From mboxrd@z Thu Jan 1 00:00:00 1970 From: Huang Shijie Subject: Re: [PATCH v3 0/8] Add the Quadspi driver for vf610-twr Date: Thu, 12 Sep 2013 22:58:30 -0400 Message-ID: <20130913025827.GA3051@gmail.com> References: <593AEF6C47F46446852B067021A273D6D984000B@MUCSE039.lantiq.com> <20130905020435.GA3970@gmail.com> <20980858CB6D3A4BAE95CA194937D5E73EA0C7F4@DBDE04.ent.ti.com> <522817D7.1010206@freescale.com> <522D3B79.3060707@freescale.com> <52318953.6090405@freescale.com> <1378979431.2627.402.camel@shinybook.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <1378979431.2627.402.camel@shinybook.infradead.org> Sender: linux-doc-owner@vger.kernel.org To: David Woodhouse Cc: Huang Shijie , Mark Brown , "Gupta, Pekon" , "thomas.langer@lantiq.com" , "devicetree@vger.kernel.org" , "shawn.guo@linaro.org" , "b44548@freescale.com" , "dedekind1@gmail.com" , "linux-doc@vger.kernel.org" , "b18965@freescale.com" , "linux-spi@vger.kernel.org" , "linux-mtd@lists.infradead.org" , "kernel@pengutronix.de" , "lznuaa@gmail.com" , "computersforpeace@gmail.com" , "linux-arm-kernel@lists.infradead.org" List-Id: devicetree@vger.kernel.org On Thu, Sep 12, 2013 at 10:50:31AM +0100, David Woodhouse wrote: > On Thu, 2013-09-12 at 17:28 +0800, Huang Shijie wrote: > > =E4=BA=8E 2013=E5=B9=B409=E6=9C=8811=E6=97=A5 22:05, David Woodhous= e =E5=86=99=E9=81=93: > > > What*actually* happens, on the wire(s), when the flash driver as= ks the > > > SPI controller to perform a transaction? > > The LUT registers tell the controller how many wires are needed for= a=20 > > transaction. > > For example, the read status only use a single line, while the quad= read=20 > > uses 4 lines. >=20 > Is this not something that could theoretically be provided by the cal= ler > when it *makes* the transaction? >=20 > Conceptually speaking, could it not be an additional argument to > spi_write_then_read() ?=20 >=20 > After all, it's the *device* driver (m25p80.c etc.) which will know w= hat > the transaction actually *is*, and how many lines the device will wan= t > to use for each transaction? yes. we can set the lines information in the spi_write_then_read(). But for the quadspi driver, it does not need this information. When the drivers knows that it is a Quad-read transaction, it will uses the relative LUT sequence which uses the 4 lines. thanks Huang Shijie