > driver will start "its" conversation and once it is done, it will > enable the TSC steps so the TSC will work again. > > After this rework I haven't observed the lockup so far. Plus the busy > loop has been reduced from 500us to 125us. > > The continues-read mode remains unchanged. For one-shot reading from ADC, the TSC is 'disabled' for that moment. Ok. But for continuous mode, reading from ADC disables TSC for that long time? If it doesn't disable the TSC, does that mean that this fix would correct the one-shot read. But the continuous mode is still prone to the FSM hanging up? > > diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c ... > @@ -329,34 +347,43 @@ static int tiadc_read_raw(struct iio_dev *indio_dev, > unsigned int fifo1count, read, stepid; > bool found = false; > u32 step_en; > - unsigned long timeout = jiffies + usecs_to_jiffies > - (IDLE_TIMEOUT * adc_dev->channels); > + unsigned long timeout; > > if (iio_buffer_enabled(indio_dev)) > return -EBUSY; > > - step_en = get_adc_step_mask(adc_dev); > + step_en = get_adc_chan_step_mask(adc_dev, chan); > + if (!step_en) > + return -EINVAL; > + > + fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT); > + while (fifo1count--) > + tiadc_readl(adc_dev, REG_FIFO1); > + Would this flush be needed ideally? Thanks Zubair -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 12/19/13 15:28, Sebastian Andrzej Siewior wrote: > The ADC driver always programs all possible ADC values and discards > them except for the value IIO asked for. On the am335x-evm the driver > programs four values and it takes 500us to gather them. Reducing the number > of conversations down to the (required) one also reduces the busy loop down > to 125us. > > This leads to another error, namely the FIFOCOUNT register is sometimes > (like one out of 10 attempts) not updated in time leading to EBUSY. > The next read has the FIFOCOUNT register updated. > Checking for the ADCSTAT register for being idle isn't a good choice either. > The problem is that if TSC is used at the same time, the HW completes the > conversation for ADC *and* before the driver noticed it, the HW begins to > perform a TSC conversation and so the driver never seen the HW idle. The > next time we would have two values in the FIFO but since the driver reads > everything we always see the current one. > So instead of polling for the IDLE bit in ADCStatus register, we should > check the FIFOCOUNT register. It should be one instead of zero because we > request one value. > > This change in turn leads to another error. Sometimes if TSC & ADC are > used together the TSC starts becoming interrupts even if nobody becoming -> generating? > actually touched the touchscreen. The interrupts seem valid because TSC's > FIFO is filled with values for each channel of the TSC. This condition stops > after a few ADC reads but will occur again. Not good. > > On top of this (even without the changes I just mentioned) there is a ADC > & TSC lockup condition which was reported to me by Jeff Lance including the > following test case: > A busy loop of "cat /sys/bus/iio/devices/iio\:device0/in_voltage4_raw" > and a mug on touch screen. With this setup, the hardware will lockup after > something between 20 minutes and it could take up to a couple of hours. > During that lockup, the ADCSTAT register says 0x30 (or 0x70) which means > STEP_ID = IDLE and FSM_BUSY = yes. That means the hardware says that it is > idle and busy at the same time which is an invalid condition. > yikes. > For all this reasons I decided to rework this TSC/ADC part and add a > handshake / synchronization here: > First the ADC signals that it needs the HW and writes a 0 mask into the > SE register. The HW (if active) will complete the current conversation > and become