[PATCH v2 0/1] xilinx: Add option to load environment from outside of

Vasileios Amoiridis vasileios.amoiridis at cern.ch
Wed Jun 12 17:49:46 CEST 2024 

On Wed, 2024-06-12 at 17:32 +0200, Michal Simek wrote:
> 
> 
> On 6/12/24 17:11, Vasileios Amoiridis wrote:
> > On Wed, 2024-06-12 at 16:47 +0200, Michal Simek wrote:
> > > 
> > > 
> > > On 6/12/24 15:57, Vasileios Amoiridis wrote:
> > > > On Wed, 2024-06-12 at 15:42 +0200, Michal Simek wrote:
> > > > > Hi Vasileios,
> > > > > 
> > > > > út 4. 6. 2024 v 15:21 odesílatel Vasileios Amoiridis
> > > > > <vassilisamir at gmail.com> napsal:
> > > > > > 
> > > > > > From: Vasileios Amoiridis <vasileios.amoiridis at cern.ch>
> > > > > > 
> > > > > > Changes in v2:
> > > > > >           - Remove duplication of custom hardcoded
> > > > > > env_locations[]
> > > > > > code.
> > > > > >           - Add implementation with general
> > > > > > arch_env_get_location(op,
> > > > > > prio)
> > > > > > 
> > > > > > v1:
> > > > > > https://lore.kernel.org/u-boot/20240522174738.73522-1-vassilisamir@gmail.com/
> > > > > > 
> > > > > > Vasileios Amoiridis (1):
> > > > > >     xilinx: Add option to load environment from outside of
> > > > > > boot
> > > > > > media
> > > > > > 
> > > > > >    board/xilinx/versal-net/board.c | 47 ++++++++++++++-----
> > > > > > -----
> > > > > > ----
> > > > > >    board/xilinx/versal/board.c     | 47 ++++++++++++++-----
> > > > > > -----
> > > > > > ----
> > > > > >    board/xilinx/zynq/board.c       | 49 +++++++++++++++----
> > > > > > -----
> > > > > > -----
> > > > > >    board/xilinx/zynqmp/zynqmp.c    | 55 +++++++++++++++++--
> > > > > > -----
> > > > > > -----
> > > > > > ----
> > > > > >    4 files changed, 101 insertions(+), 97 deletions(-)
> > > > > > 
> > > > > > --
> > > > > > 2.34.1
> > > > > > 
> > > > > 
> > > > > I have to remove this patch from my queue because it is
> > > > > actually
> > > > > breaking current behavior.
> > > > > CI is reporting an issue with it and I did a closer look and
> > > > > what
> > > > > is
> > > > > happening is that if one location has no valid
> > > > > data it goes and looks at another location from the list.
> > > > > 
> > > > 
> > > > But that is the desired behavior, if the environment is not in
> > > > one
> > > > location to check to the others.
> > > 
> > > That's how u-boot is written but if device doesn't exist or not
> > > accessible by
> > > u-boot it is clear that it shouldn't be used and then behavior is
> > > correct.
> > > 
> > 
> > Hmmm, how can a device be not-accessible by u-boot but u-boot still
> > tries to use it? How could that happen?
> 
> That Xilinx virtual defconfig are setup in a way that all drivers are
> enabled 
> via Kconfig but they are not present on all boards.

Ok, now I understand how that happens.
> If you look below in defconfig we are have that variables can be in
> NAND but 
> there is no NAND device on zc702 but still u-boot tries to reach nand
> and read 
> variables from it.
> 

So, the ideal scenario would be to U-Boot never try to access the
device? Because from what I see, is that since the device is not there,
U-Boot throws an error, and moves on.

> > 
> > Also, I think that this is a problem of the user, no? If for
> > example
> > you have configure ENV_IS_IN_NAND but there is no NAND device, then
> > with the patch you get a visible error that U-Boot tries to access
> > NAND which is not there.
> 
> For our platforms where you can burn boot.bin to any boot medium we
> had no 
> choice that's why code was written like that that variables are saved
> all the 
> time to boot medium.
> Also that I don't want to maintain other defconfigs for slightly
> different 
> configurations.
> On products customers should look at our all in one defconfig and
> disable things 
> which are not needed. And where variables are saved is definitely one
> of them.
> 

Well, that makes sense.

> > 
> > > If device exists and simple varibles are not yet saved there
> > > going to
> > > different
> > > device is IMHO problematic.
> > > 
> > 
> > Maybe I am still a bit confused, but I think that if you have
> > defined
> > ENV_IS_IN_QSPI and ENV_IS_IN_NAND but the environment is not there
> > then
> > the behavior that we see is actually correct. U-Boot tries:
> > 
> > a) Get env from QSPI but fails because env is not there,
> > b) Get env from NAND but fails because NAND is not there,
> > c) Get env from nowhere.
> > 
> > To me, this looks like the correct behavior. Isn't it?
> 
> This sequence is correct but what it is not correct is when you reach
> nowhere 
> and you run saveenv you can't really save variables even they can be
> saved to 
> QSPI. They can't be saved to NAND because it is not present on the
> board.
> 

This can be solved by using the env_select command (cmd/nvedit.c) no?

