From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Udit Kumar <udit.kumar@nxp.com>
Cc: "edk2-devel@lists.01.org" <edk2-devel@lists.01.org>,
"grant.likely@linaro.org." <grant.likely@linaro.org>,
"Olivier.Martin@arm.com" <Olivier.Martin@arm.com>
Subject: Re: Storing Non volatile variables on SD/NAND
Date: Mon, 18 Sep 2017 08:43:22 -0700 [thread overview]
Message-ID: <CAKv+Gu8PzYUtmQdfCOQxeY_g_98YUhn9Mg=B=Ksvk-kn+tHBOQ@mail.gmail.com> (raw)
In-Reply-To: <AM6PR0402MB3334F65F095839DC500A1B4291630@AM6PR0402MB3334.eurprd04.prod.outlook.com>
On 18 September 2017 at 06:52, Udit Kumar <udit.kumar@nxp.com> wrote:
> Hi EDK-2 Experts,
> I am looking to store NV variables on SD/NAND device.
>
> While browsing, I came across some old post at link,
> http://feishare.com/efimail/messages/20130319-1700-Re__edk2__Regarding_storing_Boot_Device_Config_in_persistent_memory-Olivier_Martin.html
>
> Looks like, this is possible easily.
That's a bold statement dude :-)
>>> What you need to support Non-Volatile UEFI variables is a Non-Volatile Memory. And also a driver that implements the EFI Firmware Volume Block protocol for this NVM device.
>
> But MdeModulePkg does Copymem from NV variable start memory to some allocated buffers. With SD/NAND Copymem is not possible, Is this something changes since 2013 or there are some other way to use SD/NAND
>
No, SD/MMC cannot currently be used as the backing store for the EFI
variable store. The problem is that the variable protocols are
architectural protocols in PI that need to be present before any
driver model drivers are dispatched, and so putting the variable store
on block devices is not something that the PI software architecture
currently supports (unless you reimplement the whole driver stack as
DXE drivers).
On top of that, it is almost impossible to share a block device that
sits behind a controller between the firmware and the OS at runtime
(i.e., for SetVariable() calls made by efibootmgr under Linux),
because only a single agent can take ownership of the controller at
any given time. (You /could/ dedicate the SD/MMC to the firmware
entirely, and boot from SATA or USB, but this is out of the question
on most platforms that need to use SD/MMC for that variable backing
store, i.e., mobile platforms)
The best thing would be for you to convince the hardware architects in
your company to design and implement dual-ported SD/MMC controllers
that allow a single SD/MMC to have two logical views that are
independent (although I'm unsure if that is even possible in the
context of the SD/MMC specifications)
Thanks,
Ard.
next prev parent reply other threads:[~2017-09-18 15:40 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-18 13:52 Storing Non volatile variables on SD/NAND Udit Kumar
2017-09-18 15:43 ` Ard Biesheuvel [this message]
2017-09-18 16:52 ` Vladimir Olovyannikov
2017-09-19 5:28 ` Udit Kumar
2017-09-19 16:38 ` Ard Biesheuvel
2017-09-20 4:27 ` Udit Kumar
2017-09-20 4:47 ` Andrew Fish
2017-09-20 5:09 ` Udit Kumar
2017-09-20 5:17 ` Andrew Fish
2017-09-20 14:51 ` Pankaj Bansal
2017-09-20 17:34 ` Udit Kumar
2017-09-20 17:39 ` Ard Biesheuvel
2017-09-20 17:39 ` Ard Biesheuvel
2017-09-20 17:46 ` Andrew Fish
2017-10-27 9:35 ` Udit Kumar
2017-10-27 9:37 ` Udit Kumar
2017-10-27 13:20 ` Ard Biesheuvel
2017-10-27 17:46 ` Jeremy Linton
2017-10-28 3:09 ` Udit Kumar
2017-10-30 23:10 ` Jeremy Linton
2017-10-31 4:25 ` Udit Kumar
2017-09-20 17:34 ` Andrew Fish
2017-09-18 20:47 ` Jeremy Linton
2017-09-18 20:53 ` Ard Biesheuvel
2017-09-19 5:27 ` Udit Kumar
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