Re: [PATCH RFC 2/8] iio: backend: extend features

[Angelo Dureghello]

Hi Jonathan,

thanks for the feedbacks,

On 31/08/24 1:23 PM, Jonathan Cameron wrote:
> On Thu, 29 Aug 2024 14:32:00 +0200
> Angelo Dureghello <adureghello@xxxxxxxxxxxx> wrote:
>
> > From: Angelo Dureghello <adureghello@xxxxxxxxxxxx>
> >
> > Extend backend features with new calls needed later on this
> > patchset from axi version of ad3552r.
> >
> > A bus type property has been added to the devicetree to
> > inform the backend about the type of bus (interface) in use
> > bu the IP.
> >
> > The follwoing calls are added:
> >
> > iio_backend_ext_sync_enable
> > 	enable synchronize channels on external trigger
> > iio_backend_ext_sync_disable
> > 	disable synchronize channels on external trigger
> > iio_backend_ddr_enable
> > 	enable ddr bus transfer
> > iio_backend_ddr_disable
> > 	disable ddr bus transfer
> > iio_backend_set_bus_mode
> > 	select the type of bus, so that specific read / write
> > 	operations are performed accordingly
> > iio_backend_buffer_enable
> > 	enable buffer
> > iio_backend_buffer_disable
> > 	disable buffer
> > iio_backend_data_transfer_addr
> > 	define the target register address where the DAC sample
> > 	will be written.
> > iio_backend_bus_reg_read
> > 	generic bus read, bus-type dependent
> > iio_backend_bus_read_write
> > 	generic bus write, bus-type dependent
> >
> > Signed-off-by: Angelo Dureghello <adureghello@xxxxxxxxxxxx>
> > ---
> >   drivers/iio/industrialio-backend.c | 151 +++++++++++++++++++++++++++++++++++++
> >   include/linux/iio/backend.h        |  24 ++++++
> >   2 files changed, 175 insertions(+)
> >
> > diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
> > index a52a6b61c8b5..1f60c8626be7 100644
> > --- a/drivers/iio/industrialio-backend.c
> > +++ b/drivers/iio/industrialio-backend.c
> > @@ -718,6 +718,157 @@ static int __devm_iio_backend_get(struct device *dev, struct iio_backend *back)
> >   	return 0;
> >   }
>
> > +
> > +/**
> > + * iio_backend_buffer_enable - Enable data buffering
> Data buffering is a very vague term.  Perhaps some more detail on what
> this means?

for this DAC IP, it is the dma buffer where i write the samples,
for other non-dac frontends may be something different, so i kept it
generic. Not sure what a proper name may be, maybe

"Enable optional data buffer" ?


> > + * @back: Backend device
> > + *
> > + * RETURNS:
> > + * 0 on success, negative error number on failure.
> > + */
> > +int iio_backend_buffer_enable(struct iio_backend *back)
> > +{
> > +	return iio_backend_op_call(back, buffer_enable);
> > +}
> > +EXPORT_SYMBOL_NS_GPL(iio_backend_buffer_enable, IIO_BACKEND);
> > +
> > +/**

> > + * iio_backend_set_buffer_disable - Disable data buffering
> > + * @back: Backend device
> > + *
> > + * RETURNS:
> > + * 0 on success, negative error number on failure.
> > + */
> > +int iio_backend_buffer_disable(struct iio_backend *back)
> > +{
> > +	return iio_backend_op_call(back, buffer_disable);
> > +}
> > +EXPORT_SYMBOL_NS_GPL(iio_backend_buffer_disable, IIO_BACKEND);
> > +
> > +/**
> > + * iio_backend_buffer_transfer_addr - Set data address.
> > + * @back: Backend device
> > + * @chan_address: Channel register address
> Run scripts/kernel-doc on this and fix the errors (parameter name is
> wrong).  W=1 builds might also point the simpler ones out.
ack, done
> > + *
> > + * Some devices may need to inform the backend about an address/location
> > + * where to read or write the data.
> I'd drop the 'location' part unless this gets used later because you
> are referring register address above.

ack, done


> > + *
> > + * RETURNS:
> > + * 0 on success, negative error number on failure.
> > + */
> > +int iio_backend_data_transfer_addr(struct iio_backend *back, u32 address)
> > +{
> > +	return iio_backend_op_call(back, data_transfer_addr, address);
> > +}
> > +EXPORT_SYMBOL_NS_GPL(iio_backend_data_transfer_addr, IIO_BACKEND);
> > +
> > +/**
> > + * iio_backend_bus_reg_read - Read from the interface bus
> > + * @back: Backend device
> > + * @reg: Register valule
> > + * @val: Pointer to register value
> > + * @size: Size, in bytes
> > + *
> > + * A backend may operate on a specific interface with a related bus.
> > + * Read from the interface bus.
> So this is effectively routing control plane data through the offloaded
> bus?  That sounds a lot more like a conventional bus than IIO backend.
> Perhaps it should be presented as that with the IIO device attached
> to that bus? I don't fully understand what is wired up here.
Mainly, an IP may include a bus as 16bit parallel, or LVDS, or similar
to QSPI as in my case (ad3552r).

In particular, the bus is physically as a QSPI bus, but the data format
over it is a bit different.

So ad3552r needs this 5 lanes bus + double data rate to reach 33MUPS.

https://analogdevicesinc.github.io/hdl/library/axi_ad3552r/index.html


> > + *
> > + * RETURNS:
> > + * 0 on success, negative error number on failure.
> > + */
> > +int iio_backend_bus_reg_read(struct iio_backend *back,
> > +			     u32 reg, void *val, size_t size)
> > +{
> > +	if (!size)
> > +		return -EINVAL;
> > +
> > +	return iio_backend_op_call(back, bus_reg_read, reg, val, size);
> > +}
> > +EXPORT_SYMBOL_NS_GPL(iio_backend_bus_reg_read, IIO_BACKEND);
> > +

Thanks a lot,

regards,
Angelo


--
 ,,,      Angelo Dureghello
:: :.     BayLibre -runtime team- Developer
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