> The issue is that none write initial variable to QSPI that's why
> there will be 
> all the time bad CRC but location is correct.
> 
> 
> > > > 
> > > > > On Zynq it behaves like this.
> > > > > 
> > > > > MMC:   mmc at e0100000: 0
> > > > > prio 0
> > > > > Loading Environment from SPIFlash... SF: Detected n25q128a13
> > > > > with
> > > > > page
> > > > > size 256 Bytes, erase size 64 KiB, total 16 MiB
> > > > > *** Warning - bad CRC, using default environment
> > > > > 
> > > > > prio 1
> > > > > Loading Environment from NAND... *** Error - No Valid
> > > > > Environment
> > > > > Area found
> > > > > *** Warning - bad env area, using default environment
> > > > > 
> > > > > prio 2
> > > > > Loading Environment from SPIFlash... *** Warning - bad CRC,
> > > > > using
> > > > > default environment
> > > > > 
> > > > > prio 3
> > > > > Loading Environment from nowhere... OK
> > > > > 
> > > > > 
> > > > 
> > > > This is the message that we get as well when this patch is not
> > > > added.
> > > 
> > > It means you are booting out of QSPI but qspi is not accessible
> > > by u-
> > > boot. Correct?
> > > 
> > > 
> > 
> > Well, we are booting from QSPI but environment is in eMMC. In our
> > config, we have defined ENV_IS_IN_FAT and ENV_IS_NOWHERE but we
> > have
> > not defined ENV_IS_IN_QSPI.
> 
> ok.
> 
> 
> > > > > prio is my print to show where code is. Qemu boots out in
> > > > > QSPI
> > > > > boot
> > > > > mode and SPI is tried first and because
> > > > > this is xilinx_zynq_virt defconfig drivers/env locations for
> > > > > other
> > > > > devices are present too. That's why it goes over the list
> > > > > and it always ends in nowhere which never fails.
> > > > > 
> > > > > If this runs on real HW then the same behavior is visible and
> > > > > I
> > > > > don't
> > > > > think it is right.
> > > > > I think this solution should be rethought.
> > > > > In product current behavior from our code is not the best and
> > > > > current
> > > > > U-Boot implementation is not allowing
> > > > > flexibility too. We are enabling redundant variables which
> > > > > can be
> > > > > only
> > > > > on the same device but not that you have
> > > > > one copy in QSPI and second in EMMC.
> > > > > That's why I think location should be pretty much read from
> > > > > DT.
> > > > > There is options/u-boot node where location of variables
> > > > > should
> > > > > be
> > > > > described and this should replace
> > > > > env_get_location().
> > > > 
> > > > You mean that there should be some type of new U-Boot node that
> > > > describes where the environment should be located and go and
> > > > search in this device?
> > > 
> > > Not sure if node or just dt property which points where that
> > > variables are stored.
> > > 
> > > 
> > 
> > This doesn't sound too difficult to do. Still, even if this was
> > done,
> > what would the priority be for looking for the environment? For
> > now,
> > the code is written in a way to check for the environment only in
> > the
> > bootmedia. My patch added a functionality that if the environment
> > is
> > not in the bootmedia to check somewhere else. This should be the
> > order
> > also if we had this u-boot node? Check first in the bootmedia and
> > then
> > check if there is a dt property?
> 
> I don't think this is going to be that simple. Especially to support
> redundant 
> variables saved to two different devices.
> 
> 

To my understanding, I think it is enough to have a dt property that
says "emmc" or "nand" etc.. that can be read when the
env_get_location() is executed and the correct env_location is
selected. What am I missing that makes you think that it is not so
trivial?

I don't have that much experience with the U-Boot sources themselves so
my question might be stupid, I know.

> > > > > It is a lot of work that's why I think second solution is
> > > > > more
> > > > > reasonable for you which is simply create new Kconfig symbol
> > > > > to disable board env_get_location() implementation.
> > > > > 
> > > > > Thanks,
> > > > > Michal
> > > > > 
> > > > 
> > > > You mean to basically disable the board env_get_location() that
> > > > exists in board/xilinx/zynqmp/zynqmp.c for example?
> > > 
> > > yes. Something like this.
> > > 
> > > config BOARD_ENV_LOCATION
> > >          bool "Use board defined ENV location"
> > >          default y
> > >          ...
> > > 
> > > if defined (BOARD_ENV_SETUP/LOCATION)
> > > enum env_location env_get_location(enum env_operation op, int
> > > prio)
> > > {
> > > ...
> > > }
> > > endif
> > > 
> > > M
> > > 
> > > 
> > 
> > This will be accepted by you in upstream?
> 
> I think it is reasonable compromise to pretty much disable bootmode
> media 
> selection for storing variables.
> 
> Thanks,
> Michal

Ok, I can submit a v3 then.

Cheers,
Vasilis

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