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Hifive Premier P550[1] is a Mini-DTX form factor board with EIC7700X.
It has a STM32F407VET6 onboard MCU acting as the BMC, controlling
ATX power on/off while providing remote management features. The
EIC7700X SoC/SoM communicates with the BMC via UART2, using ESWIN's
protocol. The messages transmitted are fixed sizes (267 bytes), and
depending on the type, can be directional or bi-directional. The
shutdown and cold reboot requests are directional messages from SoC
to BMC (NOTIFY type) with CMD_POWER_OFF or CMD_RESTART. The payload
of shutdown/cold reboot requests should be empty and are ignored by
the BMC at the moment. A HFP (Hifive Premier) specific reset device
is registered in addition to the SoC reset device. For shutdown and
cold reboot, the board-level reset takes precedence.
The definitions of the SoC <-> BMC message protocol is taken from
ESWIN's repo [2]. The only file used from that repo is `hf_common.h`
It's disjunctively dual licensed as (GPL-2.0-only OR BSD-2-Clause),
hence, compatible with the license of OpenSBI. It's heavily modified
and renamed as platform/generic/include/eswin/hfp.h. The author and
copyright in the original file are retained.
Validated shutdown/cold reboot working on Hifive Premier P550.
[1] https://www.sifive.com/boards/hifive-premier-p550#documentation
[2] https://github.com/eswincomputing/hifive-premier-p550-mcu-patches.git
Signed-off-by: Bo Gan <ganboing@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251218104243.562667-8-ganboing@gmail.com
Signed-off-by: Anup Patel <anup@brainfault.org>
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Initial platform support for ESWIN Computing EIC7700 based on public SoC
datasheet[1] and tested on HiFive Premier P550. Vendor U-boot/Linux boots
fine, and I've tested Geekbench 6.5.0 Preview and got scores on par with
the vendor OpenSBI. System shutdown/reboot for HiFive Premier P550 and
other boards will be implemented in subsequent commits. At this point,
only SoC-level warm reset is implemented.
The files and functions are intentionally named as eic770x in many places
for future enhancements to support the 2 die version of the same SoC,
namely EIC7702, seen on DC-ROMA AI PC FML13V03 [2]. This patch set only
deals with the single die version, and the assumption is we can be either
die with id=0 or id=1, but there's only a single die in the system, or we
are only using a single die out of 2. However, the way the SoC handles 2-
die greatly affects how we configure it in a 1-die setup. EIC770X address
map has die 0/1 memory regions interleaved (see comments in eic770x.c).
If only 1 die is connected or active, it creates holes in the address map
for those regions corresponding to the remote die. When speculative-
execution or HW prefetcher touches data-cacheable regions that happen to
fall into those holes, it can trigger bus error. Specifically:
- Remote (non-existent) die L3 zero device
- Remote (non-existent) die cached memory region
- Other holes in Memory Port
To make matters worse, EIC770X doesn't have cache coherent DMA, and due
to the fact that the P550 core lacks Svpbmt, the SoC maps main memory
twice as different regions, so it can bypass cache and fetch the data
directly from memory. In address space, we have two memory regions, one
as cached, the other as uncached. Thus, we also need an extra PMP entry
to protect OpenSBI blob from the uncached window. To do this, platform
code requires single_fw_region, otherwise, we'll run out of PMP entries.
EIC770X also have several feature disable/enable CSRs accessible in M
mode. By default many core features such as speculation and HW prefetch
are disabled, and M mode software is responsible of enabling. Hence,
introduce 4 new build time tunable parameters to Kconfig, which reflects
the values get updated to those CSRs:
- ESWIN_EIC770X_FEAT0_CFG
- ESWIN_EIC770X_FEAT1_CFG
- ESWIN_EIC770X_L1_HWPF_CFG
- ESWIN_EIC770X_L2_HWPF_CFG
The default values are somewhat optimal for generic workloads. They are
dumped when running SiFive's vendor OpenSBI, and in addition, with my
own tuning to address the perf regression reported by drmpeg [3]
To build the firmware+u-boot blob, Use the following, and docs [4] for
testing it with UART boot without flashing:
make FW_TEXT_START=0x80000000 \
FW_PAYLOAD_OFFSET=0x200000 \
FW_PAYLOAD_PATH=u-boot-nodtb.bin \
FW_PAYLOAD_FDT_ADDR=0xf8000000 \
FW_FDT_PATH=u-boot.dtb
[1] https://github.com/eswincomputing/EIC7700X-SoC-Technical-Reference-Manual
[2] https://github.com/geerlingguy/sbc-reviews/issues/82
[3] https://forums.sifive.com/t/low-1-core-stream-bandwidth/7274/15
[4] https://github.com/ganboing/EIC770x-Docs/blob/main/p550/bootchain/UART-Boot.md
Signed-off-by: Bo Gan <ganboing@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251218104243.562667-6-ganboing@gmail.com
Signed-off-by: Anup Patel <anup@brainfault.org>
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