Hi Nabih,

Thank you for your review and comments. I will wait a few more days
to see if there is additional feedback from others. If you encounter
anything unexpected in your local environment, please let me know. I
will try to address it in the v4 patch if possible.

Best regards,
Kane
> -----Original Message-----
> From: Nabih Estefan <nabihestefan@google.com>
> Sent: Thursday, December 11, 2025 7:02 AM
> To: Kane Chen <kane_chen@aspeedtech.com>
> Cc: Cédric Le Goater <clg@kaod.org>; Peter Maydell
> <peter.maydell@linaro.org>; Steven Lee <steven_lee@aspeedtech.com>; Troy
> Lee <leetroy@gmail.com>; Jamin Lin <jamin_lin@aspeedtech.com>; Andrew
> Jeffery <andrew@codeconstruct.com.au>; Joel Stanley <joel@jms.id.au>;
> open list:ASPEED BMCs <qemu-arm@nongnu.org>; open list:All patches CC
> here <qemu-devel@nongnu.org>; Troy Lee <troy_lee@aspeedtech.com>
> Subject: Re: [PATCH v3 00/18] hw/arm/aspeed: AST1700 LTPI support and
> device hookups
> 
> On Sun, Dec 7, 2025 at 11:45 PM Kane Chen via <qemu-devel@nongnu.org>
> wrote:
> >
> > From: Kane-Chen-AS <kane_chen@aspeedtech.com>
> >
> > Hi all,
> >
> > LTPI (LVDS Tunneling Protocol & Interface) is defined in the OCP
> > DC-SCM
> > 2.0 specification (see Figure 2):
> > https://www.opencompute.org/documents/ocp-dc-scm-2-0-ltpi-ver-1-0-pdf
> >
> > LTPI provides a protocol and physical interface for tunneling various
> > low-speed signals between the Host Processor Module (HPM) and the
> > Satellite Controller Module (SCM). In Figure 2 of the specification,
> > the AST27x0 SoC (left) integrates two LTPI controllers, allowing it to
> > connect to up to two AST1700 boards. On the other side, the AST1700
> > consolidates HPM FPGA functions and multiple peripheral interfaces
> > (GPIO, UART, I2C, I3C, etc.) onto a single board.
> >
> > Because the AST1700 exposes additional I/O interfaces (GPIO, I2C, I3C,
> > and others), it acts as an I/O expander. Once connected over LTPI, the
> > AST27x0 can control additional downstream devices through this link.
> >
> > This patch series is based on the SGPIO changes:
> > https://lore.kernel.org/qemu-devel/20251106-aspeed-sgpio-v1-0-b0260937
> > 16fa@google.com/
> >
> > It introduces a basic LTPI controller model and wires it into the
> > AST27x0 SoC. The series also adds the AST1700-specific LTPI expander
> > device and incrementally connects common peripherals on the AST1700
> > model. For the I3C block, which may cause kernel crashes, its MMIO
> > region is modeled as an unimplemented device to reserve address space
> > and make the missing functionality explicit, ensuring stable guest
> > probing.
> >
> > In the official release images, the AST1700 functions are not included
> > by default. To test the AST1700-related functionality, please include
> > the following DTS files for probing:
> >
> https://github.com/AspeedTech-BMC/linux/blob/aspeed-master-v6.6/arch/a
> > rm64/boot/dts/aspeed/aspeed-ltpi0.dtsi
> >
> https://github.com/AspeedTech-BMC/linux/blob/aspeed-master-v6.6/arch/a
> > rm64/boot/dts/aspeed/aspeed-ltpi1.dtsi
> >
> > After including these DTS files in the BMC image, you can verify LTPI
> > functionality using the following scenarios:
> >
> > 1. In U-Boot:
> >    Run the ltpi command to trigger the LTPI connection and display the
> >    current connection status.
> > 2. In BMC Linux:
> >    Run i2cdetect -y <16-38> to scan and test the I2C buses exposed by
> >    the AST1700.
