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

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Message-ID:
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Date: Thu, 3 Oct 2024 10:14:57 +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
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        "Schmitt, Marcelo" <Marcelo.Schmitt@...log.com>,
        João Paulo Gonçalves <joao.goncalves@...adex.com>,
        Mike Looijmans <mike.looijmans@...ic.nl>,
        Dumitru Ceclan
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        AngeloGioacchino Del Regno
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        Alisa-Dariana Roman
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        "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"
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Subject: RE: [PATCH 6/7] iio: adc: ad485x: add ad485x driver

> 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.

> >
> >>> 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
> >>
> >