[U-Boot] [PATCH v1 00/20] Enable ARM Trusted Firmware for U-Boot

Ang, Chee Hong chee.hong.ang at intel.com
Tue Dec 3 02:37:01 CET 2019


> Am 02.12.2019 um 17:10 schrieb Ang, Chee Hong:
> >> On Mon, Dec 2, 2019 at 4:18 PM Ang, Chee Hong
> >> <chee.hong.ang at intel.com>
> >> wrote:
> >>>
> >>>> On Mon, Dec 2, 2019 at 3:08 PM Ang, Chee Hong
> >>>> <chee.hong.ang at intel.com>
> >>>> wrote:
> >>>>>
> >>>>>> On Mon, Dec 2, 2019 at 2:38 PM Ang, Chee Hong
> >>>>>> <chee.hong.ang at intel.com>
> >>>>>> wrote:
> >>>>>>>
> >>>>>>>> On Mon, Dec 2, 2019 at 11:25 AM <chee.hong.ang at intel.com>
> >> wrote:
> >>>>>>>>>
> >>>>>>>>> From: "Ang, Chee Hong" <chee.hong.ang at intel.com>
> >>>>>>>>>
> >>>>>>>>> New U-boot flow with ARM Trusted Firmware (ATF) support:
> >>>>>>>>> SPL (EL3) -> ATF-BL31 (EL3) -> U-Boot Proper (EL2) -> Linux
> >>>>>>>>> (EL1)
> >>>>>>>>
> >>>>>>>> Adding support for ATF means that using U-Boot on Stratix10 and
> >>>>>>>> Agilex without ATF keeps working, right?
> >>>>>>> ATF is needed in order for Stratix10 and Agilex's U-Boot to work.
> >>>>>>
> >>>>>> Is there a technical requirement for that?
> >>>>> Yes. We are using ATF to provide PSCI services such as system
> >>>>> reset (COLD reset), CPU_ON/CPU_OFF (CPU hotplug in Linux) and
> >>>>> other secure services such as mailbox communications with Secure
> >>>>> Device Manager and accessing the System Manager registers which
> >>>>> are
> >> secure.
> >>>>> Without PSCI services, we are able to boot until U-Boot proper only.
> >>>>> Currently, our U-Boot in mainline doesn't boot to Linux due to
> >>>>> these missing
> >>>> PSCI services.
> >>>>> Another reason is we have another boot flow which is using ATF + UEFI.
> >>>>> So now we are re-using the PSCI services from ATF so that now
> >>>>> U-Boot and UEFI share the same ATF-BL31 image so that we don't
> >>>>> have to
> >>>> reimplement another sets of PSCI services for U-Boot again.
> >>>>> This will greatly reduce our engineering efforts.
> >>>>
> >>>> Hmm, thanks for the explanation.
> >>>>
> >>>> I don't really think I can review this, given the lack of knowledge
> >>>> about that PSCI stuff.
> >>> I believe you can review it.
> >>> Have you briefly gone through the patches ? It has nothing to do
> >>> with the PSCI
> >> stuff.
> >>> It just call the invoke_smc() function to call the ATF's PSCI
> >>> functions. Those PSCI functions in ATF will do the rest.
> >>
> >> No, not yet. But see below.
> >>
> >>>>
> >>>> I must say it seems strange to me that U-Boot would have to rely on
> >>>> ATF
> >> though.
> >>>> How do other platforms implement this? Shouldn't PSCI be generic or
> >>>> is it really platform specific? If it's generic, isn't that a
> >>>> dupliation of code if you implement e.g. a reset driver for
> >>>> Stratix10 but call
> >> into PSCI?
> >>> It's not strange at all.  A lot of U-Boot users already using this
> >>> boot flow (ATF +
> >> U-Boot).
> >>
> >> Just because other boards do this doesn't mean it's not strange.
> >> Wasn't there some kind of discussion around that PSCI stuff to make it
> available from U-Boot?
> >> What's wrong with that way?
> > Our downstream U-Boot branch is already implemented the PSCI stuffs in U-
> Boot.
> > I tried to upstream my PSCI code:
> > https://lists.denx.de/pipermail/u-boot/2019-May/368822.html
> >
> > Marek pointed me to this thread:
> > https://www.mail-archive.com/u-boot@lists.denx.de/msg319458.html
> >
> > He had a point. He suggested maybe we can implement the PSCI stuffs in
> > SPL/TPL. I took a look at the U-Boot code and found out ATF is already well
> supported. Why don't we just use the PSCI code from ATF rather than re-
> implementing the PSCI code again in SPL/TPL.
> > It will save our effort to maintain two PSCI code in U-Boot and ATF while we
> already have the ATF PSCI implementation to support UEFI.
> 
> It seems to me we do have working code in U-Boot, what's missing is "only" to
> turn it ino PSCI?
Existing PSCI framework in U-Boot provide a way for us to turn the code into a PSCI handler
by just adding a '__secure' keyword before the function name. See:
https://gitlab.denx.de/u-boot/u-boot/blob/master/arch/arm/mach-socfpga/mailbox_s10.c

