linux-kernel - [PATCH v2] tty: serial: 8250: Fix port count mismatch with the device

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Date: Mon, 17 Jun 2024 14:30:58 +0800
From: Crescent Hsieh <crescentcy.hsieh@...a.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Andy Shevchenko <andy.shevchenko@...il.com>
Cc: linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org,
	Crescent Hsieh <crescentcy.hsieh@...a.com>
Subject: [PATCH v2] tty: serial: 8250: Fix port count mismatch with the device

Normally, the number of ports is indicated by the third digit of the
device ID on Moxa PCI serial boards. For example, `0x1121` indicates a
device with 2 ports.

However, `CP116E_A_A` and `CP116E_A_B` are exceptions; they have 8
ports, but the third digit of the device ID is `6`.

This patch introduces a function to retrieve the number of ports on Moxa
PCI serial boards, addressing the issue described above.

Fixes: 37058fd5d239 ("tty: serial: 8250: Add support for MOXA Mini PCIe boards")
Signed-off-by: Crescent Hsieh <crescentcy.hsieh@...a.com>

---
Changes from v1 to v2:
- Add the "Fixes" tag correctly

v1: https://lore.kernel.org/all/20240614090322.2303-1-crescentcy.hsieh@moxa.com/

---
 drivers/tty/serial/8250/8250_pci.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
index 40af74b55933..e1d7aa2fa347 100644
--- a/drivers/tty/serial/8250/8250_pci.c
+++ b/drivers/tty/serial/8250/8250_pci.c
@@ -1985,6 +1985,17 @@ enum {
 	MOXA_SUPP_RS485 = BIT(2),
 };
 
+static unsigned short moxa_get_nports(unsigned short device)
+{
+	switch (device) {
+	case PCI_DEVICE_ID_MOXA_CP116E_A_A:
+	case PCI_DEVICE_ID_MOXA_CP116E_A_B:
+		return 8;
+	}
+
+	return FIELD_GET(0x00F0, device);
+}
+
 static bool pci_moxa_is_mini_pcie(unsigned short device)
 {
 	if (device == PCI_DEVICE_ID_MOXA_CP102N	||
@@ -2038,7 +2049,7 @@ static int pci_moxa_init(struct pci_dev *dev)
 {
 	unsigned short device = dev->device;
 	resource_size_t iobar_addr = pci_resource_start(dev, 2);
-	unsigned int num_ports = (device & 0x00F0) >> 4, i;
+	unsigned int i, num_ports = moxa_get_nports(device);
 	u8 val, init_mode = MOXA_RS232;
 
 	if (!(pci_moxa_supported_rs(dev) & MOXA_SUPP_RS232)) {
-- 
2.34.1