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From f1be0b62a03b90a40a03e21f965e4cbb89809bb1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?=
<marmarek@invisiblethingslab.com>
Date: Tue, 7 Jun 2022 14:07:34 +0200
Subject: [PATCH 20/51] ns16550: use poll mode if INTERRUPT_LINE is 0xff
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Intel LPSS has INTERRUPT_LINE set to 0xff by default, that is declared
by the PCI Local Bus Specification Revision 3.0 (from 2004) as
"unknown"/"no connection". Fallback to poll mode in this case.
The 0xff handling is x86-specific, the surrounding code is guarded with
CONFIG_X86 anyway.
Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
master commit: 6a2ea1a2370a0c8a0210accac0ae62e68c185134
master date: 2022-05-20 12:19:45 +0200
---
xen/drivers/char/ns16550.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
index 30596d60d4ed..2d2bd2a02469 100644
--- a/xen/drivers/char/ns16550.c
+++ b/xen/drivers/char/ns16550.c
@@ -1221,6 +1221,19 @@ pci_uart_config(struct ns16550 *uart, bool_t skip_amt, unsigned int idx)
pci_conf_read8(PCI_SBDF(0, b, d, f),
PCI_INTERRUPT_LINE) : 0;
+#ifdef CONFIG_X86
+ /*
+ * PCI Local Bus Specification Revision 3.0 defines 0xff value
+ * as special only for X86.
+ */
+ if ( uart->irq == 0xff )
+ uart->irq = 0;
+#endif
+ if ( !uart->irq )
+ printk(XENLOG_INFO
+ "ns16550: %pp: no legacy IRQ, using poll mode\n",
+ &PCI_SBDF(0, b, d, f));
+
return 0;
}
}
--
2.35.1
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