Messages in this thread | | | Subject | Re: [PATCH v3] iio: adc: stm32-adc: enable timestamping for non-DMA usage | From | Marc Kleine-Budde <> | Date | Mon, 25 Jan 2021 12:49:07 +0100 |
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On 1/25/21 12:21 PM, Ahmad Fatoum 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> > --- > v2 -> v3: > - explicitly specify alignment (Jonathan) > - increase buffer size to hold additional timestamp > 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 | 39 +++++++++++++++++++++++++++++-------- > 1 file changed, 31 insertions(+), 8 deletions(-) > > diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c > index c067c994dae2..ab2f440d7afb 100644 > --- a/drivers/iio/adc/stm32-adc.c > +++ b/drivers/iio/adc/stm32-adc.c > @@ -177,7 +177,7 @@ struct stm32_adc_cfg { > * @offset: ADC instance register offset in ADC block > * @cfg: compatible configuration data > * @completion: end of single conversion completion > - * @buffer: data buffer > + * @buffer: data buffer + 8 bytes for timestamp if enabled ^ > * @clk: clock for this adc instance > * @irq: interrupt for this adc instance > * @lock: spinlock > @@ -200,7 +200,7 @@ struct stm32_adc { > u32 offset; > const struct stm32_adc_cfg *cfg; > struct completion completion; > - u16 buffer[STM32_ADC_MAX_SQ]; > + u16 buffer[STM32_ADC_MAX_SQ + 8] __aligned(8); ^^ ^
How does that fit together?
Marc
-- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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