Interesting, keep me on the cc list for stuff like this (though it's not my
sphere).
2008/12/13 Wookey <
wookey@wookware.org>
> This just appeared on linux-embedded list. Very relevant to us. If
> anyone has any comments about how it should work from balloon's POV
> then now is the time to say.
>
> ----- Forwarded message from Florian Fainelli <florian@openwrt.org> -----
>
> From: Florian Fainelli <florian@openwrt.org>
> Date: Sat, 13 Dec 2008 13:58:01 +0100
> To: Hugo Villeneuve <hugo@hugovil.com>
> Cc: linux-kernel@vger.kernel.org, linux-embedded@vger.kernel.org
> Subject: Re: FPGA programming driver architecture
> List-ID: <linux-embedded.vger.kernel.org>
> X-Spam-Status: No, score=-6.6 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED
> autolearn=ham version=3.2.3, No
>
> (CC'ing linux-embedded)
>
> Salut Hugo,
>
> Le Friday 12 December 2008 21:03:14 Hugo Villeneuve, vous avez écrit :
> > Hi,
> > I have written some code to program a FPGA in Linux, for two different
> > types of boards: one uses a serial interface (SPI) and the second a
> > parallel interface. I have been able to sucessfully program both boards.
> > I'm now trying to clean my code and make it more generic, as well as
> better
> > in line with the Linux driver model. I would also like to include it in
> the
> > mainline kernel if there is interest.
>
> Is it a platform-driver ? What do you provide in platform_data ?
>
> >
> > Here is a description of the current architecture (refer to diagrams
> > below): The fpgaload module controls one output GPIOs (PROG), and two
> input
> > GPIOs (INIT and DONE). These GPIOs are specified in board setup code.
> Both
> > fpgaload_ser and fpgaload_par modules export a single function to write a
> > byte. The fpgaload driver is a char device to which we can write
> > (/dev/fpgaload) to program a bitstream (FPGA firmware) inside the FPGA.
>
> You should probably consider using request_firmware to load the bitstream
> from
> the userspace and possibly add a /sys interface to export some attributes
> like :
>
> - GPIOs being used between the host and the FPGA
> - status (i.e : programmed, not programmed ...)
> - FPGA vendor, type ...
>
> > The
> > fpgaload driver will toggle the GPIOs to initiate programming and the
> then
> > call the corresponding write_byte function based on the interface type
> > specified in board setup code (serial or parallel, or any future
> interface
> > desired).
>
> > The problem with that approach is that when loading the fpgaload module
> > with modprobe, it will automatically try to load the fpgaload_ser and
> > fpgaload_par modules, even if only serial interface was specified in
> board
> > setup code for example. This is not good when building a kernel for
> similar
> > but different boards.
>
> What about something like that :
>
> - fpgaload-core which contains all the code that can be shared between the
> drivers like requesting firmware, providing sysfs attributes,
> - fpgaload-spi would handle the low-level SPI connection
> - fpgaload-par would handle the low-level parallel connection
>
> fpgaload-ser and par would register with fpgaload-core and they could
> register
> a fpga loading callback which is low-level specific for instance. Platform
> code would instantiate the core driver. That way, adding support for other
> loading protocols like slave serial or master serial can be done easily.
>
> >
> > Probably a better approach would be for the fpgaload_Ser and fpgaload_par
> > modules to register themselves with the fpgaload module. Then, should the
> > fpgaload module be built using a BUS driver structure? Or anyone having
> any
> > suggestions on how it should be implemented?
> --
> Best regards, Florian Fainelli
> Email : florian@openwrt.org
> http://openwrt.org
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> ----- End forwarded message -----
> Wookey
> --
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