| Message ID | 20210122113355.32384-1-a.fatoum@pengutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] iio: adc: stm32-adc: enable timestamping for non-DMA usage | expand |
On Fri, 22 Jan 2021 12:33:55 +0100 Ahmad Fatoum <a.fatoum@pengutronix.de> wrote: > For non-DMA usage, we have an easy way to associate a timestamp with a > sample: iio_pollfunc_store_time stores a timestamp in the primary > trigger IRQ handler and stm32_adc_trigger_handler runs in the IRQ thread > to push out the buffer along with the timestamp. > > For this to work, the driver needs to register an IIO_TIMESTAMP channel. > Do this. > > For DMA, it's not as easy, because we don't push the buffers out of > stm32_adc_trigger, but out of stm32_adc_dma_buffer_done, which runs in > a tasklet scheduled after a DMA completion. > > Preferably, the DMA controller would copy us the timestamp into that buffer > as well. Until this is implemented, restrict timestamping support to > only PIO. For low-frequency sampling, PIO is probably good enough. > > Cc: Holger Assmann <has@pengutronix.de> > Acked-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com> > Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de> This patch itself is fine, but it will expose a potential bug. The buffer passed to iio_push_to_buffers_with_timestamp needs to be suitably aligned to take an 8 byte timestamp and large enough to do so. Currently, in this driver it isn't. u16 buffer[STM32_ADC_MAX_SQ]; Appears to be the same length as the channel count, and isn't 8 byte aligned. (add __aligned(8) to fix that) Could you add that fix to this patch as well? Thanks, Jonathan > --- > v1 -> v2: > - Added comment about timestamping being PIO only (Fabrice) > - Added missing DMA resource clean up in error path (Fabrice) > - Added Fabrice's Acked-by > --- > drivers/iio/adc/stm32-adc.c | 35 +++++++++++++++++++++++++++++------ > 1 file changed, 29 insertions(+), 6 deletions(-) > > diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c > index c067c994dae2..885bb514503c 100644 > --- a/drivers/iio/adc/stm32-adc.c > +++ b/drivers/iio/adc/stm32-adc.c > @@ -1718,7 +1718,7 @@ static void stm32_adc_chan_init_one(struct iio_dev *indio_dev, > } > } > > -static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) > +static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping) > { > struct device_node *node = indio_dev->dev.of_node; > struct stm32_adc *adc = iio_priv(indio_dev); > @@ -1766,6 +1766,9 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) > return -EINVAL; > } > > + if (timestamping) > + num_channels++; > + > channels = devm_kcalloc(&indio_dev->dev, num_channels, > sizeof(struct iio_chan_spec), GFP_KERNEL); > if (!channels) > @@ -1816,6 +1819,19 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) > stm32_adc_smpr_init(adc, channels[i].channel, smp); > } > > + if (timestamping) { > + struct iio_chan_spec *timestamp = &channels[scan_index]; > + > + timestamp->type = IIO_TIMESTAMP; > + timestamp->channel = -1; > + timestamp->scan_index = scan_index; > + timestamp->scan_type.sign = 's'; > + timestamp->scan_type.realbits = 64; > + timestamp->scan_type.storagebits = 64; > + > + scan_index++; > + } > + > indio_dev->num_channels = scan_index; > indio_dev->channels = channels; > > @@ -1875,6 +1891,7 @@ static int stm32_adc_probe(struct platform_device *pdev) > struct device *dev = &pdev->dev; > irqreturn_t (*handler)(int irq, void *p) = NULL; > struct stm32_adc *adc; > + bool timestamping = false; > int ret; > > if (!pdev->dev.of_node) > @@ -1931,16 +1948,22 @@ static int stm32_adc_probe(struct platform_device *pdev) > if (ret < 0) > return ret; > > - ret = stm32_adc_chan_of_init(indio_dev); > - if (ret < 0) > - return ret; > - > ret = stm32_adc_dma_request(dev, indio_dev); > if (ret < 0) > return ret; > > - if (!adc->dma_chan) > + if (!adc->dma_chan) { > + /* For PIO mode only, iio_pollfunc_store_time stores a timestamp > + * in the primary trigger IRQ handler and stm32_adc_trigger_handler > + * runs in the IRQ thread to push out buffer along with timestamp. > + */ > handler = &stm32_adc_trigger_handler; > + timestamping = true; > + } > + > + ret = stm32_adc_chan_of_init(indio_dev, timestamping); > + if (ret < 0) > + goto err_dma_disable; > > ret = iio_triggered_buffer_setup(indio_dev, > &iio_pollfunc_store_time, handler,
