[PATCH] lib: sbi: Fix hw a/d updating defaults

[Andrew Jones]

The Svade dt-binding description states that Svadu should only
be enabled at boot time when only Svadu is present in the DT.
Ensure that's the case. Also, when only Svadu is supported,
disable FWFT.PTE_AD_HW_UPDATING, as we need both to support
toggling.

Signed-off-by: Andrew Jones <andrew.jones at oss.qualcomm.com>
---
 lib/sbi/sbi_fwft.c | 10 +++++++++-
 lib/sbi/sbi_hart.c | 18 ++++++++++--------
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/lib/sbi/sbi_fwft.c b/lib/sbi/sbi_fwft.c
index 373140b746bd..574b875e408d 100644
--- a/lib/sbi/sbi_fwft.c
+++ b/lib/sbi/sbi_fwft.c
@@ -160,8 +160,16 @@ static int fwft_get_double_trap(struct fwft_config *conf, unsigned long *value)
 
 static int fwft_adue_supported(struct fwft_config *conf)
 {
+	/*
+	 * FWFT.PTE_AD_HW_UPDATING is only supported when both Svade and Svadu
+	 * are supported. We need both in order to support toggling and to
+	 * ensure the reset value of zero is valid (it wouldn't be when only
+	 * Svadu is supported).
+	 */
 	if (!sbi_hart_has_extension(sbi_scratch_thishart_ptr(),
-				    SBI_HART_EXT_SVADU))
+				    SBI_HART_EXT_SVADU) ||
+	    !sbi_hart_has_extension(sbi_scratch_thishart_ptr(),
+				    SBI_HART_EXT_SVADE))
 		return SBI_ENOTSUPP;
 
 	return SBI_OK;
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 99e13990aa60..0df11d0d1029 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -137,6 +137,9 @@ static void mstatus_init(struct sbi_scratch *scratch)
 	if (sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_12) {
 		menvcfg_val = csr_read64(CSR_MENVCFG);
 
+		/* Disable HW A/D updating by default */
+		menvcfg_val &= ~ENVCFG_ADUE;
+
 		/* Disable double trap by default */
 		menvcfg_val &= ~ENVCFG_DTE;
 
@@ -158,18 +161,17 @@ static void mstatus_init(struct sbi_scratch *scratch)
 #endif
 		__set_menvcfg_ext(SBI_HART_EXT_SSTC, ENVCFG_STCE)
 		__set_menvcfg_ext(SBI_HART_EXT_SMCDELEG, ENVCFG_CDE);
-		__set_menvcfg_ext(SBI_HART_EXT_SVADU, ENVCFG_ADUE);
-
-#undef __set_menvcfg_ext
 
 		/*
-		 * When both Svade and Svadu are present in DT, the default scheme for managing
-		 * the PTE A/D bits should use Svade. Check Svadu before Svade extension to ensure
-		 * that the ADUE bit is cleared when the Svade support are specified.
+		 * Assume only Svadu is supported when it is the only extension
+		 * present in the ISA string. Svade is assumed when neither are
+		 * present. When both are present we must default to Svade (see
+		 * the zero reset value of FWFT.PTE_AD_HW_UPDATING).
 		 */
+		if (!sbi_hart_has_extension(scratch, SBI_HART_EXT_SVADE))
+			__set_menvcfg_ext(SBI_HART_EXT_SVADU, ENVCFG_ADUE);
 
-		if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SVADE))
-			menvcfg_val &= ~ENVCFG_ADUE;
+#undef __set_menvcfg_ext
 
 		csr_write64(CSR_MENVCFG, menvcfg_val);
 
-- 
2.43.0