On 25.01.21 12:49, Marc Kleine-Budde wrote:
> 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?
Ah indeed, that's a little longer than needed.
Thanks for catching.
>
> Marc
>
>
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