Commit b6adea33 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab Committed by Linus Torvalds

8250: fix boot hang with serial console when using with Serial Over Lan port

Intel 8257x Ethernet boards have a feature called Serial Over Lan.

This feature works by emulating a serial port, and it is detected by
kernel as a normal 8250 port.  However, this emulation is not perfect, as
also noticed on changeset 7500b1f6.

Before this patch, the kernel were trying to check if the serial TX is
capable of work using IRQ's.

This were done with a code similar this:

        serial_outp(up, UART_IER, UART_IER_THRI);
        lsr = serial_in(up, UART_LSR);
        iir = serial_in(up, UART_IIR);
        serial_outp(up, UART_IER, 0);

        if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT)
		up->bugs |= UART_BUG_TXEN;

This works fine for other 8250 ports, but, on 8250-emulated SoL port, the
chip is a little lazy to down UART_IIR_NO_INT at UART_IIR register.

Due to that, UART_BUG_TXEN is sometimes enabled.  However, as TX IRQ keeps
working, and the TX polling is now enabled, the driver miss-interprets the
IRQ received later, hanging up the machine until a key is pressed at the
serial console.

This is the 6 version of this patch.  Previous versions were trying to
introduce a large enough delay between serial_outp and serial_in(up,
UART_IIR), but not taking forever.  However, the needed delay couldn't be
safely determined.

At the experimental tests, a delay of 1us solves most of the cases, but
still hangs sometimes.  Increasing the delay to 5us was better, but still
doesn't solve.  A very high delay of 50 ms seemed to work every time.

However, poking around with delays and pray for it to be enough doesn't
seem to be a good approach, even for a quirk.

So, instead of playing with random large arbitrary delays, let's just
disable UART_BUG_TXEN for all SoL ports.

