media: cobalt: fix race condition in setting HPD

[ Upstream commit 3d37ef41bed0854805ab9af22c422267510e1344 ]

The cobalt_s_bit_sysctrl reads the old register value over PCI,
then changes a bit and sets writes the new value to the register.

This is used among other things for setting the HPD output pin.

But if the HPD is changed for multiple inputs at the same time,
then this causes a race condition where a stale value is read.

Serialize this function with a mutex.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/media/pci/cobalt/cobalt-driver.c b/drivers/media/pci/cobalt/cobalt-driver.c
index 0695078ef81252c37eb12fa966d1c91d627279b5..1bd8bbe57a30e6ccd2c2dc66aea24ef2fc46665e 100644 (file)
--- a/drivers/media/pci/cobalt/cobalt-driver.c
+++ b/drivers/media/pci/cobalt/cobalt-driver.c
@@ -667,6 +667,7 @@ static int cobalt_probe(struct pci_dev *pci_dev,
                return -ENOMEM;
        cobalt->pci_dev = pci_dev;
        cobalt->instance = i;
+       mutex_init(&cobalt->pci_lock);
 
        retval = v4l2_device_register(&pci_dev->dev, &cobalt->v4l2_dev);
        if (retval) {

diff --git a/drivers/media/pci/cobalt/cobalt-driver.h b/drivers/media/pci/cobalt/cobalt-driver.h
index bca68572b3242af74527cfc39f3c67fd6f104721..12c33e035904cac536b55968927a992e0f850066 100644 (file)
--- a/drivers/media/pci/cobalt/cobalt-driver.h
+++ b/drivers/media/pci/cobalt/cobalt-driver.h
@@ -251,6 +251,8 @@ struct cobalt {
        int instance;
        struct pci_dev *pci_dev;
        struct v4l2_device v4l2_dev;
+       /* serialize PCI access in cobalt_s_bit_sysctrl() */
+       struct mutex pci_lock;
 
        void __iomem *bar0, *bar1;
 
@@ -320,10 +322,13 @@ static inline u32 cobalt_g_sysctrl(struct cobalt *cobalt)
 static inline void cobalt_s_bit_sysctrl(struct cobalt *cobalt,
                                        int bit, int val)
 {
-       u32 ctrl = cobalt_read_bar1(cobalt, COBALT_SYS_CTRL_BASE);
+       u32 ctrl;
 
+       mutex_lock(&cobalt->pci_lock);
+       ctrl = cobalt_read_bar1(cobalt, COBALT_SYS_CTRL_BASE);
        cobalt_write_bar1(cobalt, COBALT_SYS_CTRL_BASE,
                        (ctrl & ~(1UL << bit)) | (val << bit));
+       mutex_unlock(&cobalt->pci_lock);
 }
 
 static inline u32 cobalt_g_sysstat(struct cobalt *cobalt)