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Thu, 29 Apr 2021 16:28:16 +0000 Received: from ssl.serverraum.org (web.serverraum.org [172.16.0.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ssl.serverraum.org (Postfix) with ESMTPSA id 9968222173; Thu, 29 Apr 2021 18:28:13 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=walle.cc; s=mail2016061301; t=1619713693; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=KgbDNNHtI08G/Bd19jixZ4ooSityYmie7rX0EBgQRDk=; b=kBkA5zcgkuCUSwxygLw883KezMw5l+6jZDLjPTXG4h5DhGO07rPZzP9g/4/bneXr4TwxYe mvYjvRkrqAnBgc/4zpAKv5h0/QMnaAMzLaXx48OhAYsI8+wfbSrjNd38WkpQm+rB2ig2Jj Yh/d9aXzSJqDTANxVBEMIobGc119c3Q= MIME-Version: 1.0 Date: Thu, 29 Apr 2021 18:28:13 +0200 From: Michael Walle To: Pratyush Yadav Cc: Tudor.Ambarus@microchip.com, nm@ti.com, kristo@kernel.org, robh+dt@kernel.org, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, broonie@kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-spi@vger.kernel.org, lokeshvutla@ti.com Subject: Re: [RFC PATCH 4/6] spi: cadence-qspi: Use PHY for DAC reads if possible In-Reply-To: <20210312101757.sqeyledbwjnpqdoy@ti.com> References: <20210311191216.7363-1-p.yadav@ti.com> <20210311191216.7363-5-p.yadav@ti.com> <2f26456e-59ff-2625-5d65-c1537052839d@microchip.com> <20210312101757.sqeyledbwjnpqdoy@ti.com> User-Agent: Roundcube Webmail/1.4.11 Message-ID: X-Sender: michael@walle.cc X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210429_092815_661391_66883740 X-CRM114-Status: GOOD ( 12.88 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org Am 2021-03-12 11:17, schrieb Pratyush Yadav: > On 12/03/21 09:13AM, Tudor.Ambarus@microchip.com wrote: >> On 3/11/21 9:12 PM, Pratyush Yadav wrote: >> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe >> > >> > Check if a read is eligible for PHY and if it is, enable PHY and DQS. >> >> DQS as in data strobe? Shouldn't the upper layer inform the QSPI >> controller >> whether DS is required or not? > > Yes, DQS as in data strobe. I need to check this again, but IIRC the > controller cannot run in PHY mode unless DS is used. Ideally the upper > layer should indeed inform the controller whether DS is > supported/in-use > or not. That can be used to decide whether PHY mode (and consequently > the DS line) is to be used or not. > > Currently there are only two flashes that use 8D-8D-8D mode (S28HS512T > and MT35XU512ABA), and both of them drive the DS line. The LS1028A datasheet explicitly states that the calibration is only used for non-DQS flashes. Which makes sense, because it just determine at which point the input data is sampled. And if the flash provides a data strobe, it already know when to sample it. What I am missing here? -michael ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/