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Re: [PATCH] ibex_uart: fix XOR-as-pow
From: |
Eric Blake |
Subject: |
Re: [PATCH] ibex_uart: fix XOR-as-pow |
Date: |
Tue, 23 Jun 2020 15:07:01 -0500 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 |
On 6/23/20 2:54 PM, Paolo Bonzini wrote:
The xor-as-pow warning in clang actually detected a genuine bug.
Fix it.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
hw/char/ibex_uart.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/char/ibex_uart.c b/hw/char/ibex_uart.c
index 3e0dd9968e..45cd724998 100644
--- a/hw/char/ibex_uart.c
+++ b/hw/char/ibex_uart.c
@@ -331,7 +331,7 @@ static void ibex_uart_write(void *opaque, hwaddr addr,
if (value & UART_CTRL_NCO) {
uint64_t baud = ((value & UART_CTRL_NCO) >> 16);
baud *= 1000;
- baud /= 2 ^ 20;
+ baud >>= 20;
Dividing by 1M instead of 22 seems much more logical, indeed :)
It's odd that we are scaling up by 1000, down by 1024*1024, then
s->char_tx_time = (NANOSECONDS_PER_SECOND / baud) * 10;
inverting and scaling by 10. I don't know if there is a more succinct
way to write the intended transformation.
}
But even without reading the hardware manual to see if the resulting
scaling is correct, the typo fix is obvious enough to give:
Reviewed-by: Eric Blake <eblake@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
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