On 25/07/18 10:36, Christoph Hellwig wrote:
> From: Palmer Dabbelt <palmer@xxxxxxxxxxx>
>
> This patch adds a driver that manages the local interrupts on each
> RISC-V hart, as specifiec by the RISC-V supervisor level ISA manual.
> The local interrupt controller manages software interrupts, timer
> interrupts, and hardware interrupts (which are routed via the
> platform level interrupt controller). Per-hart local interrupt
> controllers are found on all RISC-V systems.
>
> Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxx>
> [hch: Kconfig simplifications, various cleanups]
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> drivers/irqchip/Kconfig | 4 +
> drivers/irqchip/Makefile | 1 +
> drivers/irqchip/irq-riscv-intc.c | 197 +++++++++++++++++++++++++++++++
> 3 files changed, 202 insertions(+)
> create mode 100644 drivers/irqchip/irq-riscv-intc.c
>
[...]
> +/*
> + * On RISC-V systems local interrupts are masked or unmasked by writing the SIE
> + * (Supervisor Interrupt Enable) CSR. As CSRs can only be written on the local
> + * hart, these functions can only be called on the hart that corresponds to the
> + * IRQ chip. They are only called internally to this module, so they BUG_ON if
> + * this condition is violated rather than attempting to handle the error by
> + * forwarding to the target hart, as that's already expected to have been done.
> + */
> +static void riscv_irq_mask(struct irq_data *d)
> +{
> + struct riscv_irq_data *data = irq_data_get_irq_chip_data(d);
> +
> + BUG_ON(smp_processor_id() != data->hart);
> + csr_clear(sie, 1 << d->hwirq);
> +}
> +
> +static void riscv_irq_unmask(struct irq_data *d)
> +{
> + struct riscv_irq_data *data = irq_data_get_irq_chip_data(d);
> +
> + BUG_ON(smp_processor_id() != data->hart);
> + csr_set(sie, 1 << d->hwirq);
> +}
> +
> +/* Callbacks for twiddling SIE on another hart. */
> +static void riscv_irq_enable_helper(void *d)
> +{
> + riscv_irq_unmask(d);
> +}
> +
> +static void riscv_irq_disable_helper(void *d)
> +{
> + riscv_irq_mask(d);
> +}
> +
> +static void riscv_remote_ctrl(unsigned int cpu, void (*fn)(void *d),
> + struct irq_data *data)
> +{
> + smp_call_function_single(cpu, fn, data, true);
> +}
> +
> +static void riscv_irq_enable(struct irq_data *d)
> +{
> + struct riscv_irq_data *data = irq_data_get_irq_chip_data(d);
> +
> + /*
> + * It's only possible to write SIE on the current hart. This jumps
> + * over to the target hart if it's not the current one. It's invalid
> + * to write SIE on a hart that's not currently running.
> + */
> + if (data->hart == smp_processor_id())
> + riscv_irq_unmask(d);
> + else if (cpu_online(data->hart))
> + riscv_remote_ctrl(data->hart, riscv_irq_enable_helper, d);
This feels odd. It means that you cannot have the following sequence:
local_irq_disable();
enable_irq(x); // where x is owned by a remote hart
as smp_call_function_single() requires interrupts to be enabled.
More fundamentally, why are you trying to make these interrupts look
global while they aren't? arm/arm64 have similar restrictions with GICv2
and earlier, and treats these interrupts as per-cpu.
Given that the drivers that deal with drivers connected to the per-hart
irqchip are themselves likely to be aware of the per-cpu aspect, it
would make sense to align things (we've been through that same
discussion about the clocksource driver a few weeks back).
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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