From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cyrille Pitchen Subject: Re: [PATCH v2 2/2] doc: dt: mtd: add a DT property to enable the use of 4byte-address op codes Date: Wed, 23 Mar 2016 16:08:58 +0100 Message-ID: <56F2B18A.3020107@atmel.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring , Brian Norris Cc: "linux-mtd@lists.infradead.org" , Nicolas Ferre , boris brezillon , =?UTF-8?Q?Marek_Va=c5=a1ut?= , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala List-Id: devicetree@vger.kernel.org Hi Rob, sorry I've sent v3 at the same time as you answered to v2. I'll take your comments into account for v4. Brian, any preference between 4byte-opcodes or m25p-4byte-opcodes? Best regards, Cyrille Le 23/03/2016 13:49, Rob Herring a =C3=A9crit : > On Tue, Mar 22, 2016 at 10:13 AM, Cyrille Pitchen > wrote: >> This patch adds a new optional DT property which enables an alternat= ive >> way of supporting memory size above 16MiB (128Mib). This new mechani= sm >> translates the regular 3byte-address op codes into their 4byte-addre= ss >> version whereas the old/default mecanism makes the SPI memory enter = its >> 4byte-address mode, which has annoying side effects for early bootlo= aders. >> >> We cannot discover at run time whether the SPI NOR memory supports t= he >> 4byte-address op codes. For instance both Macronix MX25L25635E and >> MX25L25673G share the same JEDEC ID (C22019 without any extension by= te). >> However the first one doesn't support 4byte-address op codes whereas= the >> second one does. >> >> Signed-off-by: Cyrille Pitchen >> --- >> Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt | 11 ++++++= +++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt= b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt >> index 2c91c03e7eb0..8be610482089 100644 >> --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt >> +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.txt >> @@ -66,6 +66,17 @@ Optional properties: >> Refer to your chips' datasheet to check if this = is supported >> by your chip. >> >> +- m25p,4byte-opcodes: For memory size above 16MiB (128Mib), use the= dedicated >=20 > m25p is not a vendor. So drop it or m25p-4byte-opcodes. >=20 >> + 4byte-address opcodes instead of entering the= 4byte >> + address mode. This mode changes the internal = state of the >> + chip so may conflict with some early boot loa= ders, which >> + expect to use the regular (Fast) Read opcodes= with 3byte >> + address. >> + However 4byte-address opcodes are not support= ed by all >> + chips and support for them can not be detecte= d at runtime. >=20 > s/can not/cannot/ >=20 >> + Refer to you chip's datasheet to check if thi= s is >> + supported by your chip. >> + >> Example: >> >> flash: m25p80@0 { >> -- >> 1.8.2.2 >>