From: Hans Verkuil hverkuil-cisco@xs4all.nl
stable inclusion from linux-4.19.198 commit c93a0890e9551698f24553381c44dafd6c90275b
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[ 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 Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/media/pci/cobalt/cobalt-driver.c | 1 + drivers/media/pci/cobalt/cobalt-driver.h | 7 ++++++- 2 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/media/pci/cobalt/cobalt-driver.c b/drivers/media/pci/cobalt/cobalt-driver.c index 4885e833c0522..f422558e63920 100644 --- a/drivers/media/pci/cobalt/cobalt-driver.c +++ b/drivers/media/pci/cobalt/cobalt-driver.c @@ -675,6 +675,7 @@ 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 429bee4ef79c5..883093e5adea9 100644 --- a/drivers/media/pci/cobalt/cobalt-driver.h +++ b/drivers/media/pci/cobalt/cobalt-driver.h @@ -250,6 +250,8 @@ 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;
@@ -319,10 +321,13 @@ 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)