[PATCH 3/5] MIPS: OCTEON: read the L2 crippled fuses from MIO_FUS_DAT3 on OCTEON II

[Orgad Shaneh <orgads@gmail.com>]

prom_init() decides whether to lock lines into the L2 by reading
L2D_FUS3, a CN3XXX/CN5XXX register. On OCTEON II the fuses that cripple
the L2 are MIO_FUS_DAT3[l2c_crip] - which is what cvmx_l2c_get_num_assoc()
already reads for those parts - so the test looks at an address that is
not a register on the chip and gets a meaningless answer: it can skip
L2 locking on a healthy cache, or lock into a reduced one.

Pick the register by family in a small helper.

Assisted-by: Claude:claude-opus-5
Signed-off-by: Orgad Shaneh <orgads@gmail.com>
---
diff --git a/arch/mips/cavium-octeon/setup.c b/arch/mips/cavium-octeon/setup.c
--- a/arch/mips/cavium-octeon/setup.c
+++ b/arch/mips/cavium-octeon/setup.c
@@ -653,6 +653,24 @@ void octeon_user_io_init(void)
 	write_c0_derraddr1(0);
 }
 
+#ifdef CONFIG_CAVIUM_OCTEON_LOCK_L2
+static bool __init octeon_l2_is_crippled(void)
+{
+	/*
+	 * L2D_FUS3 exists on CN3XXX/CN5XXX only. On OCTEON II the
+	 * crippled-L2 fuses live in MIO_FUS_DAT3[l2c_crip].
+	 */
+	if (OCTEON_IS_MODEL(OCTEON_CN6XXX)) {
+		union cvmx_mio_fus_dat3 fus_dat3;
+
+		fus_dat3.u64 = cvmx_read_csr(CVMX_MIO_FUS_DAT3);
+		return fus_dat3.s.l2c_crip != 0;
+	}
+
+	return cvmx_read_csr(CVMX_L2D_FUS3) & (3ull << 34);
+}
+#endif
+
 /**
  * prom_init - Early entry point for arch setup
  */
@@ -801,7 +819,7 @@ void __init prom_init(void)
 	}
 
 #ifdef CONFIG_CAVIUM_OCTEON_LOCK_L2
-	if (cvmx_read_csr(CVMX_L2D_FUS3) & (3ull << 34)) {
+	if (octeon_l2_is_crippled()) {
 		pr_info("Skipping L2 locking due to reduced L2 cache size\n");
 	} else {
 		uint32_t __maybe_unused ebase = read_c0_ebase() & 0x3ffff000;
-- 
2.47.0