Re: [PATCH] of: property: Fix fw_devlink handling of interrupt-map

[Anup Patel <apatel@xxxxxxxxxxxxxxxx>]

On Tue, May 28, 2024 at 10:11 PM Marc Zyngier <maz@xxxxxxxxxx> wrote:
>
> Commit d976c6f4b32c ("of: property: Add fw_devlink support for
> interrupt-map property") tried to do what it says on the tin,
> but failed on a couple of points:
>
> - it confuses bytes and cells. Not a huge deal, except when it
>   comes to pointer arithmetic
>
> - it doesn't really handle anything but interrupt-maps that have
>   their parent #address-cells set to 0
>
> The combinations of the two leads to some serious fun on my M1
> box, with plenty of WARN-ON() firing all over the shop, and
> amusing values being generated for interrupt specifiers.
>
> Address both issues so that I can boot my machines again.
>
> Fixes: d976c6f4b32c ("of: property: Add fw_devlink support for interrupt-map property")
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> Cc: Saravana Kannan <saravanak@xxxxxxxxxx>
> Cc: Rob Herring (Arm) <robh@xxxxxxxxxx>

Thanks for the fix patch but unfortunately it breaks for RISC-V.

> ---
>  drivers/of/property.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 1c83e68f805b..9adebc63bea9 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -1322,7 +1322,13 @@ static struct device_node *parse_interrupt_map(struct device_node *np,
>         addrcells = of_bus_n_addr_cells(np);
>
>         imap = of_get_property(np, "interrupt-map", &imaplen);
> -       if (!imap || imaplen <= (addrcells + intcells))
> +       imaplen /= sizeof(*imap);
> +
> +       /*
> +        * Check that we have enough runway for the child unit interrupt
> +        * specifier and a phandle. That's the bare minimum we can expect.
> +        */
> +       if (!imap || imaplen <= (addrcells + intcells + 1))
>                 return NULL;
>         imap_end = imap + imaplen;
>
> @@ -1346,8 +1352,14 @@ static struct device_node *parse_interrupt_map(struct device_node *np,
>                 if (!index)
>                         return sup_args.np;
>
> -               of_node_put(sup_args.np);
> +               /*
> +                * Account for the full parent unit interrupt specifier
> +                * (address cells, interrupt cells, and phandle).
> +                */
> +               imap += of_bus_n_addr_cells(sup_args.np);

This breaks for RISC-V because we don't have "#address-cells"
property in interrupt controller DT node and of_bus_n_addr_cells()
retrieves "#address-cells" from the parent of interrupt controller.

The of_irq_parse_raw() looks for "#address-cells" property
in the interrupt controller DT node only so we should do a
similar thing here as well.

The below change on top of this patch worked for me.

diff --git a/drivers/of/property.c b/drivers/of/property.c
index 9adebc63bea9..f54da2989ea9 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -1308,7 +1308,7 @@ static struct device_node
*parse_interrupt_map(struct device_node *np,
 {
     const __be32 *imap, *imap_end, *addr;
     struct of_phandle_args sup_args;
-    u32 addrcells, intcells;
+    u32 addrcells, intcells, paddrcells;
     int i, imaplen;

     if (!IS_ENABLED(CONFIG_OF_IRQ))
@@ -1356,7 +1356,8 @@ static struct device_node
*parse_interrupt_map(struct device_node *np,
          * Account for the full parent unit interrupt specifier
          * (address cells, interrupt cells, and phandle).
          */
-        imap += of_bus_n_addr_cells(sup_args.np);
+        if (!of_property_read_u32(sup_args.np, "#address-cells", &paddrcells))
+            imap += paddrcells;
         imap += sup_args.args_count + 1;

         of_node_put(sup_args.np);

<snip>

Regards,
Anup