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

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Message-ID: <20180619092832.3b6c8f22@bbrezillon>
Date:   Tue, 19 Jun 2018 09:28:32 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Yogesh Narayan Gaur <yogeshnarayan.gaur@....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 Yogesh,

Could you please use a mailer that is quoting things correctly. I have
a hard time differentiating your replies from mine.

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.

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?