Below is one of the functions that has 2 versions. One 'live' in a normal code section and another
one will be relocated to "__secure" section (for PSCI). You can see that 2 same functions
are duplicated for normal code section and PSCI section.

int mbox_send_cmd(u8 id, u32 cmd, u8 is_indirect, u32 len, u32 *arg,
		  u8 urgent, u32 *resp_buf_len, u32 *resp_buf)
{
	return mbox_send_cmd_common(id, cmd, is_indirect, len, arg, urgent,
			       resp_buf_len, resp_buf);
}

int __secure mbox_send_cmd_psci(u8 id, u32 cmd, u8 is_indirect, u32 len,
				u32 *arg, u8 urgent, u32 *resp_buf_len,
				u32 *resp_buf)
{
	return mbox_send_cmd_common(id, cmd, is_indirect, len, arg, urgent,
			       resp_buf_len, resp_buf);
}

Those functions that are needed by PSCI runtime need to be duplicated for "__secure" section.
U-Boot Proper will copy and relocate the PSCI code in "__secure" section to a location before booting
Linux whereby they can be called by Linux. Using the PSCI framework, U-Boot proper is not able to call
any PSCI functions because PSCI code is not available until U-Boot proper ready to boot Linux.
So that's the reason we need to have 2 sets of code in U-Boot. One for SPL/U-Boot and another one for
PSCI section which is used by Linux.
Currently we have 2 implementations for FPGA reconfiguration driver in our downstream branch.
One for SPL/U-Boot and another one for Linux (PSCI). FPGA reconfiguration driver for U-Boot is already
upstreamed but I don't think I can get the FPGA reconfiguration for the PSCI part upstreamed.
They are 2 sets of different code for the same purpose. But that is what we have done in downstream
to make sure we can support Linux.

BTW, we are going to get rid of those duplicated code for PSCI after we switch to ATF boot flow.
> 
> And given U-Boot aims to support UEFI (kind of?), I'd rather argue: why do you
> need ATF at all?

No, U-Boot does not aim to support UEFI. We have 2 boot flows that don't mix:

