Re: [RFC PATCH v2 08/12] spi: cadence-quadspi: read 'has-dqs' DT property

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Santhosh Kumar K <s-k6@ti.com>
Cc: <broonie@kernel.org>,  <robh@kernel.org>,  <krzk+dt@kernel.org>,
	<conor+dt@kernel.org>,  <richard@nod.at>,  <vigneshr@ti.com>,
	<tudor.ambarus@linaro.org>,  <pratyush@kernel.org>,
	 <mwalle@kernel.org>, <linux-spi@vger.kernel.org>,
	 <devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	 <linux-mtd@lists.infradead.org>, <praneeth@ti.com>,
	 <u-kumar1@ti.com>,  <p-mantena@ti.com>, <a-dutta@ti.com>
Subject: Re: [RFC PATCH v2 08/12] spi: cadence-quadspi: read 'has-dqs' DT property
Date: Thu, 05 Feb 2026 18:35:51 +0100	[thread overview]
Message-ID: <87h5rvgkjs.fsf@bootlin.com> (raw)
In-Reply-To: <20260113141617.1905039-9-s-k6@ti.com> (Santhosh Kumar K.'s message of "Tue, 13 Jan 2026 19:46:13 +0530")

On 13/01/2026 at 19:46:13 +0530, Santhosh Kumar K <s-k6@ti.com> wrote:

> Add a boolean field to struct cqspi_flash_pdata to store whether the
> attached flash device supports DQS (Data Strobe) mode. Read this from
> the 'spi-has-dqs' device tree property during flash node parsing.
>
> This is preparatory infrastructure for PHY tuning support. The field
> will be used by subsequent patches to configure read data capture timing
> with DQS enabled for improved margins in high-speed operations.
>
> Signed-off-by: Santhosh Kumar K <s-k6@ti.com>

As mentioned in my answer to the cover letter, I am not too much in
favour of this property because this is something that is somewhat
related to the chip ID, thus discoverable. I drafted something to get
rid of this property already, I will share it for opening the
discussion.

However, for now I am closing my eyes on the fact that the DQS pin might
not be wired to the controller. In this case we will need some kind of
"dqs-not-wired" DT property, that's true, but also easily manageable at
the core level later, when/if the need arises.

Thanks,
Miquèl

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