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[PATCH 3.14 03/23] MIPS: ath79: make bootconsole wait for both THRE and TEMT

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3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Matthias Schiffer <mschiffer@universe-factory.net>

commit f5b556c94c8490d42fea79d7b4ae0ecbc291e69d upstream.

This makes the ath79 bootconsole behave the same way as the generic 8250
bootconsole.

Also waiting for TEMT (transmit buffer is empty) instead of just THRE
(transmit buffer is not full) ensures that all characters have been
transmitted before the real serial driver starts reconfiguring the serial
controller (which would sometimes result in garbage being transmitted.)
This change does not cause a visible performance loss.

In addition, this seems to fix a hang observed in certain configurations on
many AR7xxx/AR9xxx SoCs during autoconfig of the real serial driver.

A more complete follow-up patch will disable 8250 autoconfig for ath79
altogether (the serial controller is detected as a 16550A, which is not
fully compatible with the ath79 serial, and the autoconfig may lead to
undefined behavior on ath79.)

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/ath79/early_printk.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/arch/mips/ath79/early_printk.c
+++ b/arch/mips/ath79/early_printk.c
@@ -31,13 +31,15 @@ static inline void prom_putchar_wait(voi
 	} while (1);
 }
 
+#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
+
 static void prom_putchar_ar71xx(unsigned char ch)
 {
 	void __iomem *base = (void __iomem *)(KSEG1ADDR(AR71XX_UART_BASE));
 
-	prom_putchar_wait(base + UART_LSR * 4, UART_LSR_THRE, UART_LSR_THRE);
+	prom_putchar_wait(base + UART_LSR * 4, BOTH_EMPTY, BOTH_EMPTY);
 	__raw_writel(ch, base + UART_TX * 4);
-	prom_putchar_wait(base + UART_LSR * 4, UART_LSR_THRE, UART_LSR_THRE);
+	prom_putchar_wait(base + UART_LSR * 4, BOTH_EMPTY, BOTH_EMPTY);
 }
 
 static void prom_putchar_ar933x(unsigned char ch)

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[PATCH 3.14 00/23] 3.14.72-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-05 23:50 +0200
  [PATCH 3.14 07/23] aacraid: Fix for aac_command_thread hang Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-05 23:50 +0200
  [PATCH 3.14 11/23] pipe: Fix buffer offset after partially failed read Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-05 23:50 +0200
    Re: [PATCH 3.14 11/23] pipe: Fix buffer offset after partially failed  read Jiri Slaby <jslaby@suse.cz> - 2016-06-07 16:00 +0200
      Re: [PATCH 3.14 11/23] pipe: Fix buffer offset after partially  failed read Ben Hutchings <ben@decadent.org.uk> - 2016-06-07 16:50 +0200
  [PATCH 3.14 08/23] cpuidle: Indicate when a device has been unregistered Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-05 23:50 +0200
  [PATCH 3.14 03/23] MIPS: ath79: make bootconsole wait for both THRE and TEMT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 05/23] ath5k: Change led pin configuration for compaq c700 laptop Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 19/23] ext4: silence UBSAN in ext4_mb_init() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 04/23] Input: uinput - handle compat ioctl for UI_SET_PHYS Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 13/23] xen/events: Dont move disabled irqs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 10/23] rtlwifi: Fix logic error in enter/exit power-save mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 01/23] MIPS: math-emu: Fix jalr emulation when rd == $0 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 06/23] aacraid: Relinquish CPU during timeout wait Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 17/23] ext4: fix hang when processing corrupted orphaned inode list Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 02/23] MIPS: Fix siginfo.h to use strict posix types Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 18/23] ext4: address UBSAN warning in mb_find_order_for_block() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  [PATCH 3.14 15/23] drm/gma500: Fix possible out of bounds read Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-06 01:10 +0200
  Re: [PATCH 3.14 00/23] 3.14.72-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2016-06-06 19:30 +0200
    Re: [PATCH 3.14 00/23] 3.14.72-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-06-08 02:30 +0200
  Re: [PATCH 3.14 00/23] 3.14.72-stable review Guenter Roeck <linux@roeck-us.net> - 2016-06-07 05:50 +0200

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