Message-ID: <0fbe1321-cc67-4ade-8cbb-cbbaa40d2ca1@baylibre.com>
Date: Mon, 2 Sep 2024 16:03:22 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Lars-Peter Clausen <lars@...afoo.de>,
 Michael Hennerich <Michael.Hennerich@...log.com>,
 Nuno Sá <nuno.sa@...log.com>, Rob Herring
 <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>,
 Olivier Moysan <olivier.moysan@...s.st.com>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 dlechner@...libre.com
Subject: Re: [PATCH RFC 2/8] iio: backend: extend features

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@...libre.com> wrote:
>
>> From: Angelo Dureghello <adureghello@...libre.com>
>>
>> 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@...libre.com>
>> ---
>>   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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