Re: [RFC PATCH 00/11] soc: mediatek: add a DRAM ECC error handling driver

[Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>]

On Mon, 2 Nov 2026 12:36:42 -0800
Jonathan Cameron <jonathan.cameron@oss.qualcomm.com> wrote:

> On Mon, 2 Nov 2026 17:23:22 +0800
> santino.wang <santino.wang@mediatek.com> wrote:
> 

+CC Mauro as well as I realized I asked about userspace part and
he may have input on that as well as on the kernel side of things.

> > From: Santino Wang <santino.wang@mediatek.com>
> > 
> > On the MediaTek mt8992 SoC the DRAM controller (DRAMC) raises an interrupt for
> > every corrected (CE) and uncorrectable (UCE) ECC error. The interrupt is
> > owned by the secure firmware (Arm Trusted Firmware at EL3). It reads the
> > DRAMC error registers, applies the error containment policy and the CE
> > storm protection, and hands the error to the OS firmware-first as an ACPI
> > GHES record in a buffer that UEFI describes in the HEST. The OS is
> > notified with an edge interrupt that the DSDT delivers through a Generic
> > Event Device and a Hardware Error Device (GSIV notification).  
> 
> So far this all sounds standard for asynchronous error reporting.
> I'm assuming you have a something else for synchronous consumption.
> From a Linux side of things we just care that error record shows up
> and is signaled via GSIV (with normal Generic Event Device and Hardware
> Error Device in the DSDT I guess)
> 
> > 
> > The record carries a standard Platform Memory Error section and a
> > MediaTek vendor section with the raw DRAMC error registers.  
> 
> I'd like some details here on what those raw registers are bringing
> to the OS wrt to handling these errors. 
> 
> What extra info?  I see you have a subchannel in there, but Memory
> Error Section 2 brings that.  So why isn't this being reported
> as a standard CPER?
> 
> > This series
> > adds the driver that consumes the vendor section through the existing
> > ghes_register_vendor_record_notifier() interface. No change to the GHES
> > core or to arm64 code is needed.  
> 
> Given a lot here doesn't sound mediatek specific it feels like it
> shouldn't necessarily be in the vendor defined path.  More discussion
> of why you have gone that way would be help.
> 
> > 
> > The driver
> >  - decodes the most severe error of a record and keeps counters, also
> >    across boots in EFI variables,  
> 
> Interesting.  How does this compare with just making it a userspace problem?
> Perhaps you can't do that for some reason but it would take a lot to
> convince me that it makes sense to have an upstream solution that relies
> on custom EFI variable path.
> 
> >  - isolates pages with memory_failure(): immediately for a recoverable
> >    UCE on memory that Linux manages, and for a page whose corrected
> >    error count reaches a threshold (leaky bucket); memory owned by a
> >    device is only reported to its owner,  
> 
> This sounds standard, so I'm missing why you need a vendor driver for it.
> Please provides some more info.
> 
> >  - lets in-kernel clients and user space (generic netlink, tracepoints)
> >    follow the events,  
> 
> Why your own netlink for this?  These are memory errors so I'd expect
> existing paths to be sufficient, or perhaps there to be a need to
> extend those as Pierre is doing with the Memory Error Section 2 series.
> 
> >  - exposes the containment policy, the storm protection and per range
> >    severity overrides in sysfs and pushes them to the secure firmware
> >    through a vendor SMC call,  
> 
> The pushing of policy down to firmware is possibly something that needs
> a custom driver.  I need to think a bit more on that and check a few things.
> Input from Borislav or Tony might help here.
> 
> >  - after a fatal UCE (GHES panic and reset), finds the error in the BERT
> >    of the next boot and reports it through the mc_event tracepoint.  
> 
> If this were using the standard records that should just work. What
> is missing that you need?
> 
> > 
> > The driver depends on firmware that is not part of this series: the
> > secure firmware provides the SMC interface used by patch 2 and writes the
> > vendor section decoded by patch 4. The firmware side (the TF-A and
> > edk2-platforms changes for the mt8992 SoC, plus the preloader that keeps
> > the error across the reset) is being developed in the vendor's BSP trees
> > and is not published yet.
> > 
> > Open question for this RFC: is drivers/soc/mediatek the right place for a
> > driver that is built on GHES vendor records and a vendor SMC interface, or
> > would the maintainers prefer another location?  
> 
> You already got a reply on that. Almost nothing should ever go in drivers/soc
> and definitely not something RAS related. +CC linux-edac, Borislav and Tony.
> 
> Anyhow, always interesting to discuss expanding what we do for
> memory error handling, so I'll be interested to see what other feedback
