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lib: utils/irqchip: Match against more specific compatible strings first

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The T-HEAD C90x PLIC has some special quirks, such as the S-mode
delegation bit. OpenSBI currently handles this by checking the compatible
string in the device tree.

However, this matching is done in the order of the fdt_match array. So if
a device tree contains both strings, for example:

	compatible = "thead,c900-plic", "riscv,plic0";

Then OpenSBI will match against the generic "riscv,plic0" string, since
that appears first in the fdt_match array. This means it will fail to set
the S-mode delegation bit, and Linux will fail to boot. In some cases, it
is not possible to change the compatible string to just the T-HEAD PLIC,
as older versions of Linux only recognize the RISC-V compatible string.

This patch fixes that by moving the RISC-V string to the end, ensuring
that the more specific options get matched first.

Signed-off-by: Alex Studer <alex@studer.dev>
Reviewed-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Alex Studer
2025-02-14 01:27:38 -05:00
committed by Anup Patel
parent a2c172f526
commit 6019259dfb
1 changed files with 7 additions and 1 deletions
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8
lib/utils/irqchip/fdt_irqchip_plic.c
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@@ -98,10 +98,16 @@ fail_free_data:
static const struct fdt_match irqchip_plic_match[] = {
{ .compatible = "andestech,nceplic100" },
{ .compatible = "riscv,plic0" },
{ .compatible = "sifive,plic-1.0.0" },
{ .compatible = "thead,c900-plic",
.data = (void *)(PLIC_FLAG_THEAD_DELEGATION | PLIC_FLAG_ENABLE_PM) },
/*
* We keep the generic RISC-V PLIC at the end.
* This ensures we match against more specific options first.
* (This is important if the PLIC has quirks, like the T-HEAD PLIC.)
*/
{ .compatible = "riscv,plic0" },
{ /* sentinel */ }
};