Hi Michal, > On 1 Jun 2023, at 10:50, Michal Orzel <michal.or...@amd.com> wrote: > > 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) */
Is it really ok to drop the 8bit access here ? Regards Bertrand > .endm > > /* > -- > 2.25.1 >