[akpm@linux-foundation.org: fix warnings]
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: <stable@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3cf31140
...@@ -2083,6 +2083,20 @@ static int serial8250_startup(struct uart_port *port) ...@@ -2083,6 +2083,20 @@ static int serial8250_startup(struct uart_port *port)
serial8250_set_mctrl(&up->port, up->port.mctrl); serial8250_set_mctrl(&up->port, up->port.mctrl);
/* Serial over Lan (SoL) hack:
Intel 8257x Gigabit ethernet chips have a
16550 emulation, to be used for Serial Over Lan.
Those chips take a longer time than a normal
serial device to signalize that a transmission
data was queued. Due to that, the above test generally
fails. One solution would be to delay the reading of
iir. However, this is not reliable, since the timeout
is variable. So, let's just don't test if we receive
TX irq. This way, we'll never enable UART_BUG_TXEN.
*/
if (up->port.flags & UPF_NO_TXEN_TEST)
goto dont_test_tx_en;
/* /*
* Do a quick test to see if we receive an * Do a quick test to see if we receive an
* interrupt when we enable the TX irq. * interrupt when we enable the TX irq.
...@@ -2102,6 +2116,7 @@ static int serial8250_startup(struct uart_port *port) ...@@ -2102,6 +2116,7 @@ static int serial8250_startup(struct uart_port *port)
up->bugs &= ~UART_BUG_TXEN; up->bugs &= ~UART_BUG_TXEN;
} }
dont_test_tx_en:
spin_unlock_irqrestore(&up->port.lock, flags); spin_unlock_irqrestore(&up->port.lock, flags);
/* /*
......
...@@ -798,6 +798,21 @@ pci_default_setup(struct serial_private *priv, ...@@ -798,6 +798,21 @@ pci_default_setup(struct serial_private *priv,
return setup_port(priv, port, bar, offset, board->reg_shift); return setup_port(priv, port, bar, offset, board->reg_shift);
} }
static int skip_tx_en_setup(struct serial_private *priv,
const struct pciserial_board *board,
struct uart_port *port, int idx)
{
port->flags |= UPF_NO_TXEN_TEST;
printk(KERN_DEBUG "serial8250: skipping TxEn test for device "
"[%04x:%04x] subsystem [%04x:%04x]\n",
priv->dev->vendor,
priv->dev->device,
priv->dev->subsystem_vendor,
priv->dev->subsystem_device);
return pci_default_setup(priv, board, port, idx);
}
/* This should be in linux/pci_ids.h */ /* This should be in linux/pci_ids.h */
#define PCI_VENDOR_ID_SBSMODULARIO 0x124B #define PCI_VENDOR_ID_SBSMODULARIO 0x124B
#define PCI_SUBVENDOR_ID_SBSMODULARIO 0x124B #define PCI_SUBVENDOR_ID_SBSMODULARIO 0x124B
...@@ -864,6 +879,27 @@ static struct pci_serial_quirk pci_serial_quirks[] __refdata = { ...@@ -864,6 +879,27 @@ static struct pci_serial_quirk pci_serial_quirks[] __refdata = {
.init = pci_inteli960ni_init, .init = pci_inteli960ni_init,
.setup = pci_default_setup, .setup = pci_default_setup,
}, },
{
.vendor = PCI_VENDOR_ID_INTEL,
.device = PCI_DEVICE_ID_INTEL_8257X_SOL,
.subvendor = PCI_ANY_ID,
.subdevice = PCI_ANY_ID,
.setup = skip_tx_en_setup,
},
{
.vendor = PCI_VENDOR_ID_INTEL,
.device = PCI_DEVICE_ID_INTEL_82573L_SOL,
.subvendor = PCI_ANY_ID,
.subdevice = PCI_ANY_ID,
.setup = skip_tx_en_setup,
},
{
.vendor = PCI_VENDOR_ID_INTEL,
.device = PCI_DEVICE_ID_INTEL_82573E_SOL,
.subvendor = PCI_ANY_ID,
.subdevice = PCI_ANY_ID,
.setup = skip_tx_en_setup,
},
/* /*
* ITE * ITE
*/ */
......
...@@ -2323,6 +2323,9 @@ ...@@ -2323,6 +2323,9 @@
#define PCI_DEVICE_ID_INTEL_82378 0x0484 #define PCI_DEVICE_ID_INTEL_82378 0x0484
#define PCI_DEVICE_ID_INTEL_I960 0x0960 #define PCI_DEVICE_ID_INTEL_I960 0x0960
#define PCI_DEVICE_ID_INTEL_I960RM 0x0962 #define PCI_DEVICE_ID_INTEL_I960RM 0x0962
#define PCI_DEVICE_ID_INTEL_8257X_SOL 0x1062
#define PCI_DEVICE_ID_INTEL_82573E_SOL 0x1085
#define PCI_DEVICE_ID_INTEL_82573L_SOL 0x108F
#define PCI_DEVICE_ID_INTEL_82815_MC 0x1130 #define PCI_DEVICE_ID_INTEL_82815_MC 0x1130
#define PCI_DEVICE_ID_INTEL_82815_CGC 0x1132 #define PCI_DEVICE_ID_INTEL_82815_CGC 0x1132
#define PCI_DEVICE_ID_INTEL_82092AA_0 0x1221 #define PCI_DEVICE_ID_INTEL_82092AA_0 0x1221
......
...@@ -296,6 +296,7 @@ struct uart_port { ...@@ -296,6 +296,7 @@ struct uart_port {
#define UPF_HARDPPS_CD ((__force upf_t) (1 << 11)) #define UPF_HARDPPS_CD ((__force upf_t) (1 << 11))
#define UPF_LOW_LATENCY ((__force upf_t) (1 << 13)) #define UPF_LOW_LATENCY ((__force upf_t) (1 << 13))
#define UPF_BUGGY_UART ((__force upf_t) (1 << 14)) #define UPF_BUGGY_UART ((__force upf_t) (1 << 14))
#define UPF_NO_TXEN_TEST ((__force upf_t) (1 << 15))
#define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 << 16)) #define UPF_MAGIC_MULTIPLIER ((__force upf_t) (1 << 16))
#define UPF_CONS_FLOW ((__force upf_t) (1 << 23)) #define UPF_CONS_FLOW ((__force upf_t) (1 << 23))
#define UPF_SHARE_IRQ ((__force upf_t) (1 << 24)) #define UPF_SHARE_IRQ ((__force upf_t) (1 << 24))
......
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