[PATCH 5.16 0666/1017] serial: 8250_lpss: Balance reference count for PCI DMA device

Greg Kroah-Hartman
2022-04-05T13:24:20Z

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

[ Upstream commit 5318f70da7e82649d794fc27d8a127c22aa3566e ]

The pci_get_slot() increases its reference count, the caller
must decrement the reference count by calling pci_dev_put().

Fixes: 9a1870ce812e ("serial: 8250: don't use slave_id of dma_slave_config")
Depends-on: a13e19cf3dc1 ("serial: 8250_lpss: split LPSS driver to separate module")
Reported-by: Qing Wang <wangqing@vivo.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220223151240.70248-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/serial/8250/8250_lpss.c | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_lpss.c b/drivers/tty/serial/8250/8250_lpss.c
index d3bafec7619d..0f5af061e0b4 100644
--- a/drivers/tty/serial/8250/8250_lpss.c
+++ b/drivers/tty/serial/8250/8250_lpss.c
@@ -117,8 +117,7 @@ static int byt_serial_setup(struct lpss8250 *lpss, struct uart_port *port)
{
struct dw_dma_slave *param = &lpss->dma_param;
struct pci_dev *pdev = to_pci_dev(port->dev);
- unsigned int dma_devfn = PCI_DEVFN(PCI_SLOT(pdev->devfn), 0);
- struct pci_dev *dma_dev = pci_get_slot(pdev->bus, dma_devfn);
+ struct pci_dev *dma_dev;

switch (pdev->device) {
case PCI_DEVICE_ID_INTEL_BYT_UART1:
@@ -137,6 +136,8 @@ static int byt_serial_setup(struct lpss8250 *lpss, struct uart_port *port)
return -EINVAL;
}

+ dma_dev = pci_get_slot(pdev->bus, PCI_DEVFN(PCI_SLOT(pdev->devfn), 0));
+
param->dma_dev = &dma_dev->dev;
param->m_master = 0;
param->p_master = 1;
@@ -152,6 +153,14 @@ static int byt_serial_setup(struct lpss8250 *lpss, struct uart_port *port)
return 0;
}

+static void byt_serial_exit(struct lpss8250 *lpss)
+{
+ struct dw_dma_slave *param = &lpss->dma_param;
+
+ /* Paired with pci_get_slot() in the byt_serial_setup() above */
+ put_device(param->dma_dev);
+}
+
static int ehl_serial_setup(struct lpss8250 *lpss, struct uart_port *port)
{
struct uart_8250_dma *dma = &lpss->data.dma;
@@ -170,6 +179,13 @@ static int ehl_serial_setup(struct lpss8250 *lpss, struct uart_port *port)
return 0;
}

+static void ehl_serial_exit(struct lpss8250 *lpss)
+{
+ struct uart_8250_port *up = serial8250_get_port(lpss->data.line);
+
+ up->dma = NULL;
+}
+
#ifdef CONFIG_SERIAL_8250_DMA
static const struct dw_dma_platform_data qrk_serial_dma_pdata = {
.nr_channels = 2,
@@ -344,8 +360,7 @@ static int lpss8250_probe(struct pci_dev *pdev, const struct pci_device_id *id)
return 0;

err_exit:
- if (lpss->board->exit)
- lpss->board->exit(lpss);
+ lpss->board->exit(lpss);
pci_free_irq_vectors(pdev);
return ret;
}
@@ -356,8 +371,7 @@ static void lpss8250_remove(struct pci_dev *pdev)

serial8250_unregister_port(lpss->data.line);

- if (lpss->board->exit)
- lpss->board->exit(lpss);
+ lpss->board->exit(lpss);
pci_free_irq_vectors(pdev);
}

@@ -365,12 +379,14 @@ static const struct lpss8250_board byt_board = {
.freq = 100000000,
.base_baud = 2764800,
.setup = byt_serial_setup,
+ .exit = byt_serial_exit,
};

static const struct lpss8250_board ehl_board = {
.freq = 200000000,
.base_baud = 12500000,
.setup = ehl_serial_setup,
+ .exit = ehl_serial_exit,
};

static const struct lpss8250_board qrk_board = {
--
2.34.1