On Sat, Aug 31, 2024, at 07:48, Nick Chan wrote:
> From: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxx>
>
> Starting from the A11 (T8015) SoC, Apple introuced system registers for
> fast IPI and UNCORE PMC control. These sysregs do not exist on earlier
> A7-A10 SoCs and trying to access them results in an instant crash.
>
> Restrict sysreg access within the AIC driver to configurations where
> use_fast_ipi is true to allow AIC to function properly on A7-A10 SoCs.
> As part of the restriction, the IPI-always-ack path in aic_handle_fiq()
> has been removed. If the code path were to be reached, the system is
> fast IPI capable and one of the fast IPI compatibles should be used
> instead.
The last part is a bit weird. This is really just a bug in the driver.
We either have a system with fastipi and then we can handle it.
Or we have a system without fastipi and we shouldn't even try to read
SYS_IMP_APL_IPI_SR_EL1.
Your first sentence "Restrict sysreg access within the AIC driver to
configurations where use_fast_ipi is true to allow AIC to function properly
on A7-A10 SoCs." already explains what's going on here. You're fixing
a bug where we tried to access SYS_IMP_APL_IPI_SR_EL1 unconditionally.
It just didn't matter so far because there's only upstream support
for M1+ where SYS_IMP_APL_IPI_SR_EL1 always exist.
With a fixed commit message:
Reviewed-by: Sven Peter <sven@xxxxxxxxxxxxx>
>
> Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxxxxxx>
> Co-developed-by: Nick Chan <towinchenmi@xxxxxxxxx>
> Signed-off-by: Nick Chan <towinchenmi@xxxxxxxxx>
> ---
> drivers/irqchip/irq-apple-aic.c | 25 ++++++++++++-------------
> 1 file changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c
> index 01a3c79054f5..a6d812afb10d 100644
> --- a/drivers/irqchip/irq-apple-aic.c
> +++ b/drivers/irqchip/irq-apple-aic.c
> @@ -234,6 +234,7 @@ enum fiq_hwirq {
> AIC_NR_FIQ
> };
>
> +/* True if UNCORE/UNCORE2 and Sn_... IPI registers are present and
> used (A11+) */
> static DEFINE_STATIC_KEY_TRUE(use_fast_ipi);
> /* True if SYS_IMP_APL_IPI_RR_LOCAL_EL1 exists for local fast IPIs
> (M1+) */
> static DEFINE_STATIC_KEY_TRUE(use_local_fast_ipi);
> @@ -550,14 +551,9 @@ static void __exception_irq_entry
> aic_handle_fiq(struct pt_regs *regs)
> * we check for everything here, even things we don't support yet.
> */
>
> - if (read_sysreg_s(SYS_IMP_APL_IPI_SR_EL1) & IPI_SR_PENDING) {
> - if (static_branch_likely(&use_fast_ipi)) {
> - aic_handle_ipi(regs);
> - } else {
> - pr_err_ratelimited("Fast IPI fired. Acking.\n");
> - write_sysreg_s(IPI_SR_PENDING, SYS_IMP_APL_IPI_SR_EL1);
> - }
> - }
> + if (static_branch_likely(&use_fast_ipi) &&
> + (read_sysreg_s(SYS_IMP_APL_IPI_SR_EL1) & IPI_SR_PENDING))
> + aic_handle_ipi(regs);
>
> if (TIMER_FIRING(read_sysreg(cntp_ctl_el0)))
> generic_handle_domain_irq(aic_irqc->hw_domain,
> @@ -592,8 +588,9 @@ static void __exception_irq_entry
> aic_handle_fiq(struct pt_regs *regs)
> AIC_FIQ_HWIRQ(irq));
> }
>
> - if (FIELD_GET(UPMCR0_IMODE, read_sysreg_s(SYS_IMP_APL_UPMCR0_EL1)) ==
> UPMCR0_IMODE_FIQ &&
> - (read_sysreg_s(SYS_IMP_APL_UPMSR_EL1) & UPMSR_IACT)) {
> + if (static_branch_likely(&use_fast_ipi) &&
> + (FIELD_GET(UPMCR0_IMODE, read_sysreg_s(SYS_IMP_APL_UPMCR0_EL1))
> == UPMCR0_IMODE_FIQ) &&
> + (read_sysreg_s(SYS_IMP_APL_UPMSR_EL1) & UPMSR_IACT)) {
> /* Same story with uncore PMCs */
> pr_err_ratelimited("Uncore PMC FIQ fired. Masking.\n");
> sysreg_clear_set_s(SYS_IMP_APL_UPMCR0_EL1, UPMCR0_IMODE,
> @@ -830,7 +827,8 @@ static int aic_init_cpu(unsigned int cpu)
> /* Mask all hard-wired per-CPU IRQ/FIQ sources */
>
> /* Pending Fast IPI FIQs */
> - write_sysreg_s(IPI_SR_PENDING, SYS_IMP_APL_IPI_SR_EL1);
> + if (static_branch_likely(&use_fast_ipi))
> + write_sysreg_s(IPI_SR_PENDING, SYS_IMP_APL_IPI_SR_EL1);
>
> /* Timer FIQs */
> sysreg_clear_set(cntp_ctl_el0, 0, ARCH_TIMER_CTRL_IT_MASK);
> @@ -851,8 +849,9 @@ static int aic_init_cpu(unsigned int cpu)
> FIELD_PREP(PMCR0_IMODE, PMCR0_IMODE_OFF));
>
> /* Uncore PMC FIQ */
> - sysreg_clear_set_s(SYS_IMP_APL_UPMCR0_EL1, UPMCR0_IMODE,
> - FIELD_PREP(UPMCR0_IMODE, UPMCR0_IMODE_OFF));
> + if (static_branch_likely(&use_fast_ipi))
> + sysreg_clear_set_s(SYS_IMP_APL_UPMCR0_EL1, UPMCR0_IMODE,
> + FIELD_PREP(UPMCR0_IMODE, UPMCR0_IMODE_OFF));
>
> /* Commit all of the above */
> isb();
> --
> 2.46.0