idle. The TSC driver will gather the values from the FIFO > (woken up by an interrupt) and won't "enable" another conversation. > Instead it will wake up the ADC driver which is already waiting. The ADC > driver will start "its" conversation and once it is done, it will > enable the TSC steps so the TSC will work again. > > After this rework I haven't observed the lockup so far. Plus the busy > loop has been reduced from 500us to 125us. > > The continues-read mode remains unchanged. > Thanks for the detailed explanation. > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Hmm. I'm not really an expert in this complex driver, but your explanation is clear and the code appears to implement what you describe. Hopefully we'll see a fix for the continuous reads as well. Fiddly little device! Acked-by: Jonathan Cameron <jic23@kernel.org> > --- > drivers/iio/adc/ti_am335x_adc.c | 64 ++++++++++++++++++++++++++---------- > drivers/mfd/ti_am335x_tscadc.c | 63 +++++++++++++++++++++++++++++------ > include/linux/mfd/ti_am335x_tscadc.h | 4 +++ > 3 files changed, 103 insertions(+), 28 deletions(-) > > diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c > index 6822b9f..31e786e 100644 > --- a/drivers/iio/adc/ti_am335x_adc.c > +++ b/drivers/iio/adc/ti_am335x_adc.c > @@ -60,6 +60,24 @@ static u32 get_adc_step_mask(struct tiadc_device *adc_dev) > return step_en; > } > > +static u32 get_adc_chan_step_mask(struct tiadc_device *adc_dev, > + struct iio_chan_spec const *chan) > +{ > + int i; > + > + for (i = 0; i < ARRAY_SIZE(adc_dev->channel_step); i++) { > + if (chan->channel == adc_dev->channel_line[i]) { > + u32 step; > + > + step = adc_dev->channel_step[i]; > + /* +1 for the charger */ > + return 1 << (step + 1); > + } > + } > + WARN_ON(1); > + return 0; > +} > + > static u32 get_adc_step_bit(struct tiadc_device *adc_dev, int chan) > { > return 1 << adc_dev->channel_step[chan]; > @@ -329,34 +347,43 @@ static int tiadc_read_raw(struct iio_dev *indio_dev, > unsigned int fifo1count, read, stepid; > bool found = false; > u32 step_en; > - unsigned long timeout = jiffies + usecs_to_jiffies > - (IDLE_TIMEOUT * adc_dev->channels); > + unsigned long timeout; > > if (iio_buffer_enabled(indio_dev)) > return -EBUSY; > > - step_en = get_adc_step_mask(adc_dev); > + step_en = get_adc_chan_step_mask(adc_dev, chan); > + if (!step_en) > + return -EINVAL; > + > + fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT); > + while (fifo1count--) > + tiadc_readl(adc_dev, REG_FIFO1); > + > am335x_tsc_se_set_once(adc_dev->mfd_tscadc, step_en); > > - /* Wait for ADC sequencer to complete sampling */ > - while (tiadc_readl(adc_dev, REG_ADCFSM) & SEQ_STATUS) { > - if (time_after(jiffies, timeout)) > + timeout = jiffies + usecs_to_jiffies > + (IDLE_TIMEOUT * adc_dev->channels); > + /* Wait for Fifo threshold interrupt */ > + while (1) { > + fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT); > + if (fifo1count) > + break; > + > + if (time_after(jiffies, timeout)) { > + am335x_tsc_se_adc_done(adc_dev->mfd_tscadc); > return -EAGAIN; > + } > } > map_val = chan->channel + TOTAL_CHANNELS; > > /* > - * When the sub-system is first enabled, > - * the sequencer will always start with the > - * lowest step (1) and continue until step (16). > - * For ex: If we have enabled 4 ADC channels and > - * currently use only 1 out of them, the > - * sequencer still configures all the 4 steps, > - * leading to 3 unwanted data. > - * Hence we need to flush out this data. > + * We check the complete FIFO. We programmed just one entry but in case > + * something went wrong we left empty handed (-EAGAIN previously) and > + * then the value apeared somehow in the FIFO we would have two entries. > + * Therefore we read every item and keep only the latest version of