Public bug reported: The upstream commit summarizes the problem well, so I'll just paste it here:
commit d8a4995bcea168dfac8ee41c28c79109907e4fba Author: Christopher Covington <[email protected]> Date: Wed Feb 15 16:39:43 2017 -0500 tty: pl011: Work around QDF2400 E44 stuck BUSY bit The Qualcomm Datacenter Technologies QDF2400 family of SoCs contains a custom (non-PrimeCell) implementation of the SBSA UART. Occasionally the BUSY bit in the Flag Register gets stuck as 1, erratum 44 for both 2432v1 and 2400v1 SoCs.Checking that the Transmit FIFO Empty (TXFE) bit is 0, instead of checking that the BUSY bit is 1, works around the issue. To facilitate this substitution of flags and values, introduce vendor-specific inversion of Feature Register bits when UART AMBA Port (UAP) data is available. For the earlycon case, prior to UAP availability, implement alternative putc and early_write functions. Similar to what how ARMv8 ACPI PCI quirks are detected during MCFG parsing, check the OEM fields of the Serial Port Console Redirection (SPCR) ACPI table to determine if the current platform is known to be affected by the erratum. Signed-off-by: Christopher Covington <[email protected]> Acked-by: Russell King <[email protected]> Acked-by: Timur Tabi <[email protected]> Acked-by: Mark Rutland <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> ** Affects: linux (Ubuntu) Importance: High Assignee: dann frazier (dannf) Status: In Progress -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1671600 Title: tty: pl011: Work around QDF2400 E44 stuck BUSY bit To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1671600/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