Hello Jonathan, On 24.01.21 16:22, Jonathan Cameron wrote: > On Fri, 22 Jan 2021 12:33:55 +0100 > Ahmad Fatoum <a.fatoum@pengutronix.de> wrote: > >> For non-DMA usage, we have an easy way to associate a timestamp with a >> sample: iio_pollfunc_store_time stores a timestamp in the primary >> trigger IRQ handler and stm32_adc_trigger_handler runs in the IRQ thread >> to push out the buffer along with the timestamp. >> >> For this to work, the driver needs to register an IIO_TIMESTAMP channel. >> Do this. >> >> For DMA, it's not as easy, because we don't push the buffers out of >> stm32_adc_trigger, but out of stm32_adc_dma_buffer_done, which runs in >> a tasklet scheduled after a DMA completion. >> >> Preferably, the DMA controller would copy us the timestamp into that buffer >> as well. Until this is implemented, restrict timestamping support to >> only PIO. For low-frequency sampling, PIO is probably good enough. >> >> Cc: Holger Assmann <has@pengutronix.de> >> Acked-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com> >> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de> > > This patch itself is fine, but it will expose a potential bug. > > The buffer passed to iio_push_to_buffers_with_timestamp needs to be suitably > aligned to take an 8 byte timestamp and large enough to do so. > Currently, in this driver it isn't. > u16 buffer[STM32_ADC_MAX_SQ]; > Appears to be the same length as the channel count, and isn't 8 byte > aligned. (add __aligned(8) to fix that) > > Could you add that fix to this patch as well? Just done so, thanks. But I think it's very surprising API to expect a void * to have a specific alignment. Should this perhaps be encoded into the function signature? e.g. typedef void __aligned_u64_void __aligned(8); static inline int iio_push_to_buffers_with_timestamp(struct iio_dev *indio_dev, __aligned_u64_void *data, int64_t timestamp); [I assume put_unaligned_* isn't used for performance reasons?) Cheers, Ahmad > > Thanks, > > Jonathan > > >> --- >> v1 -> v2: >> - Added comment about timestamping being PIO only (Fabrice) >> - Added missing DMA resource clean up in error path (Fabrice) >> - Added Fabrice's Acked-by >> --- >> drivers/iio/adc/stm32-adc.c | 35 +++++++++++++++++++++++++++++------ >> 1 file changed, 29 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c >> index c067c994dae2..885bb514503c 100644 >> --- a/drivers/iio/adc/stm32-adc.c >> +++ b/drivers/iio/adc/stm32-adc.c >> @@ -1718,7 +1718,7 @@ static void stm32_adc_chan_init_one(struct iio_dev *indio_dev, >> } >> } >> >> -static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) >> +static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping) >> { >> struct device_node *node = indio_dev->dev.of_node; >> struct stm32_adc *adc = iio_priv(indio_dev); >> @@ -1766,6 +1766,9 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) >> return -EINVAL; >> } >> >> + if (timestamping) >> + num_channels++; >> + >> channels = devm_kcalloc(&indio_dev->dev, num_channels, >> sizeof(struct iio_chan_spec), GFP_KERNEL); >> if (!channels) >> @@ -1816,6 +1819,19 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) >> stm32_adc_smpr_init(adc, channels[i].channel, smp); >> } >> >> + if (timestamping) { >> + struct iio_chan_spec *timestamp = &channels[scan_index]; >> + >> + timestamp->type = IIO_TIMESTAMP; >> + timestamp->channel = -1; >> + timestamp->scan_index = scan_index; >> + timestamp->scan_type.sign = 's'; >> + timestamp->scan_type.realbits = 64; >> + timestamp->scan_type.storagebits = 64; >> + >> + scan_index++; >> + } >> + >> indio_dev->num_channels = scan_index; >> indio_dev->channels = channels; >> >> @@ -1875,6 +1891,7 @@ static int stm32_adc_probe(struct platform_device *pdev) >> struct device *dev = &pdev->dev; >> irqreturn_t (*handler)(int irq, void *p) = NULL; >> struct stm32_adc *adc; >> + bool timestamping = false; >> int ret; >> >> if (!pdev->dev.of_node) >> @@ -1931,16 +1948,22 @@ static int stm32_adc_probe(struct platform_device *pdev) >> if (ret < 0) >> return ret; >> >> - ret = stm32_adc_chan_of_init(indio_dev); >> - if (ret < 0) >> - return ret; >> - >> ret = stm32_adc_dma_request(dev, indio_dev); >> if (ret < 0) >> return ret; >> >> - if (!adc->dma_chan) >> + if (!adc->dma_chan) { >> + /* For PIO mode only, iio_pollfunc_store_time stores a timestamp >> + * in the primary trigger IRQ handler and stm32_adc_trigger_handler >> + * runs in the IRQ thread to push out buffer along with timestamp. >> + */ >> handler = &stm32_adc_trigger_handler; >> + timestamping = true; >> + } >> + >> + ret = stm32_adc_chan_of_init(indio_dev, timestamping); >> + if (ret < 0) >> + goto err_dma_disable; >> >> ret = iio_triggered_buffer_setup(indio_dev, >> &iio_pollfunc_store_time, handler, > >
