[RFC PATCH v2 3/7] platform: generic: introduce fw_platform_get_reserved_pmp_count()

[Yu-Chien Peter Lin]

Introduce fw_platform_get_reserved_pmp_count() to parse the
`reserved-pmp-count` property from the opensbi-config node.

Since mseccfg.{RLB,MMWP,MML} are sticky bits, we can't poll them
to detect the presence of Smempp. Therefore, the only way is to
parse it from FDT `riscv,isa-extensions` or `riscv,isa`.

Signed-off-by: Yu-Chien Peter Lin <peter.lin at sifive.com>
---
 platform/generic/platform.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/platform/generic/platform.c b/platform/generic/platform.c
index 91140958..936e5356 100644
--- a/platform/generic/platform.c
+++ b/platform/generic/platform.c
@@ -66,6 +66,35 @@ default_config:
 	return fw_platform_calculate_heap_size(hart_count);
 }
 
+static u32 fw_platform_get_reserved_pmp_count(const void *fdt)
+{
+	int chosen_offset, config_offset, len;
+	u32 reserved_pmp_count = 0;
+	const fdt32_t *val;
+
+	/*
+	 * If smepmp is enabled, minimal 1 entry is required
+	 * by sbi_hart_map_saddr().
+	 */
+	if (fdt_has_isa_extension(fdt, "smepmp"))
+		reserved_pmp_count = 1;
+
+	chosen_offset = fdt_path_offset(fdt, "/chosen");
+	if (chosen_offset < 0)
+		goto out;
+
+	config_offset = fdt_node_offset_by_compatible(fdt, chosen_offset, "opensbi,config");
+	if (config_offset < 0)
+		goto out;
+
+	val = (fdt32_t *)fdt_getprop(fdt, config_offset, "reserved-pmp-count", &len);
+	if (len > 0 && val)
+		return fdt32_to_cpu(*val) + reserved_pmp_count;
+
+out:
+	return reserved_pmp_count;
+}
+
 extern struct sbi_platform platform;
 static bool platform_has_mlevel_imsic = false;
 static u32 generic_hart_index2id[SBI_HARTMASK_MAX_BITS] = { 0 };
@@ -184,6 +213,8 @@ unsigned long fw_platform_init(unsigned long arg0, unsigned long arg1,
 
 	platform.hart_count = hart_count;
 	platform.heap_size = fw_platform_get_heap_size(fdt, hart_count);
+	platform.reserved_pmp_count = fw_platform_get_reserved_pmp_count(fdt);
+
 	platform_has_mlevel_imsic = fdt_check_imsic_mlevel(fdt);
 	platform.cbom_block_size = cbom_block_size;
 
-- 
2.39.3