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Date: Mon, 25 Aug 2014 08:18:25 -0400
From: Peter Hurley <peter@...leysoftware.com>
To: Scott Yuan <scottzero0@...il.com>, gregkh@...uxfoundation.org,
robh@...nel.org
CC: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] 8250: serial device file is out of order
Hi Scott,
On 08/25/2014 07:38 AM, Scott Yuan wrote:
> From ebb85a61456bf25f87aeb8a31c92c74540bdf306 Mon Sep 17 00:00:00 2001
> From: Scott Yuan <scottzero0@...il.com>
> Date: Sun, 24 Aug 2014 13:46:56 +0800
> Subject: [PATCH] 8250: serial device file is out of order
>
> On x86 architecture, the configuration of serial device maybe get from ACPI
> DSDT, but the order of DSDT is not mandatory, result as array serial8250_ports
> is out of order. This situation is more obvious in multiple serial port
> mainboard. Sort it by unique id that in DSDT will fix it.
Why does this matter?
>
> Signed-off-by: Scott Yuan <scottzero0@...il.com>
> ---
> drivers/pnp/pnpacpi/core.c | 1 +
> drivers/tty/serial/8250/8250_core.c | 40 ++++++++++++++++++++++++++++++++++++-
> drivers/tty/serial/8250/8250_pnp.c | 12 +++++++++++
> include/linux/pnp.h | 1 +
> include/linux/serial_8250.h | 2 ++
> 5 files changed, 55 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pnp/pnpacpi/core.c b/drivers/pnp/pnpacpi/core.c
> index a5c6cb7..84b518e 100644
> --- a/drivers/pnp/pnpacpi/core.c
> +++ b/drivers/pnp/pnpacpi/core.c
> @@ -254,6 +254,7 @@ static int __init pnpacpi_add_device(struct acpi_device *device)
> return -ENOMEM;
> dev->data = device;
> + dev->is_acpi = 1;
> /* .enabled means the device can decode the resources */
> dev->active = device->status.enabled;
> if (acpi_has_method(device->handle, "_SRS"))
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index 7a91c6d..0e5ece5 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -3221,6 +3221,41 @@ static struct uart_8250_port *serial8250_find_match_or_unused(struct uart_port *
> return NULL;
> }
> +static struct uart_8250_port *
> +serial8250_find_match_sorted_port(struct uart_port *port)
> +{
> + int i, j;
> + struct uart_8250_port *uart;
> +
> + uart = container_of(port, struct uart_8250_port, port);
> +
> + /*
> + * We need sorted array serial8250_ports, it is sort by ACPI
> + * device unique id, so find an apropriate position to insert.
> + */
> + for (i = 0; i < nr_uarts; i++) {
> + if (serial8250_ports[i].uid == 0 ||
> + uart->uid < serial8250_ports[i].uid)
> + break;
> + }
> +
> + /*
> + * If current uid that in serial8250_ports is big than port uid,
> + * then move 8250 port data.
> + */
The port index cannot be changed after the port is registered with the
tty core. That's because the tty core associates the index at registration
time with a specific tty.
Also, this is thread-unsafe: the 8250 driver uses serial_mutex to
protect concurrent add/remove to the serial8250_ports but otherwise
does not claim that mutex to dereference that table once a given port
index has been assigned.
> + if (i < nr_uarts - 1 &&
> + uart->uid < serial8250_ports[i].uid) {
> + memmove(&serial8250_ports[i+1], &serial8250_ports[i],
> + (nr_uarts - i - 1) * sizeof(struct uart_8250_port));
> +
> + /* modify port.line, since data moved */
> + for (j = i + 1; j < nr_uarts; j++)
> + serial8250_ports[j].port.line += 1;
> + }
> + serial8250_ports[i].uid = uart->uid;
> + return &serial8250_ports[i];
> +}
> +
> /**
> * serial8250_register_8250_port - register a serial port
> * @up: serial port template
> @@ -3244,7 +3279,10 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
> mutex_lock(&serial_mutex);
> - uart = serial8250_find_match_or_unused(&up->port);
> + if (up->is_acpi)
> + uart = serial8250_find_match_sorted_port(&up->port);
> + else
> + uart = serial8250_find_match_or_unused(&up->port);
> if (uart && uart->port.type != PORT_8250_CIR) {
> if (uart->port.dev)
> uart_remove_one_port(&serial8250_reg, &uart->port);
> diff --git a/drivers/tty/serial/8250/8250_pnp.c b/drivers/tty/serial/8250/8250_pnp.c
> index 682a2fb..c880ed3 100644
> --- a/drivers/tty/serial/8250/8250_pnp.c
> +++ b/drivers/tty/serial/8250/8250_pnp.c
> @@ -15,6 +15,8 @@
> #include <linux/pci.h>
> #include <linux/pnp.h>
> #include <linux/string.h>
> +#include <acpi/acpi.h>
> +#include <acpi/acpi_bus.h>
> #include <linux/kernel.h>
> #include <linux/serial_core.h>
> #include <linux/bitops.h>
> @@ -427,6 +429,8 @@ static int
> serial_pnp_probe(struct pnp_dev *dev, const struct pnp_device_id *dev_id)
> {
> struct uart_8250_port uart;
> + struct acpi_device *acpi_dev;
> + char *serial_uid;
> int ret, line, flags = dev_id->driver_data;
> if (flags & UNKNOWN_DEV) {
> @@ -451,6 +455,14 @@ serial_pnp_probe(struct pnp_dev *dev, const struct pnp_device_id *dev_id)
> } else
> return -ENODEV;
> + if (dev->is_acpi) {
> + acpi_dev = dev->data;
> + serial_uid = acpi_dev->pnp.unique_id;
> + uart.is_acpi = 1;
> + if (kstrtoint(serial_uid, 10, &uart.uid))
> + return -EINVAL;
> + }
> +
> #ifdef SERIAL_DEBUG_PNP
> printk(KERN_DEBUG
> "Setup PNP port: port %x, mem 0x%lx, irq %d, type %d\n",
> diff --git a/include/linux/pnp.h b/include/linux/pnp.h
> index 195aafc..d745f14 100644
> --- a/include/linux/pnp.h
> +++ b/include/linux/pnp.h
> @@ -245,6 +245,7 @@ struct pnp_dev {
> u64 dma_mask;
> unsigned int number; /* used as an index, must be unique */
> int status;
> + unsigned char is_acpi; /* is acpi device */
> struct list_head global_list; /* node in global list of devices */
> struct list_head protocol_list; /* node in list of device's protocol */
> diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
> index af47a8a..8f1e1bd 100644
> --- a/include/linux/serial_8250.h
> +++ b/include/linux/serial_8250.h
> @@ -74,7 +74,9 @@ struct uart_8250_port {
> struct list_head list; /* ports on this IRQ */
> unsigned short capabilities; /* port capabilities */
> unsigned short bugs; /* port bugs */
> + int uid; /* ACPI device unique id */
> unsigned int tx_loadsz; /* transmit fifo load size */
> + unsigned char is_acpi; /* is acpi device */
> unsigned char acr;
> unsigned char ier;
> unsigned char lcr;
Regards,
Peter Hurley
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