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tty: pl011: fix initialization order of QDF2400 E44

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The work-around for Qualcomm Technologies QDF2400 Erratum 44 hinges on a
global variable defined in the pl011 driver.  The ACPI SPCR parsing code
determines whether the work-around is needed, and if so, it changes the
console name from "pl011" to "qdf2400_e44".  The expectation is that
the pl011 driver will implement the work-around when it sees the console
name.  The global variable qdf2400_e44_present is set when that happens.

The problem is that work-around needs to be enabled when the pl011
driver probes, not when the console name is queried.  However, sbsa_probe()
is called before pl011_console_match().  The work-around appeared to work
previously because the default console on QDF2400 platforms was always
ttyAMA1.  The first time sbsa_probe() is called (for ttyAMA0),
qdf2400_e44_present is still false.  Then pl011_console_match() is called,
and it sets qdf2400_e44_present to true.  All subsequent calls to
sbsa_probe() enable the work-around.

The solution is to move the global variable into spcr.c and let the
pl011 driver query it during probe time.  This works because all QDF2400
platforms require SPCR, so parse_spcr() will always be called.
pl011_console_match still checks for the "qdf2400_e44" console name,
but it doesn't do anything else special.

Fixes: 5a0722b898 ("tty: pl011: use "qdf2400_e44" as the earlycon name for QDF2400 E44")
Tested-by: Jeffrey Hugo <[email protected]>
Signed-off-by: Timur Tabi <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Timur Tabi 2017-07-27 16:15:52 -05:00 • committed by Greg Kroah-Hartman
commit 37ef38f3f8
3 changed files with 54 additions and 20 deletions
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36
drivers/acpi/spcr.c
View file

@ -16,6 +16,16 @@
#include <linux/kernel.h>
#include <linux/serial_core.h>
/*
* Erratum 44 for QDF2432v1 and QDF2400v1 SoCs describes the BUSY bit as
* occasionally getting stuck as 1. To avoid the potential for a hang, check
* TXFE == 0 instead of BUSY == 1. This may not be suitable for all UART
* implementations, so only do so if an affected platform is detected in
* parse_spcr().
*/
bool qdf2400_e44_present;
EXPORT_SYMBOL(qdf2400_e44_present);
/*
* Some Qualcomm Datacenter Technologies SoCs have a defective UART BUSY bit.
* Detect them by examining the OEM fields in the SPCR header, similiar to PCI
@ -147,8 +157,30 @@ int __init parse_spcr(bool earlycon)
goto done;
}
if (qdf2400_erratum_44_present(&table->header))
uart = "qdf2400_e44";
/*
* If the E44 erratum is required, then we need to tell the pl011
* driver to implement the work-around.
*
* The global variable is used by the probe function when it
* creates the UARTs, whether or not they're used as a console.
*
* If the user specifies "traditional" earlycon, the qdf2400_e44
* console name matches the EARLYCON_DECLARE() statement, and
* SPCR is not used. Parameter "earlycon" is false.
*
* If the user specifies "SPCR" earlycon, then we need to update
* the console name so that it also says "qdf2400_e44". Parameter
* "earlycon" is true.
*
* For consistency, if we change the console name, then we do it
* for everyone, not just earlycon.
*/
if (qdf2400_erratum_44_present(&table->header)) {
qdf2400_e44_present = true;
if (earlycon)
uart = "qdf2400_e44";
}
if (xgene_8250_erratum_present(table))
iotype = "mmio32";