Re: [PATCH v2 00/15] qcom: smem: modernize SMEM in U-Boot

[Sumit Garg <sumit.garg@kernel.org>]

On Tue, May 05, 2026 at 02:25:01PM +0200, Casey Connolly wrote:
> 
> 
> On 05/05/2026 12:11, Sumit Garg wrote:
> > Hi Casey,
> > 
> > Thanks for the much needed re-spin of the SMEM patch-set.
> > 
> > On Mon, May 04, 2026 at 08:57:28PM +0200, Casey Connolly wrote:
> >> Smem is currently implemented a uclass in U-Boot. This carries with it
> >> some implicit limitations about how and when we can actually talk with
> >> it, since its modelled as a device.
> >>
> >> The SMEM uclass is qualcomm specific and has no other users, smem is
> >> also largely useful for parsing the memory map and other tasks which we
> >> have to do before DM is alive anyway.
> >>
> >> Let's drop the old smem code and replace it with a straight port from
> >> Linux, providing a familiar interface and enabling us to access it much
> >> earlier in the boot process than would be possible with a standard
> >> udevice.
> >>
> >> Additionally, this will be easier to maintain going forwards since any
> >> patches from Linux can be more easily ported over.
> >>
> >> With this new smem framework in place, we can now use SMEM to parse the
> >> memory map when it's not provided via some other mechanism and to read
> >> the serial number of the board.
> >>
> >> Implement this functionality and split the snapdragon memory parsing off
> >> to its own file to try and organise things a bit better.
> >>
> >> Since the memory map stored in SMEM doesn't already have some carveouts
> >> let's also be correct about unmapping reserved memory regions, we
> >> should eventually do this on all Qualcomm boards but it's particularly
> >> important when we aren't chainloading from ABL.
> > 
> > This was really needed to unmap reserved regions in U-Boot memory map to
> > increase robustness.
> 
> agreed, the ~100ms cost sucks but I hope we can bring it down by doing
> this after dcache enable if we can figure that out (would probably rely
> on starting with an initial minimal map to avoid the prefetcher issues)
> but yeah, a problem for the future for sure.

+1

> 
> > 
> >>
> >> This depends on a fix for unmapping memory regions: https://lore.kernel.org/u-boot/20260504175511.585797-1-casey.connolly@linaro.org/
> >>
> >> ---
> >> Changes in v2:
> >> - Ensure reserved regions are unmapped appropriately when using SMEM as
> >>   the source of truth for the memory map.
> >> - Support SMEM ram layout v0/v1 for older platforms using a header from
> >>   Qualcomm.
> > 
> > It would be better if you can provide proper attribution in the commit
> > to which this header is being picked up.
> 
> Where is the header sourced from? I can't really use another patch
> posting as a source.

I would have just mentioned the header to be contributed by:
Aswin Murugan <aswin.murugan@oss.qualcomm.com> in commit message.

> 
> > 
> >> - Set an environment variable (memmap_source) providing info about
> >>   where U-Boots memory map is from.
> >> - Correctly handle serial_num missing on msm8916
> >> - Link to v1: https://lore.kernel.org/r/20241124-b4-modernise-smem-v1-0-b7852c11b67c@linaro.org
> >>
> > 
> > FWIW, I tested this patch-set on RB3Gen2 and lemans-evk after dropping
> > the U-Boot DT overrides, so feel free to carry:
> 
> Good to know! I assume you removed the hardcoded DT memorymap for testing?

Yeah I did drop the hardcoded DT memory map as you can see here [1].
Feel free to skip picking up DT memory override for Lemans EVK with this
series merged.

