serial: 8250_pci: Correct uartclk for xr17v35x expansion chips

The internal clock of the master chip, which is usually 125MHz, is only half
(62.5MHz) for the slave chips. So we have to adjust the uartclk for all the
slave ports. Therefor we add a new function to determine if a slave chip is
present and update pci_xr17v35x_setup accordingly.

Signed-off-by: Soeren Grunewald <soeren.grunewald@desy.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 1541554262df836f9d63d3461cfd85ee9ce7a991..e55f18b93fe7e7334dce31ebab7e43aac1ad493e 100644 (file)
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1823,6 +1823,9 @@ static int pci_eg20t_init(struct pci_dev *dev)
 #endif
 }
 
+#define PCI_DEVICE_ID_EXAR_XR17V4358   0x4358
+#define PCI_DEVICE_ID_EXAR_XR17V8358   0x8358
+
 static int
 pci_xr17c154_setup(struct serial_private *priv,
                  const struct pciserial_board *board,
@@ -1832,6 +1835,15 @@ pci_xr17c154_setup(struct serial_private *priv,
        return pci_default_setup(priv, board, port, idx);
 }
 
+static inline int
+xr17v35x_has_slave(struct serial_private *priv)
+{
+       const int dev_id = priv->dev->device;
+
+       return ((dev_id == PCI_DEVICE_ID_EXAR_XR17V4358) ||
+               (dev_id == PCI_DEVICE_ID_EXAR_XR17V8358));
+}
+
 static int
 pci_xr17v35x_setup(struct serial_private *priv,
                  const struct pciserial_board *board,
@@ -1845,6 +1857,13 @@ pci_xr17v35x_setup(struct serial_private *priv,
 
        port->port.flags |= UPF_EXAR_EFR;
 
+       /*
+        * Setup the uart clock for the devices on expansion slot to
+        * half the clock speed of the main chip (which is 125MHz)
+        */
+       if (xr17v35x_has_slave(priv) && idx >= 8)
+               port->port.uartclk = (7812500 * 16 / 2);
+
        /*
         * Setup Multipurpose Input/Output pins.
         */
@@ -1998,9 +2017,6 @@ pci_wch_ch38x_setup(struct serial_private *priv,
 #define PCIE_DEVICE_ID_WCH_CH382_2S1P  0x3250
 #define PCIE_DEVICE_ID_WCH_CH384_4S    0x3470
 
-#define PCI_DEVICE_ID_EXAR_XR17V4358   0x4358
-#define PCI_DEVICE_ID_EXAR_XR17V8358   0x8358
-
 /* Unknown vendors/cards - this should not be in linux/pci_ids.h */
 #define PCI_SUBDEVICE_ID_UNKNOWN_0x1584        0x1584
 #define PCI_SUBDEVICE_ID_UNKNOWN_0x1588        0x1588