On Mon, 25 Jan 2021 12:21:35 +0100 Ahmad Fatoum <a.fatoum@pengutronix.de> wrote: > Hello Jonathan, > > On 24.01.21 16:22, Jonathan Cameron wrote: > > On Fri, 22 Jan 2021 12:33:55 +0100 > > Ahmad Fatoum <a.fatoum@pengutronix.de> wrote: > > > >> For non-DMA usage, we have an easy way to associate a timestamp with a > >> sample: iio_pollfunc_store_time stores a timestamp in the primary > >> trigger IRQ handler and stm32_adc_trigger_handler runs in the IRQ thread > >> to push out the buffer along with the timestamp. > >> > >> For this to work, the driver needs to register an IIO_TIMESTAMP channel. > >> Do this. > >> > >> For DMA, it's not as easy, because we don't push the buffers out of > >> stm32_adc_trigger, but out of stm32_adc_dma_buffer_done, which runs in > >> a tasklet scheduled after a DMA completion. > >> > >> Preferably, the DMA controller would copy us the timestamp into that buffer > >> as well. Until this is implemented, restrict timestamping support to > >> only PIO. For low-frequency sampling, PIO is probably good enough. > >> > >> Cc: Holger Assmann <has@pengutronix.de> > >> Acked-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com> > >> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de> > > > > This patch itself is fine, but it will expose a potential bug. > > > > The buffer passed to iio_push_to_buffers_with_timestamp needs to be suitably > > aligned to take an 8 byte timestamp and large enough to do so. > > Currently, in this driver it isn't. > > u16 buffer[STM32_ADC_MAX_SQ]; > > Appears to be the same length as the channel count, and isn't 8 byte > > aligned. (add __aligned(8) to fix that) > > > > Could you add that fix to this patch as well? > > Just done so, thanks. But I think it's very surprising API to expect a void * > to have a specific alignment. Should this perhaps be encoded into > the function signature? e.g. > > typedef void __aligned_u64_void __aligned(8); > static inline int iio_push_to_buffers_with_timestamp(struct iio_dev *indio_dev, > __aligned_u64_void *data, int64_t timestamp); > Hmm. Didn't realise you could put __aligned() on a parameter. May well make sense but we can't do it yet. There are a few left over drivers that don't yet guarantee the alignment. On some architectures that's fine. Once we've done a final pass and fixed those up, we can tidy this up. Note that we had this problem for a good 5-10 years before one report of actually running into a problem. > [I assume put_unaligned_* isn't used for performance reasons?) No, it's actually about expectations of where that buffer might go. There are lots of potential consumers and many of them can assume a fixed structure and hence assume alignment. I agree, it's a very odd ABI requirement :( Would probably have done things differently if we'd registered the built in alignment issue earlier. Jonathan > > Cheers, > Ahmad > > > > > Thanks, > > > > Jonathan > > > > > >> --- > >> v1 -> v2: > >> - Added comment about timestamping being PIO only (Fabrice) > >> - Added missing DMA resource clean up in error path (Fabrice) > >> - Added Fabrice's Acked-by > >> --- > >> drivers/iio/adc/stm32-adc.c | 35 +++++++++++++++++++++++++++++------ > >> 1 file changed, 29 insertions(+), 6 deletions(-) > >> > >> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c > >> index c067c994dae2..885bb514503c 100644 > >> --- a/drivers/iio/adc/stm32-adc.c > >> +++ b/drivers/iio/adc/stm32-adc.c > >> @@ -1718,7 +1718,7 @@ static void stm32_adc_chan_init_one(struct iio_dev *indio_dev, > >> } > >> } > >> > >> -static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) > >> +static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping) > >> { > >> struct device_node *node = indio_dev->dev.of_node; > >> struct stm32_adc *adc = iio_priv(indio_dev); > >> @@ -1766,6 +1766,9 