[1] https://github.com/qualcomm-linux/u-boot/pull/56

-Sumit

> 
> > 
> > Tested-by: Sumit Garg <sumit.garg@oss.qualcomm.com>
> > 
> > I will give a proper review to this series soon.
> 
> Thanks
> > 
> > -Sumit
> > 
> >> To: u-boot@lists.denx.de
> >> To: Sumit Garg <sumit.garg@kernel.org>
> >> To: u-boot-qcom@groups.io
> >> Cc: Tom Rini <trini@konsulko.com>
> >> Cc: Simon Glass <sjg@chromium.org>
> >> Cc: Casey Connolly <casey.connolly@linaro.org>
> >> Cc: Peng Fan <peng.fan@nxp.com>
> >> Cc: Marek Vasut <marek.vasut+renesas@mailbox.org>
> >> Cc: Alice Guo <alice.guo@nxp.com>
> >> Cc: Quentin Schulz <quentin.schulz@cherry.de>
> >> Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> >> Cc: Neil Armstrong <neil.armstrong@linaro.org>
> >> Cc: Mattijs Korpershoek <mkorpershoek@kernel.org>
> >> Cc: Kuan-Wei Chiu <visitorckw@gmail.com>
> >> Cc: Raymond Mao <raymond.mao@riscstar.com>
> >> Cc: Stefan Roese <stefan.roese@mailbox.org>
> >> Cc: Philip Molloy <philip.molloy@analog.com>
> >> Cc: Jerome Forissier <jerome.forissier@arm.com>
> >> Cc: Marek Vasut <marek.vasut@mailbox.org>
> >> Cc: Varadarajan Narayanan <varadarajan.narayanan@oss.qualcomm.com>
> >> Cc: Patrice Chotard <patrice.chotard@foss.st.com>
> >> Cc: Aswin Murugan <aswin.murugan@oss.qualcomm.com>
> >> Cc: Rasmus Villemoes <ravi@prevas.dk>
> >> Cc: Heiko Schocher <hs@nabladev.com>
> >> Cc: Michal Simek <michal.simek@amd.com>
> >> Cc: Sughosh Ganu <sughosh.ganu@arm.com>
> >> Cc: Antony Kurniawan Soemardi <linux@smankusors.com>
> >> Cc: Luca Weiss <luca.weiss@fairphone.com>
> >> Cc: Balaji Selvanathan <balaji.selvanathan@oss.qualcomm.com>
> >>
> >> ---
> >> Casey Connolly (15):
> >>       Revert "dm: SMEM (Shared memory) uclass"
> >>       smem: drop drivers/smem
> >>       Revert "test: smem: add basic smem test"
> >>       Revert "drivers: smem: sandbox"
> >>       mach-snapdragon: fix reserved memory carveout
> >>       soc: qcom: import smem from Linux 6.11-rc2
> >>       soc: qcom: smem: adjust headers for U-Boot
> >>       soc: qcom: smem: adjust for U-Boot
> >>       soc: qcom: smem: get serial number from socinfo
> >>       soc: qcom: smem: stub functions
> >>       soc: qcom: smem: add build infra
> >>       mach-snapdragon: move memory parsing to its own file
> >>       mach-snapdragon: support parsing memory map from SMEM
> >>       mach-snapdragon: fetch serial# from SMEM
> >>       configs: add qcom_sm8650_defconfig and debug fragment
> >>
> >>  MAINTAINERS                                  |   1 -
> >>  arch/arm/Kconfig                             |   3 +-
> >>  arch/arm/mach-snapdragon/Makefile            |   2 +-
> >>  arch/arm/mach-snapdragon/board.c             | 253 ++++-----
> >>  arch/arm/mach-snapdragon/dram.c              | 239 ++++++++
> >>  arch/arm/mach-snapdragon/qcom-priv.h         |  17 +
> >>  arch/arm/mach-snapdragon/rampart.h           | 194 +++++++
> >>  arch/sandbox/dts/test.dts                    |   4 -
> >>  board/qualcomm/debug-sm8650.config           |   5 +
> >>  configs/qcom_sm8650_defconfig                |  16 +
> >>  configs/sandbox64_defconfig                  |   2 -
> >>  configs/sandbox_defconfig                    |   2 -
> >>  drivers/Kconfig                              |   2 -
> >>  drivers/Makefile                             |   1 -
> >>  drivers/smem/Kconfig                         |  25 -
> >>  drivers/smem/Makefile                        |   7 -
> >>  drivers/smem/sandbox_smem.c                  |  44 --
> >>  drivers/smem/smem-uclass.c                   |  46 --
> >>  drivers/soc/qcom/Kconfig                     |   8 +
> >>  drivers/soc/qcom/Makefile                    |   1 +
> >>  drivers/{smem/msm_smem.c => soc/qcom/smem.c} | 777 ++++++++++++++++-----------
> >>  include/dm/uclass-id.h                       |   1 -
> >>  include/smem.h                               |  90 ----
> >>  include/soc/qcom/smem.h                      |  36 ++
> >>  include/soc/qcom/socinfo.h                   | 111 ++++
> >>  test/dm/Makefile                             |   1 -
> >>  test/dm/smem.c                               |  26 -
> >>  27 files changed, 1186 insertions(+), 728 deletions(-)
> >> ---
> >> base-commit: 2920b49fb117dd70b6219804bf0d298c96f184f2
> >>
> >> // Casey (she/they)
> >>
> 
> -- 
> // Casey (she/her)
>