1) U-Boot -> ATF-BL31 -> U-Boot Proper -> Linux

2) ATF-BL2 -> ATF-BL31 -> UEFI -> Other OSes or Linux

These two boot flows now share the same code base (ATF-BL31).
> 
> Indeed, having the same code in both seems like double effort for maintenance.
> 
> >>
> >> In my opinion, you're reducing functionality in U-Boot by making ATF
> >> a requirement.
> >>
> >> And by saying "I can't review this", I mean this looks like a
> >> questionable way to me and I'm not the one to say if a U-Boot board should
> go this way or not.
> > I understand. Btw, who should I include to review this ?
> >>
> >>> Yes. PSCI is a generic software interface which encapsulate the
> >>> platform
> >> specific code.
> >>> Let me give you a good example in one of your sysreset driver you
> >>> have
> >> implemented for S10.
> >>>
> >>> #include <dm.h>
> >>> #include <errno.h>
> >>> #include <sysreset.h>
> >>> -#include <asm/arch/mailbox_s10.h>
> >>>
> >>>   static int socfpga_sysreset_request(struct udevice *dev,
> >>>                                      enum sysreset_t type)  {
> >>>   -      puts("Mailbox: Issuing mailbox cmd REBOOT_HPS\n");
> >>>   -      mbox_reset_cold();
> >>>   +      psci_system_reset();
> 
> And coming back on this, the sysreset driver won't work in SPL any more, right?
You brought a very good point. See my comment at the bottom.
> 
> >>
> >> So this is not an socfgpa_s10 specific driver any more, right?
This driver code can be renamed to more generic name such as socfpga_soc64.c.
So that it can be shared by both Stratix10 and Agilex.
> >>
> >>>          return -EINPROGRESS;
> >>>   }
> >>>
> >>> Above is the changes in one of my patchsets, the sysreset driver for
> >>> S10 used to call mbox_reset_cold() to send mailbox message to Secure
> >>> Device Manager
> >>> (SDM) to trigger COLD reset.
> >>> Calling 'mbox_reset_cold()' means you are calling platform specific
> >>> code in the sysreset driver to perform COLD reset. What if method to
> >>> trigger
> >> COLD reset is changed in new platform ?
> >>> We have to change the sysreset driver code to support another new
> platform.
> >>> If this function call is replaced with "psci_system_reset()", we
> >>> don't have to change the code at all because all the platform
> >>> specific code for COLD reset is now reside in ATF because this
> >>> function just invoke the PSCI function provided by ATF. You just
> >>> have to replace the ATF binary with the new implementation for the
> >>> new platform. We can re-use this sysreset driver for any platform
> >>> that support ATF. In fact, it makes our U-Boot driver code more
> >>> 'generic' because PSCI interface stay the same. BTW, Linux also call
> >>> PSCI functions to perform COLD reset. By
> >> using ATF, U-Boot and Linux share the same COLD reset service provided by
> ATF.
> >> It actually reduce code duplication.
> >>
> >> What I meant was code duplication inside the U-Boot tree (having one
> >> driver for each arch but in effect all those drivers will call into the same psci
> function).
> > Can different archs share the same driver if the driver code is common to
> those platforms ?
> 
> I don't know why not. However, you then need a different way to select this
> driver: you clearly cannot use DT compatibles as this DT entry does not in any
> way stand for what you make the driver binding to it execute.
> 
> Instead, I would think of a way to make your PSCI-aware U-Boot proper use a
> generic PSCI-reset driver instead of the one matching the devicetree. And then
> keep in mind you still need the DT-matching driver in SPL. Thinking about it,
> having a driver in SPL you don't use in U-Boot proper is probably not done, yet,
> as well.
I don't have any problem with this approach (PSCI-reset driver) but it is very easy to support SPL and U-Boot proper
in the same driver by just checking the current exception level. Please take a look at the code below.

#include <dm.h>
#include <errno.h>
#include <sysreset.h>
#include <asm/arch/mailbox_s10.h>

static int socfpga_sysreset_request(struct udevice *dev,
                                     enum sysreset_t type)  {
-      puts("Mailbox: Issuing mailbox cmd REBOOT_HPS\n");
+      If (current_el() == 3)
+                mbox_reset_cold();
+      else
+                psci_system_reset();
        return -EINPROGRESS;
}

We can make the sysreset driver compatible in SPL and U-Boot proper by just checking the current exception level.
If it's EL3 (secure), we knew SPL is running and otherwise U-Boot proper (EL2, non-secure) is running.
Or we can make a small generic function like below and call it from sysreset driver code:

void soc64_cold_reset(void)
{
      If (current_el() == 3)
                mbox_reset_cold();
      else
                psci_system_reset();
}

