[U-Boot] FAT filesystem support on SPI flash

[U-Boot] FAT filesystem support on SPI flash

[Vasili Galka]

Hi,
	
On our system, we are interested in keeping all files, including the OS image and U-Boot second stage on FAT filesystem residing on a SPI flash.

I have not found existing U-Boot support for such functionality. Have I missed it?

In any case, I'm willing to implement this, do you see it reasonable incorporating such code into U-Boot? (if it passes review of course)

I note about design: As our chip (TI's AM335x) does not support direct boot from FAT stored on SPI, I plan reserving section at the beginning of SPI flash for the first stage boot loader and having the filesystem after it.

Best,
Vasili

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[U-Boot] FAT filesystem support on SPI flash

[Wolfgang Denk]

Dear Vasili,

In message <d69e639dbb744e9ca4c7742f42c82b81@EX13.visionmap.co.il> you wrote:
> 	
> On our system, we are interested in keeping all files, including the OS image and U-Boot second stage on FAT filesystem residing on a SPI flash.
> 
> I have not found existing U-Boot support for such functionality. Have I missed it?

We do not have FAT suppot on flash devices yet.

> In any case, I'm willing to implement this, do you see it reasonable incorporating such code into U-Boot? (if it passes review of course)

I think the best way to implement this would require a two staged
approach: in the first stage, U-Boot should adapte the device driver
model we've been waiting for so long; in the second stage, the file
system support would more or less fall into place on to of the then
existing storage device drivers.

Best regards,

Wolfgang Denk

-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
When some people discover the truth, they just can't  understand  why
everybody isn't eager to hear it.

[U-Boot] FAT filesystem support on SPI flash

[Jagan Teki]

On Sun, Feb 23, 2014 at 7:07 PM, Vasili Galka <vasili@visionmap.com> wrote:
> Hi,
>
> On our system, we are interested in keeping all files, including the OS image and U-Boot second stage on FAT filesystem residing on a SPI flash.

I'm not a file-system expert, but I've a basic question like how
does/well a SPI flash(mtd) device have
FAT support on it. Generally flash file-systems were categories to do
the job right?

>
> I have not found existing U-Boot support for such functionality. Have I missed it?
>
> In any case, I'm willing to implement this, do you see it reasonable incorporating such code into U-Boot? (if it passes review of course)
>
> I note about design: As our chip (TI's AM335x) does not support direct boot from FAT stored on SPI, I plan reserving section at the beginning of SPI flash for the first stage boot loader and having the filesystem after it.

thanks!
-- 
Jagan.

[U-Boot] FAT filesystem support on SPI flash

[Vasili Galka]

Dear Wolfgang,

1. So, my understanding is that fatload/fatls/etc have only MMC/SATA
support now? No support for MTD?

2. Where can I find the description of "device driver model" you
mention? When is it planned to be adopted?

Best,
Vasili

On Sun, Feb 23, 2014 at 7:23 PM, Wolfgang Denk <wd@denx.de> wrote:
> Dear Vasili,
>
> In message <d69e639dbb744e9ca4c7742f42c82b81@EX13.visionmap.co.il> you wrote:
>>
>> On our system, we are interested in keeping all files, including the OS image and U-Boot second stage on FAT filesystem residing on a SPI flash.
>>
>> I have not found existing U-Boot support for such functionality. Have I missed it?
>
> We do not have FAT suppot on flash devices yet.
>
>> In any case, I'm willing to implement this, do you see it reasonable incorporating such code into U-Boot? (if it passes review of course)
>
> I think the best way to implement this would require a two staged
> approach: in the first stage, U-Boot should adapte the device driver
> model we've been waiting for so long; in the second stage, the file
> system support would more or less fall into place on to of the then
> existing storage device drivers.
>
> Best regards,
>
> Wolfgang Denk
>
> --
> DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
> When some people discover the truth, they just can't  understand  why
> everybody isn't eager to hear it.

[U-Boot] FAT filesystem support on SPI flash

[Vasili Galka]

Dear Jagan,

I'm not sure I fully understand your question.
SPI flash is just a medium that has sectors/pages/blocks (call it
however you want). You are free to store data with any structure you
like on it. So if you like - you can store FAT file-system on it.
That's true that maybe storing a FAT file-system that has frequent
write operations on SPI flash is not a good idea, both because of
speed and because of flash wear. But that is an entirely different
question. There are still many cases when the data does not change
frequently and FAT on SPI flash can be useful.

Best,
Vasili

On Sun, Feb 23, 2014 at 7:49 PM, Jagan Teki <jagannadh.teki@gmail.com> wrote:
> On Sun, Feb 23, 2014 at 7:07 PM, Vasili Galka <vasili@visionmap.com> wrote:
>> Hi,
>>
>> On our system, we are interested in keeping all files, including the OS image and U-Boot second stage on FAT filesystem residing on a SPI flash.
>
> I'm not a file-system expert, but I've a basic question like how
> does/well a SPI flash(mtd) device have
> FAT support on it. Generally flash file-systems were categories to do
> the job right?
>
>>
>> I have not found existing U-Boot support for such functionality. Have I missed it?
>>
>> In any case, I'm willing to implement this, do you see it reasonable incorporating such code into U-Boot? (if it passes review of course)
>>
>> I note about design: As our chip (TI's AM335x) does not support direct boot from FAT stored on SPI, I plan reserving section at the beginning of SPI flash for the first stage boot loader and having the filesystem after it.
>
> thanks!
> --
> Jagan.

[U-Boot] FAT filesystem support on SPI flash

[Tom Rini]

On Sun, Feb 23, 2014 at 01:37:53PM +0000, Vasili Galka wrote:
> Hi,
> 	
> On our system, we are interested in keeping all files, including the
> OS image and U-Boot second stage on FAT filesystem residing on a SPI
> flash.
> 
> I have not found existing U-Boot support for such functionality. Have
> I missed it?
> 
> In any case, I'm willing to implement this, do you see it reasonable
> incorporating such code into U-Boot? (if it passes review of course)
> 
> I note about design: As our chip (TI's AM335x) does not support direct
> boot from FAT stored on SPI, I plan reserving section at the beginning
> of SPI flash for the first stage boot loader and having the filesystem
> after it.

The high level suggestion is to review your design decision as this
seems rather questionable.  Today our FAT code doesn't work directly on
flash, but I imagine a day or two of hacking might allow it to work.
But FAT isn't designed to be on flash directly and you really want a
good reason to not be using a flash filesystem on SPI.

-- 
Tom
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