From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cyrille Pitchen Subject: Re: [PATCH 4/7] Documentation: mtd: add a DT property to set the latency code of Spansion memory Date: Mon, 20 Jul 2015 11:23:39 +0200 Message-ID: <55ACBE1B.6050507@atmel.com> References: <398ca9f17bda638e05e97f258fb4e6d27ac828db.1437059658.git.cyrille.pitchen@atmel.com> <201507161944.20523.marex@denx.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: , , , , , , , , , , , , , , , , , , To: Marek Vasut Return-path: In-Reply-To: <201507161944.20523.marex-ynQEQJNshbs@public.gmane.org> Sender: linux-spi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Hi Marek, Le 16/07/2015 19:44, Marek Vasut a =E9crit : > On Thursday, July 16, 2015 at 05:27:51 PM, Cyrille Pitchen wrote: >=20 > Hi! >=20 >> Both the SPI controller and the NOR flash memory need to agree on th= e >> number of dummy cycles to use for Fast Read commands. For Spansion >> memories, this number of dummy cycles is not given directly but thro= ugh a >> so called "latency code". >> The latency code can be found into the memory datasheet and depends = on the >> SPI clock frequency, the Fast Read op code and the Single/Dual Data = Rate >> mode. >=20 > Shouldn't you be able to derive the latency code from the above infor= mation, > which you already know then ? Yes I agree with you; this could have been done adding static tables in= side the driver instead of creating a new DT property dedicated to Spansion memo= ries. When I wrote this patch, I had a close look at the s25fl512s datasheet = but only overviewed few datasheets for other Spansion QSPI flash memories. So I = don't know whether a single latency code table could be shared among all Span= sion memories or many tables should be added to support different memory mod= els. That's why I've chosen to add a dedicated DT property to support Spansi= on memories as it avoids to add tables to guess the proper latency code to= be used. I thought it would be more flexible. Maybe I will remove the support of Spansion QSPI memories from this ser= ies for now. Their support can still be implemented later. Anyway, thanks for your review :) >=20 > Best regards, > Marek Vasut >=20 Best Regards, Cyrille -- To unsubscribe from this list: send the line "unsubscribe linux-spi" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html