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) > >> return -EINVAL; > >> } > >> > >> + if (timestamping) > >> + num_channels++; > >> + > >> channels = devm_kcalloc(&indio_dev->dev, num_channels, > >> sizeof(struct iio_chan_spec), GFP_KERNEL); > >> if (!channels) > >> @@ -1816,6 +1819,19 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) > >> stm32_adc_smpr_init(adc, channels[i].channel, smp); > >> } > >> > >> + if (timestamping) { > >> + struct iio_chan_spec *timestamp = &channels[scan_index]; > >> + > >> + timestamp->type = IIO_TIMESTAMP; > >> + timestamp->channel = -1; > >> + timestamp->scan_index = scan_index; > >> + timestamp->scan_type.sign = 's'; > >> + timestamp->scan_type.realbits = 64; > >> + timestamp->scan_type.storagebits = 64; > >> + > >> + scan_index++; > >> + } > >> + > >> indio_dev->num_channels = scan_index; > >> indio_dev->channels = channels; > >> > >> @@ -1875,6 +1891,7 @@ static int stm32_adc_probe(struct platform_device *pdev) > >> struct device *dev = &pdev->dev; > >> irqreturn_t (*handler)(int irq, void *p) = NULL; > >> struct stm32_adc *adc; > >> + bool timestamping = false; > >> int ret; > >> > >> if (!pdev->dev.of_node) > >> @@ -1931,16 +1948,22 @@ static int stm32_adc_probe(struct platform_device *pdev) > >> if (ret < 0) > >> return ret; > >> > >> - ret = stm32_adc_chan_of_init(indio_dev); > >> - if (ret < 0) > >> - return ret; > >> - > >> ret = stm32_adc_dma_request(dev, indio_dev); > >> if (ret < 0) > >> return ret; > >> > >> - if (!adc->dma_chan) > >> + if (!adc->dma_chan) { > >> + /* For PIO mode only, iio_pollfunc_store_time stores a timestamp > >> + * in the primary trigger IRQ handler and stm32_adc_trigger_handler > >> + * runs in the IRQ thread to push out buffer along with timestamp. > >> + */ > >> handler = &stm32_adc_trigger_handler; > >> + timestamping = true; > >> + } > >> + > >> + ret = stm32_adc_chan_of_init(indio_dev, timestamping); > >> + if (ret < 0) > >> + goto err_dma_disable; > >> > >> ret = iio_triggered_buffer_setup(indio_dev, > >> &iio_pollfunc_store_time, handler, > > > > >
diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c index c067c994dae2..885bb514503c 100644 --- a/drivers/iio/adc/stm32-adc.c +++ b/drivers/iio/adc/stm32-adc.c @@ -1718,7 +1718,7 @@ static void stm32_adc_chan_init_one(struct iio_dev *indio_dev, } } -static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) +static int stm32_adc_chan_of_init(struct iio_dev *indio_dev, bool timestamping) { struct device_node *node = indio_dev->dev.of_node; struct stm32_adc *adc = iio_priv(indio_dev); @@ -1766,6 +1766,9 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) return -EINVAL; } + if (timestamping) + num_channels++; + channels = devm_kcalloc(&indio_dev->dev, num_channels, sizeof(struct iio_chan_spec), GFP_KERNEL); if (!channels) @@ -1816,6 +1819,19 @@ static int stm32_adc_chan_of_init(struct iio_dev *indio_dev) stm32_adc_smpr_init(adc, channels[i].channel, smp); } + if (timestamping) { + struct iio_chan_spec *timestamp = &channels[scan_index]; + + timestamp->type = IIO_TIMESTAMP; + timestamp->channel = -1; + timestamp->scan_index = scan_index; + timestamp->scan_type.sign = 's'; + timestamp->scan_type.realbits = 64; + timestamp->scan_type.storagebits = 64; + + scan_index++; + } + indio_dev->num_channels = scan_index; indio_dev->channels = channels; @@ -1875,6 +1891,7 @@ static int stm32_adc_probe(struct platform_device *pdev) struct device *dev = &pdev->dev; irqreturn_t (*handler)(int irq, void *p) = NULL; struct stm32_adc *adc; + bool timestamping = false; int ret; if (!pdev->dev.of_node) @@ -1931,16 +1948,22 @@ static int stm32_adc_probe(struct platform_device *pdev) if (ret < 0) return ret; - ret = stm32_adc_chan_of_init(indio_dev); - if (ret < 0) - return ret; - ret = stm32_adc_dma_request(dev, indio_dev); if (ret < 0) return ret; - if (!adc->dma_chan) + if (!adc->dma_chan) { + /* For PIO mode only, iio_pollfunc_store_time stores a timestamp + * in the primary trigger IRQ handler and stm32_adc_trigger_handler + * runs in the IRQ thread to push out buffer along with timestamp. + */ handler = &stm32_adc_trigger_handler; + timestamping = true; + } + + ret = stm32_adc_chan_of_init(indio_dev, timestamping); + if (ret < 0) + goto err_dma_disable; ret = iio_triggered_buffer_setup(indio_dev, &iio_pollfunc_store_time, handler,