linux-kernel - [PATCH 1/6] Revert "serial/8250_pci: init-quirk msi support for kt serial controller"

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Date:	Fri, 06 Apr 2012 11:49:37 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	gregkh@...uxfoundation.org
Cc:	Sudhakar Mamillapalli <sudhakar@...com>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	linux-serial@...r.kernel.org, Nhan H Mai <nhan.h.mai@...el.com>,
	Alan Cox <alan@...ux.intel.com>
Subject: [PATCH 1/6] Revert "serial/8250_pci: init-quirk msi support for kt
 serial controller"

This reverts commit e86ff4a63c9fdd875ba8492577cd1ad2252f525c.

This tried to enforce the semantics of one interrupt per iir read of the
THRE (transmit-hold empty) status, but events from other sources
(particularly modem status) defeat this guarantee.

This change also broke 8250_pci suspend/resume support as
pciserial_resume_ports() re-runs .init() quirks, but does not run
.exit() quirks in pciserial_suspend_ports() leading to reports like:

  sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:16.3/msi_irqs'

...and a subsequent crash.  The mismatch of init/exit at suspend/resume
seems like a bug in its own right.

[stable: 3.3.x]
Cc: <stable@...r.kernel.org>
Cc: Alan Cox <alan@...ux.intel.com>
Cc: Sudhakar Mamillapalli <sudhakar@...com>
Reported-by: Nhan H Mai <nhan.h.mai@...el.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
 drivers/tty/serial/8250/8250_pci.c |   14 --------------
 1 files changed, 0 insertions(+), 14 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index da2b0b0..1d4ccf8 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1118,18 +1118,6 @@ pci_xr17c154_setup(struct serial_private *priv,
 	return pci_default_setup(priv, board, port, idx);
 }
 
-static int try_enable_msi(struct pci_dev *dev)
-{
-	/* use msi if available, but fallback to legacy otherwise */
-	pci_enable_msi(dev);
-	return 0;
-}
-
-static void disable_msi(struct pci_dev *dev)
-{
-	pci_disable_msi(dev);
-}
-
 #define PCI_VENDOR_ID_SBSMODULARIO	0x124B
 #define PCI_SUBVENDOR_ID_SBSMODULARIO	0x124B
 #define PCI_DEVICE_ID_OCTPRO		0x0001
@@ -1249,9 +1237,7 @@ static struct pci_serial_quirk pci_serial_quirks[] __refdata = {
 		.device		= PCI_DEVICE_ID_INTEL_PATSBURG_KT,
 		.subvendor	= PCI_ANY_ID,
 		.subdevice	= PCI_ANY_ID,
-		.init		= try_enable_msi,
 		.setup		= kt_serial_setup,
-		.exit		= disable_msi,
 	},
 	/*
 	 * ITE

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