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From d6da3c31a2b00b3db5462ffef7c389977416f280 Mon Sep 17 00:00:00 2001
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Message-Id: <d6da3c31a2b00b3db5462ffef7c389977416f280.1429703426.git.panand@redhat.com>
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In-Reply-To: <de1db775d6e9b51f014442677863b57b8566c510.1429703426.git.panand@redhat.com>
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References: <de1db775d6e9b51f014442677863b57b8566c510.1429703426.git.panand@redhat.com>
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From: Pratyush Anand <panand@redhat.com>
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Date: Thu, 16 Apr 2015 14:00:03 +0530
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Subject: [PATCH 15/15] arm64: wait for transmit completion before next
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character transmission
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Previous transmission must be completed before next character to be
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transmitted, otherwise TX buffer may saturate and we will not see all
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the characters on screen.
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Signed-off-by: Pratyush Anand <panand@redhat.com>
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---
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purgatory/arch/arm64/purgatory-arm64.c | 24 +++++++++++++++++++++++-
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1 file changed, 23 insertions(+), 1 deletion(-)
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diff --git a/purgatory/arch/arm64/purgatory-arm64.c b/purgatory/arch/arm64/purgatory-arm64.c
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index 25960c30bd05..3a1c9243bfa2 100644
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--- a/purgatory/arch/arm64/purgatory-arm64.c
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+++ b/purgatory/arch/arm64/purgatory-arm64.c
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@@ -11,15 +11,37 @@ extern uint32_t *arm64_sink;
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extern void (*arm64_kernel_entry)(uint64_t);
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extern uint64_t arm64_dtb_addr;
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+static void wait_for_xmit_complete(void)
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+{
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+ volatile uint32_t status;
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+ volatile uint32_t *status_reg;
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+
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+ /*
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+ * Since most of the UART with ARM platform has LSR register at
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+ * offset 0x14 and should have value as 0x60 for TX empty, so we
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+ * have hardcoded these values. Can modify in future if need
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+ * arises.
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+ */
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+ status_reg = (volatile uint32_t *)((uint64_t)arm64_sink + 0x14);
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+ while (1) {
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+ status = *status_reg;
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+ if ((status & 0x60) == 0x60)
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+ break;
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+ }
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+}
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+
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void putchar(int ch)
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{
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if (!arm64_sink)
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return;
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+ wait_for_xmit_complete();
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*arm64_sink = ch;
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- if (ch == '\n')
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+ if (ch == '\n') {
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+ wait_for_xmit_complete();
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*arm64_sink = '\r';
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+ }
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}
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void setup_arch(void)
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--
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2.1.0
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