linux-kernel - Re: [PATCH V1] spi: Add support for Double Transfer Rate (DTR) mode

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Message-ID: <3aa2c190-ce4d-4805-943b-f65e98ce762c@sirena.org.uk>
Date: Wed, 26 Mar 2025 14:42:08 +0000
From: Mark Brown <broonie@...nel.org>
To: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
Cc: linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
	andersson@...nel.org, konradybcio@...nel.org
Subject: Re: [PATCH V1] spi: Add support for Double Transfer Rate (DTR) mode

On Wed, Mar 26, 2025 at 07:55:05PM +0530, Mukesh Kumar Savaliya wrote:
> On 3/26/2025 6:34 PM, Mark Brown wrote:

> > We should have a flag in the controller indicating if it supports this,
> > and code in the core which returns an error if a driver attempts to use
> > it when the controller doesn't support it.

> Have added below in spi.h which can be set by client and controller driver
> should be using it to decide mode.

> + bool        dtr_mode;

> since default it's false, should continue with SDR.
> I believe for QSPI, it supports SDR or DDR, but it's not applicable to
> standard SPI right ? So not sure in which case we should return an error ?

Standard SPI is the main thing I'm thinking of here, or possibly some
limited QSPI controller that doesn't support DTR.  It's not something
that should actually come up really, it's more error handling if things
aren't set up properly.

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