[PATCH 15/17] lib: utils/irqchip: Use scratch space to save per-HART PLIC pointer

[Anup Patel]

On Mon, Jun 5, 2023 at 12:27 PM Jessica Clarke <jrtc27 at jrtc27.com> wrote:
>
> On 5 Jun 2023, at 07:51, Anup Patel <anup at brainfault.org> wrote:
> >
> > On Mon, Jun 5, 2023 at 11:13 AM Jessica Clarke <jrtc27 at jrtc27.com> wrote:
> >>
> >> On 25 Apr 2023, at 13:32, Anup Patel <apatel at ventanamicro.com> wrote:
> >>>
> >>> Instead of using a global array indexed by hartid, we should use
> >>> scratch space to save per-HART PLIC pointer and PLIC context numbers.
> >>>
> >>> Signed-off-by: Anup Patel <apatel at ventanamicro.com>
> >>> ---
> >>> lib/utils/irqchip/fdt_irqchip_plic.c | 108 +++++++++++++++++++++------
> >>> 1 file changed, 86 insertions(+), 22 deletions(-)
> >>>
> >>> diff --git a/lib/utils/irqchip/fdt_irqchip_plic.c b/lib/utils/irqchip/fdt_irqchip_plic.c
> >>> index 605f44a..eb1e412 100644
> >>> --- a/lib/utils/irqchip/fdt_irqchip_plic.c
> >>> +++ b/lib/utils/irqchip/fdt_irqchip_plic.c
> >>> @@ -12,54 +12,97 @@
> >>> #include <sbi/riscv_io.h>
> >>> #include <sbi/sbi_error.h>
> >>> #include <sbi/sbi_heap.h>
> >>> -#include <sbi/sbi_hartmask.h>
> >>> +#include <sbi/sbi_scratch.h>
> >>> #include <sbi_utils/fdt/fdt_helper.h>
> >>> #include <sbi_utils/irqchip/fdt_irqchip.h>
> >>> #include <sbi_utils/irqchip/plic.h>
> >>>
> >>> -static struct plic_data *plic_hartid2data[SBI_HARTMASK_MAX_BITS];
> >>> -static int plic_hartid2context[SBI_HARTMASK_MAX_BITS][2] = { { -1 } };
> >>> +static unsigned long plic_ptr_offset;
> >>> +
> >>> +#define plic_get_hart_data_ptr(__scratch) \
> >>> +({ \
> >>> + (void *)(*((ulong *)sbi_scratch_offset_ptr((__scratch), \
> >>> +   plic_ptr_offset))); \
> >>
> >> Why all the casting rather than just storing the pointer?
> >
> > We are storing pointer value in scratch space as ulong but
> > sbi_scratch_offset_ptr() returns a void pointer to a location in
> > scratch space so we have to do the above casting for getting
> > the pointer stored in scratch space.
> >
> > Thinking about this more, it is better to have generic helper
> > macros in sbi_scartch.h so that we don't have to define it
> > everywhere.
>
> Pointers are not longs. This isn’t the Linux kernel, you don’t
> need to be allergic to using the correct types for things.
>

Okay, I will improve this in v2.

Regards,
Anup