There are implementations of the PL011 that can only handle 32-bit
accesses (i.e. no 16-bit or 8-bit), usually advertised by 'reg-io-width'
dt property set to 4. On such UARTs, the current early printk code for
arm64 does not work. To fix this issue, make all the accesses to be 32-bit
by using ldr, str without a size field. This makes it possible to use
early printk on such platforms, while all the other implementations should
generally cope with 32-bit accesses. In case they do not, they would
already fail as we explicitly use writel/readl in the runtime driver to
maintain broader compatibility and to be SBSAv2 compliant. Therefore, this
change makes the runtime/early handling consistent (also it matches the
arm32 debug-pl011 code).
Signed-off-by: Michal Orzel <michal.or...@amd.com>
---
xen/arch/arm/arm64/debug-pl011.inc | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/xen/arch/arm/arm64/debug-pl011.inc
b/xen/arch/arm/arm64/debug-pl011.inc
index 6d60e78c8ba3..80eb8fdc1ec7 100644
--- a/xen/arch/arm/arm64/debug-pl011.inc
+++ b/xen/arch/arm/arm64/debug-pl011.inc
@@ -25,9 +25,9 @@
*/
.macro early_uart_init xb, c
mov x\c, #(7372800 / CONFIG_EARLY_UART_PL011_BAUD_RATE % 16)
- strh w\c, [\xb, #FBRD] /* -> UARTFBRD (Baud divisor fraction) */
+ str w\c, [\xb, #FBRD] /* -> UARTFBRD (Baud divisor fraction) */
mov x\c, #(7372800 / CONFIG_EARLY_UART_PL011_BAUD_RATE / 16)
- strh w\c, [\xb, #IBRD] /* -> UARTIBRD (Baud divisor integer) */
+ str w\c, [\xb, #IBRD] /* -> UARTIBRD (Baud divisor integer) */
mov x\c, #WLEN_8 /* 8n1 */
str w\c, [\xb, #LCR_H] /* -> UARTLCR_H (Line control) */
ldr x\c, =(RXE | TXE | UARTEN)
@@ -41,7 +41,7 @@
*/
.macro early_uart_ready xb, c
1:
- ldrh w\c, [\xb, #FR] /* <- UARTFR (Flag register) */
+ ldr w\c, [\xb, #FR] /* <- UARTFR (Flag register) */
tst w\c, #BUSY /* Check BUSY bit */
b.ne 1b /* Wait for the UART to be ready */
.endm
@@ -52,7 +52,7 @@
* wt: register which contains the character to transmit
*/
.macro early_uart_transmit xb, wt
- strb \wt, [\xb, #DR] /* -> UARTDR (Data Register) */
+ str \wt, [\xb, #DR] /* -> UARTDR (Data Register) */
.endm
/*
--
2.25.1
