Re: [RFC PATCH 2/4] irqchip/riscv-intc: Support large non-standard hwirq number

[Yu-Chien Peter Lin]

On Thu, Sep 07, 2023 at 12:22:55PM +0200, Clément Léger wrote:
> 
> 
> On 07/09/2023 04:16, Yu Chien Peter Lin wrote:
> > Currently, the implementation of the RISC-V INTC driver uses the
> > interrupt cause as hwirq and has a limitation of supporting a
> > maximum of 64 hwirqs. However, according to the privileged spec,
> > interrupt cause >= 16 are defined for platform use.
> > 
> > This limitation prevents us from fully utilizing the available
> > local interrupt sources. Additionally, the hwirqs used on RISC-V
> > are sparse, with only interrupt numbers 1, 5 and 9 (plus Sscofpmf
> > or T-Head's PMU irq) being currently used for supervisor mode.
> > 
> > The patch switches to using irq_domain_create_tree() which
> > creates the radix tree map, allowing us to handle a larger
> > number of hwirqs.
> > 
> > Signed-off-by: Yu Chien Peter Lin <peterlin@xxxxxxxxxxxxx>
> > Reviewed-by: Charles Ci-Jyun Wu <dminus@xxxxxxxxxxxxx>
> > Reviewed-by: Leo Yu-Chi Liang <ycliang@xxxxxxxxxxxxx>
> > 
> > ---
> > There are 3 hwirqs of local interrupt source exceed 64 defined in
> > AX45MP datasheet [1] Table 56: AX45MP-1C scause Value After Trap:
> > - 256+16 Slave port ECC error interrupt (S-mode)
> > - 256+17 Bus write transaction error interrupt (S-mode)
> > - 256+18 Performance monitor overflow interrupt(S-mode)
> > 
> > [1] http://www.andestech.com/wp-content/uploads/AX45MP-1C-Rev.-5.0.0-Datasheet.pdf
> > ---
> >  drivers/irqchip/irq-riscv-intc.c | 10 ++++------
> >  1 file changed, 4 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
> > index 4adeee1bc391..76e1229c45de 100644
> > --- a/drivers/irqchip/irq-riscv-intc.c
> > +++ b/drivers/irqchip/irq-riscv-intc.c
> > @@ -24,8 +24,8 @@ static asmlinkage void riscv_intc_irq(struct pt_regs *regs)
> >  {
> >  	unsigned long cause = regs->cause & ~CAUSE_IRQ_FLAG;
> >  
> > -	if (unlikely(cause >= BITS_PER_LONG))
> > -		panic("unexpected interrupt cause");
> > +	if (!irq_find_mapping(intc_domain, cause))
> > +		panic("unexpected interrupt cause: %ld", cause);
> 
> Hi Yu,
> 
> It seems like generic_handle_domain_irq() returns -EINVAL if provided
> with NULL (which will happen if the interrupt does not have a mapping
> due to __irq_resolve_mapping returning NULL) so maybe it is possible to
> remove this check (since __irq_resolve_mapping() is also called by
> generic_handle_domain_irq()) and panic if generic_handle_domain_irq()
> returns -EINVAL ? That would avoid calling __irq_resolve_mapping() twice
> for really rare cases.
> 
> Clément

Hi Clément,

Thanks for catching this, will fix it in the patch v2.

Best regards,
Peter Lin