diff options
Diffstat (limited to 'Documentation/arch/ia64/serial.rst')
| -rw-r--r-- | Documentation/arch/ia64/serial.rst | 165 |
1 files changed, 0 insertions, 165 deletions
diff --git a/Documentation/arch/ia64/serial.rst b/Documentation/arch/ia64/serial.rst deleted file mode 100644 index 1de70c305a..0000000000 --- a/Documentation/arch/ia64/serial.rst +++ /dev/null @@ -1,165 +0,0 @@ -============== -Serial Devices -============== - -Serial Device Naming -==================== - - As of 2.6.10, serial devices on ia64 are named based on the - order of ACPI and PCI enumeration. The first device in the - ACPI namespace (if any) becomes /dev/ttyS0, the second becomes - /dev/ttyS1, etc., and PCI devices are named sequentially - starting after the ACPI devices. - - Prior to 2.6.10, there were confusing exceptions to this: - - - Firmware on some machines (mostly from HP) provides an HCDP - table[1] that tells the kernel about devices that can be used - as a serial console. If the user specified "console=ttyS0" - or the EFI ConOut path contained only UART devices, the - kernel registered the device described by the HCDP as - /dev/ttyS0. - - - If there was no HCDP, we assumed there were UARTs at the - legacy COM port addresses (I/O ports 0x3f8 and 0x2f8), so - the kernel registered those as /dev/ttyS0 and /dev/ttyS1. - - Any additional ACPI or PCI devices were registered sequentially - after /dev/ttyS0 as they were discovered. - - With an HCDP, device names changed depending on EFI configuration - and "console=" arguments. Without an HCDP, device names didn't - change, but we registered devices that might not really exist. - - For example, an HP rx1600 with a single built-in serial port - (described in the ACPI namespace) plus an MP[2] (a PCI device) has - these ports: - - ========== ========== ============ ============ ======= - Type MMIO pre-2.6.10 pre-2.6.10 2.6.10+ - address - (EFI console (EFI console - on builtin) on MP port) - ========== ========== ============ ============ ======= - builtin 0xff5e0000 ttyS0 ttyS1 ttyS0 - MP UPS 0xf8031000 ttyS1 ttyS2 ttyS1 - MP Console 0xf8030000 ttyS2 ttyS0 ttyS2 - MP 2 0xf8030010 ttyS3 ttyS3 ttyS3 - MP 3 0xf8030038 ttyS4 ttyS4 ttyS4 - ========== ========== ============ ============ ======= - -Console Selection -================= - - EFI knows what your console devices are, but it doesn't tell the - kernel quite enough to actually locate them. The DIG64 HCDP - table[1] does tell the kernel where potential serial console - devices are, but not all firmware supplies it. Also, EFI supports - multiple simultaneous consoles and doesn't tell the kernel which - should be the "primary" one. - - So how do you tell Linux which console device to use? - - - If your firmware supplies the HCDP, it is simplest to - configure EFI with a single device (either a UART or a VGA - card) as the console. Then you don't need to tell Linux - anything; the kernel will automatically use the EFI console. - - (This works only in 2.6.6 or later; prior to that you had - to specify "console=ttyS0" to get a serial console.) - - - Without an HCDP, Linux defaults to a VGA console unless you - specify a "console=" argument. - - NOTE: Don't assume that a serial console device will be /dev/ttyS0. - It might be ttyS1, ttyS2, etc. Make sure you have the appropriate - entries in /etc/inittab (for getty) and /etc/securetty (to allow - root login). - -Early Serial Console -==================== - - The kernel can't start using a serial console until it knows where - the device lives. Normally this happens when the driver enumerates - all the serial devices, which can happen a minute or more after the - kernel starts booting. - - 2.6.10 and later kernels have an "early uart" driver that works - very early in the boot process. The kernel will automatically use - this if the user supplies an argument like "console=uart,io,0x3f8", - or if the EFI console path contains only a UART device and the - firmware supplies an HCDP. - -Troubleshooting Serial Console Problems -======================================= - - No kernel output after elilo prints "Uncompressing Linux... done": - - - You specified "console=ttyS0" but Linux changed the device - to which ttyS0 refers. Configure exactly one EFI console - device[3] and remove the "console=" option. - - - The EFI console path contains both a VGA device and a UART. - EFI and elilo use both, but Linux defaults to VGA. Remove - the VGA device from the EFI console path[3]. - - - Multiple UARTs selected as EFI console devices. EFI and - elilo use all selected devices, but Linux uses only one. - Make sure only one UART is selected in the EFI console - path[3]. - - - You're connected to an HP MP port[2] but have a non-MP UART - selected as EFI console device. EFI uses the MP as a - console device even when it isn't explicitly selected. - Either move the console cable to the non-MP UART, or change - the EFI console path[3] to the MP UART. - - Long pause (60+ seconds) between "Uncompressing Linux... done" and - start of kernel output: - - - No early console because you used "console=ttyS<n>". Remove - the "console=" option if your firmware supplies an HCDP. - - - If you don't have an HCDP, the kernel doesn't know where - your console lives until the driver discovers serial - devices. Use "console=uart,io,0x3f8" (or appropriate - address for your machine). - - Kernel and init script output works fine, but no "login:" prompt: - - - Add getty entry to /etc/inittab for console tty. Look for - the "Adding console on ttyS<n>" message that tells you which - device is the console. - - "login:" prompt, but can't login as root: - - - Add entry to /etc/securetty for console tty. - - No ACPI serial devices found in 2.6.17 or later: - - - Turn on CONFIG_PNP and CONFIG_PNPACPI. Prior to 2.6.17, ACPI - serial devices were discovered by 8250_acpi. In 2.6.17, - 8250_acpi was replaced by the combination of 8250_pnp and - CONFIG_PNPACPI. - - - -[1] - http://www.dig64.org/specifications/agreement - The table was originally defined as the "HCDP" for "Headless - Console/Debug Port." The current version is the "PCDP" for - "Primary Console and Debug Port Devices." - -[2] - The HP MP (management processor) is a PCI device that provides - several UARTs. One of the UARTs is often used as a console; the - EFI Boot Manager identifies it as "Acpi(HWP0002,700)/Pci(...)/Uart". - The external connection is usually a 25-pin connector, and a - special dongle converts that to three 9-pin connectors, one of - which is labelled "Console." - -[3] - EFI console devices are configured using the EFI Boot Manager - "Boot option maintenance" menu. You may have to interrupt the - boot sequence to use this menu, and you will have to reset the - box after changing console configuration. |