linux-kernel - [PATCH 4.4 48/58] [media] media: solo6x10: fix lockup by avoiding delayed register write

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Message-Id: <20170106213908.765389565@linuxfoundation.org>
Date:   Fri,  6 Jan 2017 22:44:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Andrey Utkin <andrey.utkin@...p.bluecherry.net>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>
Subject: [PATCH 4.4 48/58] [media] media: solo6x10: fix lockup by avoiding delayed register write

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrey Utkin <andrey.utkin@...p.bluecherry.net>

commit 5fc4b067ec082c3127e0156f800769b7e0dce078 upstream.

This fixes a lockup at device probing which happens on some solo6010
hardware samples. This is a regression introduced by commit e1ceb25a1569
("[media] SOLO6x10: remove unneeded register locking and barriers")

The observed lockup happens in solo_set_motion_threshold() called from
solo_motion_config().

This extra "flushing" is not fundamentally needed for every write, but
apparently the code in driver assumes such behaviour at last in some
places.

Actual fix was proposed by Hans Verkuil.

Fixes: e1ceb25a1569 ("[media] SOLO6x10: remove unneeded register locking and barriers")

Signed-off-by: Andrey Utkin <andrey.utkin@...p.bluecherry.net>
Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/media/pci/solo6x10/solo6x10.h |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/media/pci/solo6x10/solo6x10.h
+++ b/drivers/media/pci/solo6x10/solo6x10.h
@@ -286,7 +286,10 @@ static inline u32 solo_reg_read(struct s
 static inline void solo_reg_write(struct solo_dev *solo_dev, int reg,
 				  u32 data)
 {
+	u16 val;
+
 	writel(data, solo_dev->reg_base + reg);
+	pci_read_config_word(solo_dev->pdev, PCI_STATUS, &val);
 }
 
 static inline void solo_irq_on(struct solo_dev *dev, u32 mask)