Public bug reported:
The upstream commit summarizes the problem well, so I'll just paste it
here:
commit d8a4995bcea168dfac8ee41c28c79109907e4fba
Author: Christopher Covington <c...@codeaurora.org>
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 <c...@codeaurora.org>
Acked-by: Russell King <rmk+ker...@armlinux.org.uk>
Acked-by: Timur Tabi <ti...@codeaurora.org>
Acked-by: Mark Rutland <mark.rutl...@arm.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
** Affects: linux (Ubuntu)
Importance: High
Assignee: dann frazier (dannf)
Status: In Progress
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https://bugs.launchpad.net/bugs/1671600
Title:
tty: pl011: Work around QDF2400 E44 stuck BUSY bit
Status in linux package in Ubuntu:
In Progress
Bug description:
The upstream commit summarizes the problem well, so I'll just paste it
here:
commit d8a4995bcea168dfac8ee41c28c79109907e4fba
Author: Christopher Covington <c...@codeaurora.org>
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 <c...@codeaurora.org>
Acked-by: Russell King <rmk+ker...@armlinux.org.uk>
Acked-by: Timur Tabi <ti...@codeaurora.org>
Acked-by: Mark Rutland <mark.rutl...@arm.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
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