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SubjectRe: [PATCH RFC 1/2] Documentation: devicetree: Add property for ignoring the dummy bits sent before read transfer
On Wed, Dec 09, 2020 at 11:27:07PM +0530, Aswath Govindraju wrote:
> Dummy zero bits are sent before data during a read transfer. This causes
> the data read to be shifted to the right. To fix this send zero bits after
> the address during a read transfer.
>
> Add property to send zero bits after the address during a read transfer.

When is this necessary? Why can't it be implied by the compatible
string which should be specific to the chip model?

>
> Suggested-by: Vignesh Raghavendra <vigneshr@ti.com>
> Signed-off-by: Aswath Govindraju <a-govindraju@ti.com>
> ---
> Documentation/devicetree/bindings/misc/eeprom-93xx46.txt | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/devicetree/bindings/misc/eeprom-93xx46.txt b/Documentation/devicetree/bindings/misc/eeprom-93xx46.txt
> index a8ebb4621f79..09fb1cec54f0 100644
> --- a/Documentation/devicetree/bindings/misc/eeprom-93xx46.txt
> +++ b/Documentation/devicetree/bindings/misc/eeprom-93xx46.txt
> @@ -10,7 +10,9 @@ Optional properties:
> - read-only : parameter-less property which disables writes to the EEPROM
> - select-gpios : if present, specifies the GPIO that will be asserted prior to
> each access to the EEPROM (e.g. for SPI bus multiplexing)
> -
> +- read-op-dummy-cycles: If present specifies the number of dummy zero-bits to
> + be sent after the address during a read transfer to ignore any bits sent
> + preceding the data.
> Property rules described in Documentation/devicetree/bindings/spi/spi-bus.txt
> apply. In particular, "reg" and "spi-max-frequency" properties must be given.
>
> --
> 2.17.1
>

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