> >
> > Any feedback or suggestions are appreciated!
> >
> > Kane
> >
> 
> I left some nit-picky notes on some of the patches, but after fixing patch 03
> everything else seems good. FWIW I brought the whole patchset into our
> branch and not only does everything compile properly, but I can also see and
> interact with the i2c buses from the AST1700 in our internal platforms. Will
> wait for v4 to add the reviewed and tested tags, but LGTM!
> 
> > ---
> >
> > ChangeLog
> > ---------
> > v3:
> > - Add PWM model
> > - Integrate the SGPIO model
> > - Fix I2C test case failure
> > - Refine code structure
> >
> > v2:
> > - Separate the AST1700 model into a standalone implementation
> > - Refine the mechanism for assigning the AST1700 board number
> >
> > v1:
> > - Initial version
> > ---
> >
> > Kane-Chen-AS (18):
> >   hw/misc: Add LTPI controller
> >   hw/arm/aspeed: Attach LTPI controller to AST27X0 platform
> >   hw/misc: Add basic Aspeed PWM model
> >   hw/arm/aspeed: Add AST1700 LTPI expander device model
> >   hw/arm/aspeed: Integrate AST1700 device into AST27X0
> >   hw/arm/aspeed: Integrate interrupt controller for AST1700
> >   hw/arm/aspeed: Attach LTPI controller to AST1700 model
> >   hw/arm/aspeed: Attach UART device to AST1700 model
> >   hw/arm/aspeed: Attach SRAM device to AST1700 model
> >   hw/arm/aspeed: Attach SPI device to AST1700 model
> >   hw/arm/aspeed: Attach ADC device to AST1700 model
> >   hw/arm/aspeed: Attach SCU device to AST1700 model
> >   hw/arm/aspeed: Attach GPIO device to AST1700 model
> >   hw/arm/aspeed: attach I2C device to AST1700 model
> >   hw/arm/aspeed: Attach WDT device to AST1700 model
> >   hw/arm/aspeed: Attach PWM device to AST1700 model
> >   hw/arm/aspeed: Attach SGPIOM device to AST1700 model
> >   hw/arm/aspeed: Model AST1700 I3C block as unimplemented device
> >
> >  include/hw/arm/aspeed_ast1700.h |  53 +++++++
> >  include/hw/arm/aspeed_soc.h     |  25 ++-
> >  include/hw/i2c/aspeed_i2c.h     |   1 +
> >  include/hw/intc/aspeed_intc.h   |   2 +
> >  include/hw/misc/aspeed_ltpi.h   |  32 ++++
> >  include/hw/misc/aspeed_pwm.h    |  31 ++++
> >  hw/arm/aspeed_ast1700.c         | 269
> ++++++++++++++++++++++++++++++++
> >  hw/arm/aspeed_ast27x0.c         | 163 +++++++++++++++++--
> >  hw/i2c/aspeed_i2c.c             |  19 ++-
> >  hw/intc/aspeed_intc.c           |  60 +++++++
> >  hw/misc/aspeed_ltpi.c           | 194 +++++++++++++++++++++++
> >  hw/misc/aspeed_pwm.c            | 121 ++++++++++++++
> >  hw/arm/meson.build              |   1 +
> >  hw/misc/meson.build             |   2 +
> >  hw/misc/trace-events            |   4 +
> >  15 files changed, 957 insertions(+), 20 deletions(-)  create mode
> > 100644 include/hw/arm/aspeed_ast1700.h  create mode 100644
> > include/hw/misc/aspeed_ltpi.h  create mode 100644
> > include/hw/misc/aspeed_pwm.h  create mode 100644
> > hw/arm/aspeed_ast1700.c  create mode 100644 hw/misc/aspeed_ltpi.c
> > create mode 100644 hw/misc/aspeed_pwm.c
> >
> > --
> > 2.43.0
> >
> >