> Date: Mon, 27 Jan 2025 14:48:55 +0000 > From: Sam Day <[email protected]>
Hi Sam, > Most MSM8916 devices shipped without PSCI support. The history is quite > nuanced (a good overview can be found in [1]), but the end result is > that the upstream DTs for this SoC pretend that PSCI exists, and it's > expected that the bootloader handles the case where it doesn't. This is > codified by the de-facto bootloader for MSM8916 devices, lk2nd [2]. > > So we handle it here by deleting the /psci node if we detect the absence > of PSCI. We need to do this early to ensure sysreset works correctly, > since the PSCI firmware driver is PRE_RELOC and binds the PSCI sysreset > driver. But deleting the /psci node isn't enough is it? At least on systems with more than a single core the OS will need a way to spin up the additonal cores. So you'll need to modify the CPU nodes as well and change the "enable-method" property to "spin-table" and add the necessary infrastructure for that. > Additionally, show_psci_version is updated to check that PSCI exists. > Currently this banner outputs "PSCI: 65535.65535" on devices without > PSCI support, which isn't very useful :) > > [1]: https://github.com/msm8916-mainline/linux/issues/388 > [2]: > https://github.com/msm8916-mainline/lk2nd/blob/8183ea2/lk2nd/smp/spin-table/spin-table.c#L237 > > Signed-off-by: Sam Day <[email protected]> > --- > arch/arm/mach-snapdragon/board.c | 43 > ++++++++++++++++++++++++++++++++++++---- > 1 file changed, 39 insertions(+), 4 deletions(-) > > diff --git a/arch/arm/mach-snapdragon/board.c > b/arch/arm/mach-snapdragon/board.c > index > e87551784b8d7afb4186533d43b8bddacba9faec..75b9cf1a8a1b3383665eb2d4e6725efe59718de0 > 100644 > --- a/arch/arm/mach-snapdragon/board.c > +++ b/arch/arm/mach-snapdragon/board.c > @@ -162,11 +162,42 @@ static void show_psci_version(void) > > arm_smccc_smc(ARM_PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0, 0, 0, 0, 0, &res); > > + /* Some older SoCs like MSM8916 don't always support PSCI */ > + if ((int)res.a0 == PSCI_RET_NOT_SUPPORTED) > + return; > + > debug("PSCI: v%ld.%ld\n", > PSCI_VERSION_MAJOR(res.a0), > PSCI_VERSION_MINOR(res.a0)); > } > > +/** > + * Most MSM8916 devices in the wild shipped without PSCI support, but the > + * upstream DTs pretend that PSCI exists. If that situation is detected here, > + * the /psci node is deleted. This is done very early to ensure the PSCI > + * firmware driver doesn't bind (which then binds a sysreset driver that > won't > + * work). > + */ > +static void qcom_psci_fixup(void *fdt) > +{ > + int offset, ret; > + struct arm_smccc_res res; > + > + arm_smccc_smc(ARM_PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0, 0, 0, 0, 0, &res); > + > + if ((int)res.a0 != PSCI_RET_NOT_SUPPORTED) > + return; > + > + offset = fdt_path_offset(fdt, "/psci"); > + if (offset < 0) > + return; > + > + debug("Found /psci DT node on device with no PSCI. Deleting.\n"); > + ret = fdt_del_node(fdt, offset); > + if (ret) > + log_err("Failed to delete /psci node: %d\n", ret); > +} > + > /* We support booting U-Boot with an internal DT when running as a > first-stage bootloader > * or for supporting quirky devices where it's easier to leave the > downstream DT in place > * to improve ABL compatibility. Otherwise, we use the DT provided by ABL. > @@ -212,12 +243,16 @@ int board_fdt_blob_setup(void **fdtp) > > if (internal_valid) { > debug("Using built in FDT\n"); > - return -EEXIST; > + ret = -EEXIST; > + } else { > + debug("Using external FDT\n"); > + *fdtp = external_fdt; > + ret = 0; > } > > - debug("Using external FDT\n"); > - *fdtp = external_fdt; > - return 0; > + qcom_psci_fixup(*fdtp); > + > + return ret; > } > > void reset_cpu(void) > > --- > base-commit: 2eed5a1ff36217372e19f7513bd07077fc76718a > change-id: 20250127-qcom-handle-absent-psci-6e8e8af7bcd7 > prerequisite-change-id: 20250120-qcom-parse-memory-updates-96ffe248cdf1:v3 > prerequisite-patch-id: 65448b5a93120d2117c1361035afc9bd911d005f > > Best regards, > -- > Sam Day <[email protected]> > > >
