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Message-ID: <20190729172859.4374a2ad@collabora.com>
Date: Mon, 29 Jul 2019 17:28:59 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Tomer Maimon <tmaimon77@...il.com>
Cc: broonie@...nel.org, dwmw2@...radead.org,
computersforpeace@...il.com, marek.vasut@...il.com,
miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
bbrezillon@...nel.org, yogeshnarayan.gaur@....com,
tudor.ambarus@...rochip.com, gregkh@...uxfoundation.org,
frieder.schrempf@...eet.de, tglx@...utronix.de,
linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-spi@...r.kernel.org
Subject: Re: [RFC v1 0/3] *spi-mem: adding setup and callback function
Hi Tomer,
On Mon, 29 Jul 2019 17:25:01 +0300
Tomer Maimon <tmaimon77@...il.com> wrote:
> Lately we have working on Flash interface unit (FIU) SPI driver that
> using spi-mem interface, Our FIU HW module support direct Flash Rd//Wr.
>
> In our SOC (32 bit dual core ARM) we have 3 FIU's that using memory mapping as follow:
>
> FIU0 - have 2 chip select and each one have 128MB memory mapping (total 256MB memory mapping)
> FIU1 - have 4 chip select and each one have 128MB memory mapping (total 512MB memory mapping)
> FIU2 - have 4 chip select and each one have 16MB memory mapping (total 32MB memory mapping)
>
> Totally 800MB memory mapping.
>
> When the FIU driver probe it don't know the size of each Flash that
> connected to the FIU, so the entire memory mapping is allocated for each FIU
> according the FIU device tree memory map parameters.
Do you need those mappings to be active to support simple reg accesses?
> It means, if we enable all three FIU's the drivers will try to allocate totally 800MB.
>
> In 32bit system it is problematic because the kernel have only 1GB
> of memory allocation so the vmalloc cannot take 800MB.
>
> When implementing the FIU driver in the mtd/spi-nor we allocating memory address only
> for detected Flash with exact size (usually we are not using 128MB Flash), and in that case usually we allocating much less memory.
>
> To solve this issue we needed to overcome two things:
>
> 1. Get argument from the upper layer (spi-mem layer)
> 2. Calling the get argument function after SPI_NOR_SCAN function. (the MTD Flash size filled in SPI_NOR_SCAN function)
That's clearly breaking the layering we've tried to restore with the
spi-nor/spi-mem split, and I don't see why this is needed since we now
have a way to create direct mappings dynamically (with the dirmap API).
Have you tried implementing the dirmap hooks in your driver?
Regards,
Boris
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