linux-kernel - RE: [PATCH 6/7] iio: adc: ad485x: add ad485x driver

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Message-ID:
 <CY4PR03MB33996A380953651B290EC3839B722@CY4PR03MB3399.namprd03.prod.outlook.com>
Date: Fri, 4 Oct 2024 14:07:37 +0000
From: "Miclaus, Antoniu" <Antoniu.Miclaus@...log.com>
To: David Lechner <dlechner@...libre.com>, Andy Shevchenko <andy@...nel.org>
CC: Jonathan Cameron <jic23@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>,
        "Hennerich, Michael" <Michael.Hennerich@...log.com>,
        Rob Herring
	<robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley
	<conor+dt@...nel.org>, "Sa, Nuno" <Nuno.Sa@...log.com>,
        Olivier Moysan
	<olivier.moysan@...s.st.com>,
        Uwe Kleine-König
	<ukleinek@...nel.org>,
        "Schmitt, Marcelo" <Marcelo.Schmitt@...log.com>,
        João Paulo Gonçalves <joao.goncalves@...adex.com>,
        Mike Looijmans <mike.looijmans@...ic.nl>,
        Dumitru Ceclan
	<mitrutzceclan@...il.com>,
        AngeloGioacchino Del Regno
	<angelogioacchino.delregno@...labora.com>,
        Alisa-Dariana Roman
	<alisadariana@...il.com>,
        "Cuciurean, Sergiu" <Sergiu.Cuciurean@...log.com>,
        "Bogdan, Dragos" <Dragos.Bogdan@...log.com>,
        "linux-iio@...r.kernel.org"
	<linux-iio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>,
        "linux-pwm@...r.kernel.org"
	<linux-pwm@...r.kernel.org>
Subject: RE: [PATCH 6/7] iio: adc: ad485x: add ad485x driver

> On 10/3/24 5:14 AM, Miclaus, Antoniu wrote:
> >> On 10/1/24 8:51 AM, Miclaus, Antoniu wrote:
> >>>>> Regarding the bulk writes/reads, the msb/mid/lsb registers need to be
> >>>>> read/write in a specific order and the addresses are not incremental,
> >>>>
> >>>> We have _noinc() variants of regmap accessors.
> >>> [Miclaus, Antoniu]
> >>> I think _noinc() functions read from the same register address so it doesn't
> >>> apply.
> >>> I am reading values from multiple register addresses that are not reg_addr,
> >>> reg_addr+1, reg_addr+2.
> >>
> >> I'm confused by the statement that the registers are not incremental.
> >>
> >> For example, this patch defines...
> >>
> >> +#define AD485X_REG_CHX_OFFSET_LSB(ch)
> >> 	AD485X_REG_CHX_OFFSET(ch)
> >> +#define AD485X_REG_CHX_OFFSET_MID(ch)
> >> 	(AD485X_REG_CHX_OFFSET_LSB(ch) + 0x01)
> >> +#define AD485X_REG_CHX_OFFSET_MSB(ch)
> >> 	(AD485X_REG_CHX_OFFSET_MID(ch) + 0x01)
> >>
> >> This looks exactly like reg_addr, reg_addr+1, reg_addr+2 to me.
> > Yes you are right. Although I tested with hardware and it seems that the
> registers
> > are not properly written when using bulk operations. My guess is that
> holding CS low during
> > the entire transaction might be a possible issue. Any suggestions are
> appreciated.
> 
> Is ADDR_DIR in SPI_CONFIG_A set to the correct value to match how
> the regmap is configured for bulk writes?
> 
> I had to set this bit for AD4695 which has a similar register map
> (although on that one I used two regmaps, an 8-bit one and a 16-bit
> one, instead of doing bulk operations on the 8-bit one).
> 
Thanks for the input! I tried your suggested approach: set the ADDR_DIR
to 1 during probe. Unfortunately, this did not fix the issue. I am still not able
to perform bulk writes properly to the device.

For now I will keep the only working version in v2, since there will be
most probably  other iterations of the this patch series 😊.

> >
> >>>
> >>>>> so I am not sure how the bulk functions fit. On this matter, we will need
> >>>>> unsigned int (not u8) to store the values read via regmap_read, and in
> this
> >>>>> case we will need extra casts and assignments to use get_unaligned.
> >>>>
> >>>> --
> >>>> With Best Regards,
> >>>> Andy Shevchenko
> >>>>
> >>>
> >