[PATCH 08/26] hw/sd: sdhci: Accept version 4 enable without UHS-I

[Bin Meng <bin.meng@processmission.com>]

Host Control 2 writes have been conditional on modeled UHS-I support
since commit 0034ebe6ee31. Host Version 4 Enable does not control UHS
signaling, so controllers without modeled UHS-I cannot enter version
4 mode.

Retain Host Version 4 Enable independently of UHS-I while continuing
to reject UHS-specific fields and keeping voltage changes UHS-gated.

Fixes: 0034ebe6ee31 ("sdhci: implement UHS-I voltage switch")
Cc: qemu-stable@nongnu.org
Signed-off-by: Bin Meng <bin.meng@processmission.com>
---

 hw/sd/sdhci.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
index 749de85476..71af1f8c57 100644
--- a/hw/sd/sdhci.c
+++ b/hw/sd/sdhci.c
@@ -1358,11 +1358,24 @@ sdhci_write(void *opaque, hwaddr offset, uint64_t val, unsigned size)
         }
         sdhci_update_irq(s);
         break;
-    case SDHC_ACMD12ERRSTS:
+    case SDHC_ACMD12ERRSTS: {
+        uint16_t hostctl2_mask = mask >> 16;
+        uint16_t hostctl2_value = value >> 16;
+
         MASKED_WRITE(s->acmd12errsts, mask, value & UINT16_MAX);
-        if (s->uhs_mode >= UHS_I) {
-            MASKED_WRITE(s->hostctl2, mask >> 16, value >> 16);
+        if (s->uhs_mode < UHS_I) {
+            /*
+             * VERSION4 is writable even without UHS-I. Preserve all other
+             * Host Control 2 bits when UHS-I is not supported.
+             */
+            uint16_t independent = R_SDHC_HOSTCTL2_VERSION4_MASK;
 
+            hostctl2_mask |= ~independent;
+            hostctl2_value &= independent;
+        }
+        MASKED_WRITE(s->hostctl2, hostctl2_mask, hostctl2_value);
+
+        if (s->uhs_mode >= UHS_I) {
             if (FIELD_EX32(s->hostctl2, SDHC_HOSTCTL2, V18_ENA)) {
                 sdbus_set_voltage(&s->sdbus, SD_VOLTAGE_1_8V);
             } else {
@@ -1370,6 +1383,7 @@ sdhci_write(void *opaque, hwaddr offset, uint64_t val, unsigned size)
             }
         }
         break;
+    }
 
     case SDHC_CAPAB:
     case SDHC_CAPAB + 4:
-- 
2.34.1