On Fri, Jun 14, 2024 at 10:44 AM Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx> wrote: > > > > 在2024年6月14日六月 上午3:32，Huacai Chen写道： > > On Fri, Jun 14, 2024 at 10:25 AM Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx> wrote: > >> > >> > >> > >> 在2024年6月14日六月 上午3:11，Huacai Chen写道： > >> > Hi, Jiaxun, > >> > > >> > On Fri, Jun 14, 2024 at 12:41 AM Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx> wrote: > >> >> > >> >> Most LoongArch 64 machines are using custom "SADR" ACPI extension > >> >> to perform ACPI S3 sleep. However the standard ACPI way to perform > >> >> sleep is to write a value to ACPI PM1/SLEEP_CTL register, and this > >> >> is never supported properly in kernel. > >> > Maybe our hardware is insane so we need "SADR", if so, this patch may > >> > break real hardware. What's your opinion, Jianmin? > >> > >> I understand why your hardware need SADR. Most systems DDR self-refresh > >> mode needs to be setup by firmware. > > _S3 is also a firmware method, why we can't use it to setup self-refresh? > > That's the problem from ACPI spec. As per ACPI spec _S3 method only tells > you what should you write into PM1 or SLEEP_CTL register, it will NOT perform > actual task to enter sleeping. (See 16.1.3.1 [1]) > > On existing LoongArch hardware _S3 method is only used to mark presence of S3 > state. This is violating ACPI spec, but I guess we must live with it. > > Furthermore, on Loongson hardware you have to disable access to DDR memory > to access DDR controller's configuration registers. Which means self-refresh > code must run from BIOS ROM. > > [1]: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/16_Waking_and_Sleeping/sleeping-states.html I think "if (!acpi_gbl_reduced_hardware)" should be before "if (!acpi_sleep_state_supported(ACPI_STATE_S3))", I applied this patch with adjustment. https://github.com/chenhuacai/linux/commit/4bb9e051a4e9430c89ce83ca68a2f5998926e6f6 Huacai > > Thanks > - Jiaxun > > > > > Huacai > > > >> > >> There is no chance that it may break real hardware. When firmware supplied > >> SADR it will always use SADR. The fallback only happens when _S3 method exist > >> but no SADR supplied, which won't happen on real hardware. > >> > >> For QEMU we don't have stub firmware but standard compliant SEEP_CTL is > >> sufficient for entering sleep mode, thus we need this fallback path. > >> > >> Thanks > >> > >> > > >> > Huacai > >> > > >> >> > >> > >> -- > >> - Jiaxun > >> > > -- > - Jiaxun
