Previous transmission must be completed before next character to be
transmitted, otherwise TX buffer may saturate and we will not see all
the characters on screen.
Signed-off-by: Pratyush Anand <panand at redhat.com>
---
purgatory/arch/arm64/purgatory-arm64.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/purgatory/arch/arm64/purgatory-arm64.c b/purgatory/arch/arm64/purgatory-arm64.c
index 25960c30bd05..3a1c9243bfa2 100644
--- a/purgatory/arch/arm64/purgatory-arm64.c
+++ b/purgatory/arch/arm64/purgatory-arm64.c
@@ -11,15 +11,37 @@ extern uint32_t *arm64_sink;
extern void (*arm64_kernel_entry)(uint64_t);
extern uint64_t arm64_dtb_addr;
+static void wait_for_xmit_complete(void)
+{
+ volatile uint32_t status;
+ volatile uint32_t *status_reg;
+
+ /*
+ * Since most of the UART with ARM platform has LSR register at
+ * offset 0x14 and should have value as 0x60 for TX empty, so we
+ * have hardcoded these values. Can modify in future if need
+ * arises.
+ */
+ status_reg = (volatile uint32_t *)((uint64_t)arm64_sink + 0x14);
+ while (1) {
+ status = *status_reg;
+ if ((status & 0x60) == 0x60)
+ break;
+ }
+}
+
void putchar(int ch)
{
if (!arm64_sink)
return;
+ wait_for_xmit_complete();
*arm64_sink = ch;
- if (ch == '\n')
+ if (ch == '\n') {
+ wait_for_xmit_complete();
*arm64_sink = '\r';
+ }
}
void setup_arch(void)
--
2.1.0