> this series gets.
> 
> Thanks,
> 
> Jonathan
> 
> > 
> > Testing: each patch builds with the arm64 defconfig plus
> > CONFIG_MTK_DRAM_ECC=m on linux-next 20261030 (W=1, no warnings).
> > The series has been tested pre-silicon on a Palladium emulation platform.
> > 
> > Santino Wang (11):
> >   soc: mediatek: dram-ecc: add the DRAM ECC driver skeleton
> >   soc: mediatek: dram-ecc: add the SMC interface to the secure firmware
> >   soc: mediatek: dram-ecc: add tracepoints
> >   soc: mediatek: dram-ecc: handle GHES vendor records from the firmware
> >   soc: mediatek: dram-ecc: add error counters and the address lists
> >   soc: mediatek: dram-ecc: keep error counters across boots
> >   soc: mediatek: dram-ecc: add containment policy and storm protection
> >   soc: mediatek: dram-ecc: add the corrected error leaky bucket
> >   soc: mediatek: dram-ecc: add a generic netlink event interface
> >   soc: mediatek: dram-ecc: report an uncorrectable error of the previous
> >     boot
> >   Documentation: ABI: add the sysfs attributes of the MediaTek DRAM ECC
> >     driver
> > 
> >  .../ABI/testing/sysfs-class-mtk-dram-ecc      | 182 +++++++++
> >  MAINTAINERS                                   |  10 +
> >  drivers/soc/mediatek/Kconfig                  |   2 +
> >  drivers/soc/mediatek/Makefile                 |   1 +
> >  drivers/soc/mediatek/dram-ecc/Kconfig         |  19 +
> >  drivers/soc/mediatek/dram-ecc/Makefile        |   3 +
> >  drivers/soc/mediatek/dram-ecc/core/Makefile   |  20 +
> >  .../soc/mediatek/dram-ecc/core/addresses.c    |  88 ++++
> >  .../soc/mediatek/dram-ecc/core/addresses.h    |  13 +
> >  .../soc/mediatek/dram-ecc/core/bert_check.c   | 240 +++++++++++
> >  .../soc/mediatek/dram-ecc/core/bert_check.h   |  12 +
> >  drivers/soc/mediatek/dram-ecc/core/counters.c | 336 ++++++++++++++++
> >  drivers/soc/mediatek/dram-ecc/core/counters.h |  29 ++
> >  .../mediatek/dram-ecc/core/ghes_notifier.c    | 377 ++++++++++++++++++
> >  .../mediatek/dram-ecc/core/ghes_notifier.h    |  22 +
> >  drivers/soc/mediatek/dram-ecc/core/main.c     | 113 ++++++
> >  .../soc/mediatek/dram-ecc/core/mtk_dram_ecc.h |  27 ++
> >  .../dram-ecc/core/mtk_dram_ecc_event.h        |  47 +++
> >  drivers/soc/mediatek/dram-ecc/core/netlink.c  |  83 ++++
> >  drivers/soc/mediatek/dram-ecc/core/netlink.h  |  14 +
> >  .../dram-ecc/core/policy/address_range.c      | 120 ++++++
> >  .../dram-ecc/core/policy/containment.c        | 107 +++++
> >  .../dram-ecc/core/policy/leaky_bucket.c       | 277 +++++++++++++
> >  .../mediatek/dram-ecc/core/policy/policy.c    |  57 +++
> >  .../mediatek/dram-ecc/core/policy/policy.h    |  23 ++
> >  .../dram-ecc/core/policy/storm_protection.c   | 137 +++++++
> >  drivers/soc/mediatek/dram-ecc/core/smc.c      | 137 +++++++
> >  drivers/soc/mediatek/dram-ecc/core/smc.h      |  55 +++
> >  drivers/soc/mediatek/dram-ecc/core/trace.c    |   6 +
> >  drivers/soc/mediatek/dram-ecc/core/trace.h    | 119 ++++++
> >  include/uapi/linux/mtk_dram_ecc_netlink.h     |  44 ++
> >  31 files changed, 2720 insertions(+)
> >  create mode 100644 Documentation/ABI/testing/sysfs-class-mtk-dram-ecc
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/Kconfig
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/Makefile
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/Makefile
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/addresses.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/addresses.h
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/bert_check.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/bert_check.h
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/counters.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/counters.h
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/ghes_notifier.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/ghes_notifier.h
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/main.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/mtk_dram_ecc.h
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/mtk_dram_ecc_event.h
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/netlink.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/netlink.h
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/policy/address_range.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/policy/containment.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/policy/leaky_bucket.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/policy/policy.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/policy/policy.h
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/policy/storm_protection.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/smc.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/smc.h
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/trace.c
> >  create mode 100644 drivers/soc/mediatek/dram-ecc/core/trace.h
> >  create mode 100644 include/uapi/linux/mtk_dram_ecc_netlink.h
> >   
>