Messages in this thread | | | From | Marek Vasut <> | Subject | Re: [LINUX RFC v2 0/4] spi: add dual parallel mode support in Zynq MPSoC GQSPI controller | Date | Wed, 2 Sep 2015 20:56:09 +0200 |
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On Wednesday, September 02, 2015 at 07:12:14 PM, Ranjit Abhimanyu Waghmode wrote: > Hi Marek, > > > -----Original Message----- > > From: Marek Vasut [mailto:marex@denx.de] > > Sent: Wednesday, August 26, 2015 12:26 PM > > To: Ranjit Abhimanyu Waghmode > > Cc: dwmw2@infradead.org; computersforpeace@gmail.com; > > broonie@kernel.org; Michal Simek; Soren Brinkmann; zajec5@gmail.com; > > ben@decadent.org.uk; b32955@freescale.com; knut.wohlrab@de.bosch.com; > > juhosg@openwrt.org; beanhuo@micron.com; linux-mtd@lists.infradead.org; > > linux-kernel@vger.kernel.org; linux-spi@vger.kernel.org; linux-arm- > > kernel@lists.infradead.org; Harini Katakam; Punnaiah Choudary Kalluri > > Subject: Re: [LINUX RFC v2 0/4] spi: add dual parallel mode support in > > Zynq MPSoC GQSPI controller > > > > On Wednesday, August 26, 2015 at 08:26:03 AM, Ranjit Waghmode wrote: > > > This series adds dual parallel mode support for Zynq Ultrascale+ MPSoC > > > GQSPI controller driver. > > > > > > What is dual parallel mode? > > > --------------------------- > > > ZynqMP GQSPI controller supports Dual Parallel mode with following > > > functionalities: 1) Supporting two SPI flash memories operating in > > > parallel. 8 I/O lines. 2) Chip selects and clock are shared to both > > > the flash devices > > > 3) This mode is targeted for faster read/write speed and also doubles > > > the size 4) Commands/data can be transmitted/received from both the > > > devices(mirror), or only upper or only lower flash memory devices. > > > > > > 5) Data arrangement: > > > With stripe enabled, > > > Even bytes i.e. 0, 2, 4,... are transmitted on Lower Data Bus > > > Odd bytes i.e. 1, 3, 5,.. are transmitted on Upper Data Bus. > > > > This might be a dumb question, but why don't you just treat this as an > > SPI NOR flash with 8-bit bus ? > > In case of dual parallel configuration of this controller there are > different modes like single, dual and quad mode. Whatever you are > suggesting would fit only in the case of Quad mode operation as both buses > would have 4 lines each. In case of single mode of parallel configuration, > there would be two buses; but the line on each bus would one. So > altogether there will be two lines. And in case of dual mode of parallel > configuration each bus will be having two lines. So altogether 4 lines > will be there. So keeping 8 lines would not support above two modes of > parallel configuration correctly. > > Logically it is a single flash with 8 IO lines but physically it's a two > flash devices and each has 4 IO lines. So, in this case, read and write > addresses should be always even and minimum data that can be accessed is 2 > bytes.
Oh, I see what the issue is now. It has to do with configuring the flash into correct bus-width mode, right ?
Best regards, Marek Vasut
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