> 
> >
> >> What you're doing is to move this code from U-Boot open U-Boot
> >> sources to possibly closed source ATF sources. But we've already had
> >> that discussion, I think...
> > Our PSCI implementation in ATF is open source:
> > https://github.com/ARM-software/arm-trusted-firmware/tree/master/plat/
> > intel/soc
> 
> Well, open source... Without implying anything: it's BSD, so it's open source as
> long as Intel wants it to be open source and nothing prevents the next manager
> from keeping additions or even bugfixes closed source.
> For whatever reasons might come.
> 
> 
> Regards,
> Simon
> 
> >
> >>
> >> Regards,
> >> Simon
> >>
> >>>
> >>> I think you are aware of we are working to move the mailbox driver
> >>> code away
> >> from arch to drivers.
> >>> You will see that a lot of those mailbox functions will be removed
> >>> from the
> >> mailbox driver.
> >>> One of them is 'mbox_reset_cold()' which you called in sysreset driver for
> S10.
> >>>
> >>>> Regards,
> >>>> Simon
> >>>>
> >>>>>>
> >>>>>> Regard,
> >>>>>> Simon
> >>>>>>
> >>>>>>>>>
> >>>>>>>>> SPL loads the u-boot.itb which consist of:
> >>>>>>>>> 1) u-boot-nodtb.bin (U-Boot Proper image)
> >>>>>>>>> 2) u-boot.dtb (U-Boot Proper DTB)
> >>>>>>>>> 3) bl31.bin (ATF-BL31 image)
> >>>>>>>>>
> >>>>>>>>> Supported Platform: Intel SoCFPGA 64bits (Stratix10 &
> >>>>>>>>> Agilex)
> >>>>>>>>>
> >>>>>>>>> Now, U-Boot Proper is running in non-secure mode (EL2), it
> >>>>>>>>> invokes SMC/PSCI calls provided by ATF to perform COLD reset,
> >>>>>>>>> System Manager register accesses and mailbox communications
> >>>>>>>>> with Secure Device Manager (SDM).
> >>>>>>>>>
> >>>>>>>>> Steps to build the U-Boot with ATF support:
> >>>>>>>>> 1) Build U-Boot
> >>>>>>>>> 2) Build ATF BL31
> >>>>>>>>> 3) Copy ATF BL31 binary image into U-Boot's root folder
> >>>>>>>>> 4) "make u-boot.itb" to generate u-boot.itb
> >>>>>>>>>
> >>>>>>>>> These patchsets have dependency on:
> >>>>>>>>> [U-Boot,v8,00/19] Add Intel Agilex SoC support:
> >>>>>>>>> https://patchwork.ozlabs.org/cover/1201373/
> >>>>>>>>>
> >>>>>>>>> Chee Hong Ang (19):
> >>>>>>>>>    arm: socfpga: add fit source file for pack itb with ATF
> >>>>>>>>>    arm: socfpga: Add function for checking description from
> >>>>>>>>> FIT
> >> image
> >>>>>>>>>    arm: socfpga: Load FIT image with ATF support
> >>>>>>>>>    arm: socfpga: Override 'lowlevel_init' to support ATF
> >>>>>>>>>    configs: socfpga: Enable FIT image loading with ATF support
> >>>>>>>>>    arm: socfpga: Disable "spin-table" method for booting Linux
> >>>>>>>>>    arm: socfpga: Add SMC helper function for Intel SOCFPGA (64bits)
> >>>>>>>>>    arm: socfpga: Define SMC function identifiers for PSCI SiP services
> >>>>>>>>>    arm: socfpga: Add secure register access helper functions for SoC
> >>>>>>>>>      64bits
> >>>>>>>>>    arm: socfpga: Secure register access for clock manager (SoC 64bits)
> >>>>>>>>>    arm: socfpga: Secure register access in PHY mode setup
> >>>>>>>>>    arm: socfpga: Secure register access for reading PLL frequency
> >>>>>>>>>    mmc: dwmmc: socfpga: Secure register access in MMC driver
> >>>>>>>>>    net: designware: socfpga: Secure register access in MAC driver