the > + * requested channel. > */ > - > - fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT); > for (i = 0; i < fifo1count; i++) { > read = tiadc_readl(adc_dev, REG_FIFO1); > stepid = read & FIFOREAD_CHNLID_MASK; > @@ -368,6 +395,7 @@ static int tiadc_read_raw(struct iio_dev *indio_dev, > *val = (u16) read; > } > } > + am335x_tsc_se_adc_done(adc_dev->mfd_tscadc); > > if (found == false) > return -EBUSY; > @@ -495,8 +523,8 @@ static int tiadc_resume(struct device *dev) > tiadc_writel(adc_dev, REG_CTRL, restore); > > tiadc_step_config(indio_dev); > - am335x_tsc_se_set(adc_dev->mfd_tscadc, adc_dev->buffer_en_ch_steps); > - > + am335x_tsc_se_set_cache(adc_dev->mfd_tscadc, > + adc_dev->buffer_en_ch_steps); > return 0; > } > > diff --git a/drivers/mfd/ti_am335x_tscadc.c b/drivers/mfd/ti_am335x_tscadc.c > index 157f569..d4e8604 100644 > --- a/drivers/mfd/ti_am335x_tscadc.c > +++ b/drivers/mfd/ti_am335x_tscadc.c > @@ -24,6 +24,7 @@ > #include <linux/pm_runtime.h> > #include <linux/of.h> > #include <linux/of_device.h> > +#include <linux/sched.h> > > #include <linux/mfd/ti_am335x_tscadc.h> > > @@ -48,31 +49,71 @@ static const struct regmap_config tscadc_regmap_config = { > .val_bits = 32, > }; > > -static void am335x_tsc_se_update(struct ti_tscadc_dev *tsadc) > -{ > - tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache); > -} > - > void am335x_tsc_se_set_cache(struct ti_tscadc_dev *tsadc, u32 val) > { > unsigned long flags; > > spin_lock_irqsave(&tsadc->reg_lock, flags); > - tsadc->reg_se_cache |= val; > - am335x_tsc_se_update(tsadc); > + tsadc->reg_se_cache = val; > + if (tsadc->adc_waiting) > + wake_up(&tsadc->reg_se_wait); > + else if (!tsadc->adc_in_use) > + tscadc_writel(tsadc, REG_SE, val); > + > spin_unlock_irqrestore(&tsadc->reg_lock, flags); > } > EXPORT_SYMBOL_GPL(am335x_tsc_se_set_cache); > > +static void am335x_tscadc_need_adc(struct ti_tscadc_dev *tsadc) > +{ > + DEFINE_WAIT(wait); > + u32 reg; > + > + /* > + * disable TSC steps so it does not run while the ADC is using it. If > + * write 0 while it is running (it just started or was already running) > + * then it completes all steps that were enabled and stops then. > + */ > + tscadc_writel(tsadc, REG_SE, 0); > + reg = tscadc_readl(tsadc, REG_ADCFSM); > + if (reg & SEQ_STATUS) { > + tsadc->adc_waiting = true; > + prepare_to_wait(&tsadc->reg_se_wait, &wait, > + TASK_UNINTERRUPTIBLE); > + spin_unlock_irq(&tsadc->reg_lock); > + > + schedule(); > + > + spin_lock_irq(&tsadc->reg_lock); > + finish_wait(&tsadc->reg_se_wait, &wait); > + > + reg = tscadc_readl(tsadc, REG_ADCFSM); > + WARN_ON(reg & SEQ_STATUS); > + tsadc->adc_waiting = false; > + } > + tsadc->adc_in_use = true; > +} > + > void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val) > { > + spin_lock_irq(&tsadc->reg_lock); > + am335x_tscadc_need_adc(tsadc); > + > + tscadc_writel(tsadc, REG_SE, val); > + spin_unlock_irq(&tsadc->reg_lock); > +} > +EXPORT_SYMBOL_GPL(am335x_tsc_se_set_once); > + > +void am335x_tsc_se_adc_done(struct ti_tscadc_dev *tsadc) > +{ > unsigned long flags; > > spin_lock_irqsave(&tsadc->reg_lock, flags); > - tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache | val); > + tsadc->adc_in_use = false; > + tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache); > spin_unlock_irqrestore(&tsadc->reg_lock, flags); > } > -EXPORT_SYMBOL_GPL(am335x_tsc_se_set_once); > +EXPORT_SYMBOL_GPL(am335x_tsc_se_adc_done); > > void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val) > { > @@ -80,7 +121,7 @@ void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val) > > spin_lock_irqsave(&tsadc->reg_lock, flags); > tsadc->reg_se_cache &= ~val; > - am335x_tsc_se_update(tsadc); > + tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache); > spin_unlock_irqrestore(&tsadc->reg_lock, flags); > } > EXPORT_SYMBOL_GPL(am335x_tsc_se_clr); > @@ -188,6 +229,8 @@ static int ti_tscadc_probe(struct platform_device *pdev) > } > > spin_lock_init(&tscadc->reg_lock); > + init_waitqueue_head(&tscadc->reg_se_wait); > + > pm_runtime_enable(&pdev->dev); > pm_runtime_get_sync(&pdev->dev); > > diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h > index 2fa9c06..fb96c84 100644 > --- a/include/linux/mfd/ti_am335x_tscadc.h > +++ b/include/linux/mfd/ti_am335x_tscadc.h > @@ -159,6 +159,9 @@ struct ti_tscadc_dev { > int adc_cell; /* -1 if not used */ > struct mfd_cell cells[TSCADC_CELLS]; > u32 reg_se_cache; > + bool adc_waiting; > + bool adc_in_use; > + wait_queue_head_t reg_se_wait; > spinlock_t reg_lock; > unsigned int clk_div; > > @@ -179,5 +182,6 @@ static inline struct ti_tscadc_dev *ti_tscadc_dev_get(struct platform_device *p) > void am335x_tsc_se_set_cache(struct ti_tscadc_dev *tsadc, u32 val); > void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val); > void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val); > +void am335x_tsc_se_adc_done(struct ti_tscadc_dev *tsadc); > > #endif > -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/iio/adc/ti_am335x_adc.c b/drivers/iio/adc/ti_am335x_adc.c index 6822b9f..31e786e 100644 --- a/drivers/iio/adc/ti_am335x_adc.c +++ b/drivers/iio/adc/ti_am335x_adc.c @@ -60,6 +60,24 @@ static u32 get_adc_step_mask(struct tiadc_device *adc_dev) return step_en; } +static u32 get_adc_chan_step_mask(struct tiadc_device *adc_dev, + struct iio_chan_spec const *chan) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(adc_dev->channel_step); i++) { + if (chan->channel == adc_dev->channel_line[i]) { + u32 step; + + step = adc_dev->channel_step[i]; + /* +1 for the charger */ + return 1 << (step + 1); + } + } + WARN_ON(1); + return 0; +} + static u32 get_adc_step_bit(struct tiadc_device *adc_dev, int chan) { return 1 << adc_dev->channel_step[chan]; @@ -329,34 +347,43 @@ static int tiadc_read_raw(struct iio_dev *indio_dev, unsigned int fifo1count, read, stepid; bool found = false; u32 step_en; - unsigned long timeout = jiffies + usecs_to_jiffies - (IDLE_TIMEOUT * adc_dev->channels); + unsigned long timeout; if (iio_buffer_enabled(indio_dev)) return -EBUSY; - step_en = get_adc_step_mask(adc_dev); + step_en = get_adc_chan_step_mask(adc_dev, chan); + if (!step_en) + return -EINVAL; + + fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT); + while (fifo1count--) + tiadc_readl(adc_dev, REG_FIFO1); + am335x_tsc_se_set_once(adc_dev->mfd_tscadc, step_en); - /* Wait for ADC sequencer to complete sampling */ - while (tiadc_readl(adc_dev, REG_ADCFSM) & SEQ_STATUS) { - if (time_after(jiffies, timeout)) + timeout = jiffies + usecs_to_jiffies + (IDLE_TIMEOUT * adc_dev->channels); + /* Wait for Fifo threshold interrupt */ + while (1) { + fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT); + if (fifo1count) + break; + + if (time_after(jiffies, timeout)) { + am335x_tsc_se_adc_done(adc_dev->mfd_tscadc); return -EAGAIN; + } } map_val = chan->channel + TOTAL_CHANNELS; /* - * When the sub-system is first enabled, - * the sequencer will always start with the - * lowest step (1) and continue until step (16). - * For ex: If we have enabled 4 ADC channels and - * currently use only 1 out of them, the - * sequencer still configures all the 4 steps, - * leading to 3 unwanted data. - * Hence we need to flush out this data. + * We check the complete FIFO. We programmed just one entry but in case + * something went wrong we left empty handed (-EAGAIN previously) and + * then the value apeared somehow in the FIFO we would have two entries. + * Therefore we read every item and keep only the latest version of the + * requested channel. */ - - fifo1count = tiadc_readl(adc_dev, REG_FIFO1CNT); for (i = 0; i < fifo1count; i++) { read = tiadc_readl(adc_dev, REG_FIFO1); stepid = read & FIFOREAD_CHNLID_MASK; @@ -368,6 +395,7 @@ static int tiadc_read_raw(struct iio_dev *indio_dev, *val = (u16) read; } } + am335x_tsc_se_adc_done(adc_dev->mfd_tscadc); if (found == false) return -EBUSY; @@ -495,8 +523,8 @@ static int tiadc_resume(struct device *dev) tiadc_writel(adc_dev, REG_CTRL, restore); tiadc_step_config(indio_dev); - am335x_tsc_se_set(adc_dev->mfd_tscadc, adc_dev->buffer_en_ch_steps); - + am335x_tsc_se_set_cache(adc_dev->mfd_tscadc, + adc_dev->buffer_en_ch_steps); return 0; } diff --git a/drivers/mfd/ti_am335x_tscadc.c b/drivers/mfd/ti_am335x_tscadc.c index 157f569..d4e8604 100644 --- a/drivers/mfd/ti_am335x_tscadc.c +++ b/drivers/mfd/ti_am335x_tscadc.c @@ -24,6 +24,7 @@ #include <linux/pm_runtime.h> #include <linux/of.h> #include <linux/of_device.h> +#include <linux/sched.h> #include <linux/mfd/ti_am335x_tscadc.h> @@ -48,31 +49,71 @@ static const struct regmap_config tscadc_regmap_config = { .val_bits = 32, }; -static void am335x_tsc_se_update(struct ti_tscadc_dev *tsadc) -{ - tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache); -} - void am335x_tsc_se_set_cache(struct ti_tscadc_dev *tsadc, u32 val) { unsigned long flags; spin_lock_irqsave(&tsadc->reg_lock, flags); - tsadc->reg_se_cache |= val; - am335x_tsc_se_update(tsadc); + tsadc->reg_se_cache = val; + if (tsadc->adc_waiting) + wake_up(&tsadc->reg_se_wait); + else if (!tsadc->adc_in_use) + tscadc_writel(tsadc, REG_SE, val); + spin_unlock_irqrestore(&tsadc->reg_lock, flags); } EXPORT_SYMBOL_GPL(am335x_tsc_se_set_cache); +static void am335x_tscadc_need_adc(struct ti_tscadc_dev *tsadc) +{ + DEFINE_WAIT(wait); + u32 reg; + + /* + * disable TSC steps so it does not run while the ADC is using it. If + * write 0 while it is running (it just started or was already running) + * then it completes all steps that were enabled and stops then. + */ + tscadc_writel(tsadc, REG_SE, 0); + reg = tscadc_readl(tsadc, REG_ADCFSM); + if (reg & SEQ_STATUS) { + tsadc->adc_waiting = true; + prepare_to_wait(&tsadc->reg_se_wait, &wait, + TASK_UNINTERRUPTIBLE); + spin_unlock_irq(&tsadc->reg_lock); + + schedule(); + + spin_lock_irq(&tsadc->reg_lock); + finish_wait(&tsadc->reg_se_wait, &wait); + + reg = tscadc_readl(tsadc, REG_ADCFSM); + WARN_ON(reg & SEQ_STATUS); + tsadc->adc_waiting = false; + } + tsadc->adc_in_use = true; +} + void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val) { + spin_lock_irq(&tsadc->reg_lock); + am335x_tscadc_need_adc(tsadc); + + tscadc_writel(tsadc, REG_SE, val); + spin_unlock_irq(&tsadc->reg_lock); +} +EXPORT_SYMBOL_GPL(am335x_tsc_se_set_once); + +void am335x_tsc_se_adc_done(struct ti_tscadc_dev *tsadc) +{ unsigned long flags; spin_lock_irqsave(&tsadc->reg_lock, flags); - tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache | val); + tsadc->adc_in_use = false; + tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache); spin_unlock_irqrestore(&tsadc->reg_lock, flags); } -EXPORT_SYMBOL_GPL(am335x_tsc_se_set_once); +EXPORT_SYMBOL_GPL(am335x_tsc_se_adc_done); void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val) { @@ -80,7 +121,7 @@ void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val) spin_lock_irqsave(&tsadc->reg_lock, flags); tsadc->reg_se_cache &= ~val; - am335x_tsc_se_update(tsadc); + tscadc_writel(tsadc, REG_SE, tsadc->reg_se_cache); spin_unlock_irqrestore(&tsadc->reg_lock, flags); } EXPORT_SYMBOL_GPL(am335x_tsc_se_clr); @@ -188,6 +229,8 @@ static int ti_tscadc_probe(struct platform_device *pdev) } spin_lock_init(&tscadc->reg_lock); + init_waitqueue_head(&tscadc->reg_se_wait); + pm_runtime_enable(&pdev->dev); pm_runtime_get_sync(&pdev->dev); diff --git a/include/linux/mfd/ti_am335x_tscadc.h