rust: pl011: extend registers to 32 bits

The PL011 Technical Reference Manual lists the "real" size of the
registers in table 3-1, and only rounds up to the next byte when
describing the registers; for example, UARTDR is listed as having
width 12/8 (12 bits read, 8 written) and only bits 15:0 are listed
in "Table 3-2 UARTDR Register".

However, in practice these are 32-bit registers, accessible only
through 32-bit MMIO accesses; preserving the fiction that they're
smaller introduces multiple casts (to go from the bilge bitfield
type to e.g u16 to u64) and more importantly it breaks the
migration stream because the Rust vmstate macros are not yet
type safe.

So, just make everything 32-bits wide.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 10 insertions, 13 deletions

diff --git a/rust/hw/char/pl011/src/lib.rs b/rust/hw/char/pl011/src/lib.rs
index 463ae60543..0747e130ca 100644
--- a/rust/hw/char/pl011/src/lib.rs
+++ b/rust/hw/char/pl011/src/lib.rs
@@ -131,12 +131,6 @@ impl core::convert::TryFrom<u64> for RegisterOffset {
 pub mod registers {
     //! Device registers exposed as typed structs which are backed by arbitrary
     //! integer bitmaps. [`Data`], [`Control`], [`LineControl`], etc.
-    //!
-    //! All PL011 registers are essentially 32-bit wide, but are typed here as
-    //! bitmaps with only the necessary width. That is, if a struct bitmap
-    //! in this module is for example 16 bits long, it should be conceived
-    //! as a 32-bit register where the unmentioned higher bits are always
-    //! unused thus treated as zero when read or written.
     use bilge::prelude::*;
 
     /// Receive Status Register / Data Register common error bits
@@ -234,10 +228,11 @@ pub mod registers {
     /// # Source
     /// ARM DDI 0183G 3.3.2 Receive Status Register/Error Clear Register,
     /// UARTRSR/UARTECR
-    #[bitsize(8)]
+    #[bitsize(32)]
     #[derive(Clone, Copy, DebugBits, FromBits)]
     pub struct ReceiveStatusErrorClear {
         pub errors: Errors,
+        _reserved_unpredictable: u24,
     }
 
     impl ReceiveStatusErrorClear {
@@ -257,7 +252,7 @@ pub mod registers {
         }
     }
 
-    #[bitsize(16)]
+    #[bitsize(32)]
     #[derive(Clone, Copy, DebugBits, FromBits)]
     /// Flag Register, `UARTFR`
     #[doc(alias = "UARTFR")]
@@ -309,7 +304,7 @@ pub mod registers {
         pub transmit_fifo_empty: bool,
         /// `RI`, is `true` when `nUARTRI` is `LOW`.
         pub ring_indicator: bool,
-        _reserved_zero_no_modify: u7,
+        _reserved_zero_no_modify: u23,
     }
 
     impl Flags {
@@ -328,7 +323,7 @@ pub mod registers {
         }
     }
 
-    #[bitsize(16)]
+    #[bitsize(32)]
     #[derive(Clone, Copy, DebugBits, FromBits)]
     /// Line Control Register, `UARTLCR_H`
     #[doc(alias = "UARTLCR_H")]
@@ -382,8 +377,8 @@ pub mod registers {
         /// the PEN bit disables parity checking and generation. See Table 3-11
         /// on page 3-14 for the parity truth table.
         pub sticky_parity: bool,
-        /// 15:8 - Reserved, do not modify, read as zero.
-        _reserved_zero_no_modify: u8,
+        /// 31:8 - Reserved, do not modify, read as zero.
+        _reserved_zero_no_modify: u24,
     }
 
     impl LineControl {
@@ -454,7 +449,7 @@ pub mod registers {
     ///
     /// # Source
     /// ARM DDI 0183G, 3.3.8 Control Register, `UARTCR`, Table 3-12
-    #[bitsize(16)]
+    #[bitsize(32)]
     #[doc(alias = "UARTCR")]
     #[derive(Clone, Copy, DebugBits, FromBits)]
     pub struct Control {
@@ -532,6 +527,8 @@ pub mod registers {
         /// CTS hardware flow control is enabled. Data is only transmitted when
         /// the `nUARTCTS` signal is asserted.
         pub cts_hardware_flow_control_enable: bool,
+        /// 31:16 - Reserved, do not modify, read as zero.
+        _reserved_zero_no_modify2: u16,
     }
 
     impl Control {