> >>>>>>>>>    arm: socfpga: Secure register access in Reset Manager driver
> >>>>>>>>>    arm: socfpga: stratix10: Initialize timer in SPL
> >>>>>>>>>    arm: socfpga: stratix10: Refactor FPGA reconfig driver to
> >>>>>>>>> support
> >> ATF
> >>>>>>>>>    arm: socfpga: Bridge reset now invokes SMC calls to query
> >>>>>>>>> FPGA
> >>>> config
> >>>>>>>>>      status
> >>>>>>>>>    sysreset: socfpga: Invoke PSCI call for COLD reset
> >>>>>>>>>
> >>>>>>>>> Dalon Westergreen (1):
> >>>>>>>>>    configs: stratix10: Remove CONFIG_OF_EMBED
> >>>>>>>>
> >>>>>>>> This one is included in another series already:
> >>>>>>>> https://patchwork.ozlabs.org/user/todo/uboot/?series=132976
> >>>>>>>>
> >>>>>>>> Does this mean that one will be abandonen?
> >>>>>>>> So the combined hex output part of that series is not required
> >>>>>>>> any
> >> more?
> >>>>>>>>
> >>>>>>>> Regards,
> >>>>>>>> Simon
> >>>>>>>>
> >>>>>>>>>
> >>>>>>>>>   arch/arm/mach-socfpga/Kconfig                      |   2 -
> >>>>>>>>>   arch/arm/mach-socfpga/Makefile                     |   4 +
> >>>>>>>>>   arch/arm/mach-socfpga/board.c                      |  10 +
> >>>>>>>>>   arch/arm/mach-socfpga/clock_manager_agilex.c       |   5 +-
> >>>>>>>>>   arch/arm/mach-socfpga/clock_manager_s10.c          |   5 +-
> >>>>>>>>>   arch/arm/mach-socfpga/include/mach/misc.h          |   3 +
> >>>>>>>>>   .../mach-socfpga/include/mach/secure_reg_helper.h  |  20 ++
> >>>>>>>>>   arch/arm/mach-socfpga/lowlevel_init.S              |  48 +++
> >>>>>>>>>   arch/arm/mach-socfpga/misc_s10.c                   |  47 ++-
> >>>>>>>>>   arch/arm/mach-socfpga/reset_manager_s10.c          |  31 +-
> >>>>>>>>>   arch/arm/mach-socfpga/secure_reg_helper.c          |  67 ++++
> >>>>>>>>>   arch/arm/mach-socfpga/timer_s10.c                  |   3 +-
> >>>>>>>>>   arch/arm/mach-socfpga/wrap_pll_config_s10.c        |   9 +-
> >>>>>>>>>   board/altera/soc64/its/fit_spl_atf.its             |  51 +++
> >>>>>>>>>   configs/socfpga_agilex_defconfig                   |   8 +-
> >>>>>>>>>   configs/socfpga_stratix10_defconfig                |   9 +-
> >>>>>>>>>   drivers/fpga/stratix10.c                           | 261 ++++----------
> >>>>>>>>>   drivers/mmc/socfpga_dw_mmc.c                       |   7 +-
> >>>>>>>>>   drivers/net/dwmac_socfpga.c                        |   5 +-
> >>>>>>>>>   drivers/sysreset/sysreset_socfpga_s10.c            |   4 +-
> >>>>>>>>>   include/configs/socfpga_soc64_common.h             |   2 +-
> >>>>>>>>>   include/linux/intel-smc.h                          | 374
> >> +++++++++++++++++++++
> >>>>>>>>>   22 files changed, 732 insertions(+), 243 deletions(-) create
> >>>>>>>>> mode
> >>>>>>>>> 100644
> >>>>>>>>> arch/arm/mach-socfpga/include/mach/secure_reg_helper.h
> >>>>>>>>>   create mode 100644 arch/arm/mach-socfpga/lowlevel_init.S
> >>>>>>>>>   create mode 100644
> >>>>>>>>> arch/arm/mach-socfpga/secure_reg_helper.c
> >>>>>>>>>   create mode 100644 board/altera/soc64/its/fit_spl_atf.its
> >>>>>>>>>   create mode 100644 include/linux/intel-smc.h
> >>>>>>>>>
> >>>>>>>>> --
> >>>>>>>>> 2.7.4
> >>>>>>>>>



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