From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0969A53E32
	for <linux-spi@vger.kernel.org>; Wed, 13 Dec 2023 17:21:42 +0000 (UTC)
Authentication-Results: smtp.subspace.kernel.org;
	dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Dgzs/7s9"
Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA5D1C433C7;
	Wed, 13 Dec 2023 17:21:39 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;
	s=k20201202; t=1702488102;
	bh=aiLJX18EHnNlc58Nl7TVW6wT31DfUmZ5+HYW3HyEo0M=;
	h=From:To:Cc:Subject:Date:In-Reply-To:References:From;
	b=Dgzs/7s9bNVI0V+kTZZnnbrWARALhf9Ix6cxo8lmrXq5Bak/55iLBsHXlebwRHFGl
	 0p+3b3pIA6v9IvNp572md58NhuB5ubafr3y5HAjdyXxDu/siiJT3PE2t6n5ucIcDs4
	 RnYWkiZQdSstMHpODZrXeXoTviJHQix+Q5pWs5Q4wfwXBNfhgYsTJvR5qLwMARN73I
	 qjF7URA8B5ymTpPA8r6N789Y5j9WZf33YgmRG7tpkbnZ54rEkUb3vLlWuUd918Zfaa
	 PLw/uzFY2yJ0dMlrPRoRPiZ6QvawQf9fZpMdAwhim+x2OM9XBHMs+ckFM2LDer3KUO
	 RTYns1u9CL2tQ==
From: Michael Walle <mwalle@kernel.org>
To: haibo.chen@nxp.com
Cc: broonie@kernel.org,
	han.xu@nxp.com,
	linux-imx@nxp.com,
	linux-spi@vger.kernel.org,
	yogeshgaur.83@gmail.com,
	Michael Walle <mwalle@kernel.org>
Subject: Re: [PATCH 4/5] spi: spi-nxp-fspi: add function to select sample clock source for flash reading
Date: Wed, 13 Dec 2023 18:21:13 +0100
Message-Id: <20231213172113.2774476-1-mwalle@kernel.org>
X-Mailer: git-send-email 2.39.2
In-Reply-To: <20231213091346.956789-4-haibo.chen@nxp.com>
References: <20231213091346.956789-4-haibo.chen@nxp.com>
Precedence: bulk
X-Mailing-List: linux-spi@vger.kernel.org
List-Id: <linux-spi.vger.kernel.org>
List-Subscribe: <mailto:linux-spi+subscribe@vger.kernel.org>
List-Unsubscribe: <mailto:linux-spi+unsubscribe@vger.kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

> From: Haibo Chen <haibo.chen@nxp.com>
> 
> fspi define four mode for sample clock source selection.
> 
> Here is the list of modes:
> mode 0: Dummy Read strobe generated by FlexSPI Controller and loopback internally
> mode 1: Dummy Read strobe generated by FlexSPI Controller and loopback from DQS pad
> mode 2: Reserved
> mode 3: Flash provided Read strobe and input from DQS pad
> 
> In default, fspi use mode 0 after reset.
> For 8-8-8-DTR mode, need to use mode 3, otherwise 8-8-8-DTR read always
> get incorrect data.

I'd say this is board dependant, right? If you now hardcode 8d8d8d
to always use mode 3. I'm not sure how a board which doesn't have
the DQS connected to the flash can change this to another mode
again. Looks like we'd need a (DT) property which tells you if
there is actually a DQS line connected to the flash.

Btw you don't check buswidth, so you'll enable that mode for any
DTR mode.

-michael