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@xxxxxxxxxxxxxx>
> Acked-by: Fabrice Gasnier <fabrice.gasnier@xxxxxxxxxxx>
> Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>
> ---
> 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
--
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