On Thu, 10 Oct 2024 14:32:49 +0000
"Nechita, Ramona" <Ramona.Nechita@xxxxxxxxxx> wrote:
> Hello,
>
> I have some questions inline before sending out a new patch.
>
>
> ....
> >> +struct ad7779_state {
> >> + struct spi_device *spi;
> >> + const struct ad7779_chip_info *chip_info;
> >> + struct clk *mclk;
> >> + struct iio_trigger *trig;
> >> + struct completion completion;
> >> + unsigned int sampling_freq;
> >> + enum ad7779_filter filter_enabled;
> >> + /*
> >> + * DMA (thus cache coherency maintenance) requires the
> >> + * transfer buffers to live in their own cache lines.
> >> + */
> >> + struct {
> >> + u32 chans[8];
> >> + s64 timestamp;
> >
> > aligned_s64 timestamp;
> >
> >while it makes no difference in this case, this makes code aligned inside the IIO subsystem.
>
> I might be missing something but I can't find the aligned_s64 data type, should I define it myself
> in the driver?
Recent addition to the iio tree so it is in linux-next but not in mainline yet.
https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?h=togreg&id=e4ca0e59c39442546866f3dd514a3a5956577daf
It just missed last cycle.
>
> >
> >> + } data __aligned(IIO_DMA_MINALIGN);
> >
> >Note, this is different alignment to the above. And isn't the buffer below should have it instead?
While I'm here: No to this one. The s64 alignment is about
performance of CPU access + consistency across CPU architectures.
This one (which happens to always be 8 or more) is about DMA safety.
> >
> >> + u32 spidata_tx[8];
> >> + u8 reg_rx_buf[3];
> >> + u8 reg_tx_buf[3];
> >> + u8 reset_buf[8];
> >> +};
> >
> >....
> >
> >> +static int ad7779_write_raw(struct iio_dev *indio_dev,
> >> + struct iio_chan_spec const *chan, int val, int val2,
> >> + long mask)
> >
> >long? Not unsigned long?
>
> I copied the function header directly from iio.h, shouldn't it be left as such?
Hmm. That's an ancient legacy that we should really cleanup at somepoint.
Leave this as long.
>
> >
> >> +{
> >> + struct ad7779_state *st = iio_priv(indio_dev);
> >> +
> >> + iio_device_claim_direct_scoped(return -EBUSY, indio_dev) {
> >> + switch (mask) {
> >> + case IIO_CHAN_INFO_CALIBSCALE:
> >> + return ad7779_set_calibscale(st, chan->channel, val2);
> >> + case IIO_CHAN_INFO_CALIBBIAS:
> >> + return ad7779_set_calibbias(st, chan->channel, val);
> >> + case IIO_CHAN_INFO_SAMP_FREQ:
> >> + return ad7779_set_sampling_frequency(st, val);
> >> + default:
> >> + return -EINVAL;
> >> + }
> >> + }
> >> + unreachable();
> >> +}
> >
> >...
> >
> >> +static irqreturn_t ad7779_trigger_handler(int irq, void *p) {
> >> + struct iio_poll_func *pf = p;
> >> + struct iio_dev *indio_dev = pf->indio_dev;
> >> + struct ad7779_state *st = iio_priv(indio_dev);
> >> + int ret;
> >
> >...
> >
>
> Thank you!
>
> Best Regards,
> Ramona
>
