serial: 8250_lpss: Balance reference count for PCI DMA device

BugLink: https://bugs.launchpad.net/bugs/1969110
[ 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>
(cherry picked from commit b59173ff16fbfa94223457cc97cce943867a27db)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/drivers/tty/serial/8250/8250_lpss.c b/drivers/tty/serial/8250/8250_lpss.c
index 848d81e3838c24baf87727fee78948b08ae4c9a7..49ae73f4d3a04141f99bbd538ff7f0c9df19630c 100644 (file)
--- a/drivers/tty/serial/8250/8250_lpss.c
+++ b/drivers/tty/serial/8250/8250_lpss.c
@@ -121,8 +121,7 @@ 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:
@@ -141,6 +140,8 @@ 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;
@@ -156,6 +157,14 @@ 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;
@@ -171,6 +180,13 @@ 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,
@@ -345,8 +361,7 @@ 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;
 }
@@ -357,8 +372,7 @@ 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);
 }
 
@@ -366,12 +380,14 @@ 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 = {