b/include/linux/mfd/ti_am335x_tscadc.h index 2fa9c06..fb96c84 100644 --- a/include/linux/mfd/ti_am335x_tscadc.h +++ b/include/linux/mfd/ti_am335x_tscadc.h @@ -159,6 +159,9 @@ struct ti_tscadc_dev { int adc_cell; /* -1 if not used */ struct mfd_cell cells[TSCADC_CELLS]; u32 reg_se_cache; + bool adc_waiting; + bool adc_in_use; + wait_queue_head_t reg_se_wait; spinlock_t reg_lock; unsigned int clk_div; @@ -179,5 +182,6 @@ static inline struct ti_tscadc_dev *ti_tscadc_dev_get(struct platform_device *p) void am335x_tsc_se_set_cache(struct ti_tscadc_dev *tsadc, u32 val); void am335x_tsc_se_set_once(struct ti_tscadc_dev *tsadc, u32 val); void am335x_tsc_se_clr(struct ti_tscadc_dev *tsadc, u32 val); +void am335x_tsc_se_adc_done(struct ti_tscadc_dev *tsadc); #endif
The ADC driver always programs all possible ADC values and discards them except for the value IIO asked for. On the am335x-evm the driver programs four values and it takes 500us to gather them. Reducing the number of conversations down to the (required) one also reduces the busy loop down to 125us. This leads to another error, namely the FIFOCOUNT register is sometimes (like one out of 10 attempts) not updated in time leading to EBUSY. The next read has the FIFOCOUNT register updated. Checking for the ADCSTAT register for being idle isn't a good choice either. The problem is that if TSC is used at the same time, the HW completes the conversation for ADC *and* before the driver noticed it, the HW begins to perform a TSC conversation and so the driver never seen the HW idle. The next time we would have two values in the FIFO but since the driver reads everything we always see the current one. So instead of polling for the IDLE bit in ADCStatus register, we should check the FIFOCOUNT register. It should be one instead of zero because we request one value. This change in turn leads to another error. Sometimes if TSC & ADC are used together the TSC starts becoming interrupts even if nobody actually touched the touchscreen. The interrupts seem valid because TSC's FIFO is filled with values for each channel of the TSC. This condition stops after a few ADC reads but will occur again. Not good. On top of this (even without the changes I just mentioned) there is a ADC & TSC lockup condition which was reported to me by Jeff Lance including the following test case: A busy loop of "cat /sys/bus/iio/devices/iio\:device0/in_voltage4_raw" and a mug on touch screen. With this setup, the hardware will lockup after something between 20 minutes and it could take up to a couple of hours. During that lockup, the ADCSTAT register says 0x30 (or 0x70) which means STEP_ID = IDLE and FSM_BUSY = yes. That means the hardware says that it is idle and busy at the same time which is an invalid condition. For all this reasons I decided to rework this TSC/ADC part and add a handshake / synchronization here: First the ADC signals that it needs the HW and writes a 0 mask into the SE register. The HW (if active) will complete the current conversation and become idle. The TSC driver will gather the values from the FIFO (woken up by an interrupt) and won't "enable" another conversation. Instead it will wake up the ADC driver which is already waiting. The ADC driver will start "its" conversation and once it is done, it will enable the TSC steps so the TSC will work again. After this rework I haven't observed the lockup so far. Plus the busy loop has been reduced from 500us to 125us. The continues-read mode remains unchanged. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- drivers/iio/adc/ti_am335x_adc.c | 64 ++++++++++++++++++++++++++---------- drivers/mfd/ti_am335x_tscadc.c | 63 +++++++++++++++++++++++++++++------ include/linux/mfd/ti_am335x_tscadc.h | 4 +++ 3 files changed, 103 insertions(+), 28 deletions(-)