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dc56ecb81a
linux/drivers/tty/serial/8250
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Josh Triplett dc56ecb81a serial: 8250: Support disabling mdelay-filled probes of 16550A variants 
The 8250 driver can probe for many variants of the venerable 16550A
serial port. Some of those probes involve long (20ms) mdelay calls,
which delay system boot. Modern systems and virtual machines don't have
those variants.

Provide a Kconfig option to disable probes for 16550A variants.
Disabling this speeds up the boot of a virtual machine with a serial
console by more than 20ms (a substantial fraction of the ~100ms needed
to boot a carefully configured VM).

Before:
[  +0.021919] 00:04: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
After:
[  +0.000097] 00:04: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Link: https://lore.kernel.org/r/20200111022513.GA166267@localhost
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-01-14 14:07:50 +01:00
..
8250_accent.c tty: serial: Remove redundant license text 2017-11-08 13:08:12 +01:00
8250_acorn.c tty: serial: Remove redundant license text 2017-11-08 13:08:12 +01:00
8250_aspeed_vuart.c tty/serial: Migrate aspeed_vuart to use has_sysrq 2019-12-17 15:16:17 +01:00
8250_bcm2835aux.c tty: Remove dev_err() usage after platform_get_irq() 2019-09-04 12:43:49 +02:00
8250_boca.c tty: serial: Remove redundant license text 2017-11-08 13:08:12 +01:00
8250_core.c tty/serial: Migrate 8250_fsl to use has_sysrq 2019-12-18 15:04:42 +01:00
8250_dma.c serial: 8250: factor out serial8250_{set,clear}_THRI() helpers 2019-06-18 09:36:55 +02:00
8250_dw.c serial: 8250_dw: Avoid double error messaging when IRQ absent 2019-11-04 17:45:31 +01:00
8250_dwlib.c serial: 8250_dw: split Synopsys DesignWare 8250 common functions 2019-09-04 12:43:52 +02:00
8250_dwlib.h serial: 8250_dw: split Synopsys DesignWare 8250 common functions 2019-09-04 12:43:52 +02:00
8250_early.c serial: 8250_early: Setup divider when uartclk is passed 2018-04-25 14:56:12 +02:00
8250_em.c headers: separate linux/mod_devicetable.h from linux/platform_device.h 2018-07-07 17:52:26 +02:00
8250_exar_st16c554.c tty: serial: Remove redundant license text 2017-11-08 13:08:12 +01:00
8250_exar.c serial: 8250_exar: Move Exar pieces to custom ->startup() 2019-10-15 21:02:04 +02:00
8250_fintek.c serial: 8250_fintek: Make fintek_8250_set_termios static 2019-03-28 00:29:03 +09:00
8250_fourport.c tty: serial: Remove redundant license text 2017-11-08 13:08:12 +01:00
8250_fsl.c tty/serial: Migrate 8250_fsl to use has_sysrq 2019-12-18 15:04:42 +01:00
8250_gsc.c tty: serial: Remove redundant license text 2017-11-08 13:08:12 +01:00
8250_hp300.c tty: add SPDX identifiers to all remaining files in drivers/tty/ 2017-11-08 13:08:12 +01:00
8250_hub6.c tty: serial: Remove redundant license text 2017-11-08 13:08:12 +01:00
8250_ingenic.c Serial: Ingenic: Add support for the X1000. 2019-01-30 09:31:30 +01:00
8250_lpc18xx.c tty: Remove dev_err() usage after platform_get_irq() 2019-09-04 12:43:49 +02:00
8250_lpss.c serial: 8250_lpss: Switch over to MSI interrupts 2019-10-04 14:58:05 +02:00
8250_men_mcb.c drivers: mcb: use symbol namespaces 2019-11-03 19:54:53 +01:00
8250_mid.c tty: serial: Remove redundant license text 2017-11-08 13:08:12 +01:00
8250_mtk.c serial: 8250-mtk: Use platform_get_irq_optional() for optional irq 2019-11-04 17:45:32 +01:00
8250_of.c tty/serial: Migrate 8250_fsl to use has_sysrq 2019-12-18 15:04:42 +01:00
8250_omap.c tty/serial: Migrate 8250_omap to use has_sysrq 2019-12-18 15:04:43 +01:00
8250_pci.c TTY/Serial patches for 5.5-rc1 2019-12-03 14:09:14 -08:00
8250_pnp.c serial: 8250_pnp: Move to struct dev_pm_ops 2019-09-04 12:43:46 +02:00
8250_port.c serial: 8250: Support disabling mdelay-filled probes of 16550A variants 2020-01-14 14:07:50 +01:00
8250_pxa.c serial: 8250_pxa: honor the port number from devicetree 2019-02-26 12:30:44 +01:00
8250_uniphier.c tty: Remove dev_err() usage after platform_get_irq() 2019-09-04 12:43:49 +02:00
8250.h tty/serial/8250: use mctrl_gpio helpers 2019-06-21 10:18:43 +02:00
Kconfig serial: 8250: Support disabling mdelay-filled probes of 16550A variants 2020-01-14 14:07:50 +01:00
Makefile serial: 8250_pci: Merge 8250_moxa to 8250_pci 2019-09-04 12:43:54 +02:00
serial_cs.c drivers/tty: add error handling for pcmcia_loop_config 2018-06-28 21:23:44 +09:00