linux-kernel - RE: [PATCH 03/11] spi: Add a driver for the Freescale/NXP QuadSPI controller

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Date:   Tue, 19 Jun 2018 08:31:25 +0000
From:   Yogesh Narayan Gaur <yogeshnarayan.gaur@....com>
To:     Boris Brezillon <boris.brezillon@...tlin.com>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        Frieder Schrempf <frieder.schrempf@...eet.de>,
        "broonie@...nel.org" <broonie@...nel.org>
CC:     Fabio Estevam <fabio.estevam@....com>,
        David Wolfe <david.wolfe@....com>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "richard@....at" <richard@....at>,
        Prabhakar Kushwaha <prabhakar.kushwaha@....com>,
        Han Xu <han.xu@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>
Subject: RE: [PATCH 03/11] spi: Add a driver for the Freescale/NXP QuadSPI
 controller

Hi Boris,

> -----Original Message-----
> From: Boris Brezillon [mailto:boris.brezillon@...tlin.com]
> Sent: Tuesday, June 19, 2018 12:59 PM
> To: Yogesh Narayan Gaur <yogeshnarayan.gaur@....com>;
> marek.vasut@...il.com; Frieder Schrempf <frieder.schrempf@...eet.de>;
> broonie@...nel.org
> Cc: Fabio Estevam <fabio.estevam@....com>; David Wolfe
> <david.wolfe@....com>; dwmw2@...radead.org; richard@....at; Prabhakar
> Kushwaha <prabhakar.kushwaha@....com>; Han Xu <han.xu@....com>; linux-
> kernel@...r.kernel.org; linux-spi@...r.kernel.org; linux-
> mtd@...ts.infradead.org; miquel.raynal@...tlin.com;
> computersforpeace@...il.com
> Subject: Re: [PATCH 03/11] spi: Add a driver for the Freescale/NXP QuadSPI
> controller
> 
> Hi Yogesh,
> 
> Could you please use a mailer that is quoting things correctly. I have a hard time
> differentiating your replies from mine.

Sorry for this, have changed my mailer settings.

> 
> On Tue, 19 Jun 2018 07:10:37 +0000
> Yogesh Narayan Gaur <yogeshnarayan.gaur@....com> wrote:
> 
> > Let us take below layout of memory address space map.
> > QuadSPI Controller can access range from 0x2000_0000 - 0x2FFF_FFFF i.e. 256
> MB address space reserved and it is having 4 slave devices connected.
> > These slave devices[of size 64MB, 64MB, 32MB and 64MB ] are connected
> > at below address 0x2000_0000, 0x2400_0000, 0x2A00_0000, 0x2C00_0000
> > i.e. there is gap of 32MB from 0x2800_0000 to 0x29FF_FFFF.
> 
> Okay, I'm fine with pre-reserving 32MB per chip select.
> 
> >
> > As per my understanding of the controller, flash XX top address, register should
> have below values:
> >   QUADSPI_SFA1AD - 0x0
> >   QUADSPI_SFA2AD - 0x400_0000
> >   QUADSPI_SFB1AD - 0xA00_0000
> >   QUADSPI_SFB2AD - 0xC00_0000
> > And Register QUADSPI_SFAR should point to the range for the flash in which
> operation is happening.

My mistake values of these register would be for said case are:
QUADSPI_SFA1AD - 0x400_0000
QUADSPI_SFA2AD - 0x800_0000
QUADSPI_SFB1AD - 0xC00_0000
QUADSPI_SFB2AD - 0x1000_0000

i.e. as per controller each register is having the Top address for serial flash connected at A1/A2/B1/B2 respectively.

> 
> Wait, I thought it was supposed to be an absolute address, not one relative to
> the 0x20000000 offset.
> 
> >
> > Please check Table10-32, page 1657, in [1] for more details on flash address
> assignment.
> 
> Yes, I still don't see where it says that having one of the range with a zero size is
> forbidden, or anything mentioning a required alignment.
> 
> >
> > But say if I assign address to register QUADSPI_SFA2AD as "0 + 2 * -
> >ahb_buf_size" then this address value is not correct as per the value range
> explained in above mentioned table.
> 
> Why? If the SFA1AD is set to zero, that should not, right?
What this table says that for TOP_ADDR_MEMA1 defines the top address for flash connected at A1 and any address space between TOP_ADDR_MEMA1 and QSPI_AMBA_BASE will be routed to Serial Flash A1.
In my example case TOP_ADDR_MEMA1 is 0x400_0000
If assign value to SFAR register is "0 + 2 * ->ahb_buf_size", then this would lie in access range of Serial Flash A1 and access happens to A1 flash whereas we want access to A2 flash.

For access of serial flash A2, any address space access between TOP_ADDR_MEMA2 and TOP_ADDR_MEMA1 would be routed to serial flash A2.
Thus to access A2 flash, SFAR would be in range from 0x400_0000 and 0x800_0000

--
Regards
Yogesh Gaur