[PATCH] ar71xx-make-bootconsole-wait-for-both-THRE-and-TEMT

[Tim Niemeyer]

Am Freitag, den 25.03.2016, 12:56 +0100 schrieb Christian Dresel:
> Fix the Race Condition on boot
Reviewed und applied.

Danke
Tim
> 
> 
> 
> Signed-off-by: Christian Dresel <fff at chrisi01.de>
> 
> 	new file:   build_patches/openwrt/0005-ar71xx-make-bootconsole-wait-for-both-THRE-and-TEMT.patch
> ---
>  ...e-bootconsole-wait-for-both-THRE-and-TEMT.patch | 86 ++++++++++++++++++++++
>  1 file changed, 86 insertions(+)
>  create mode 100644 build_patches/openwrt/0005-ar71xx-make-bootconsole-wait-for-both-THRE-and-TEMT.patch
> 
> diff --git a/build_patches/openwrt/0005-ar71xx-make-bootconsole-wait-for-both-THRE-and-TEMT.patch b/build_patches/openwrt/0005-ar71xx-make-bootconsole-wait-for-both-THRE-and-TEMT.patch
> new file mode 100644
> index 0000000..ada44bc
> --- /dev/null
> +++ b/build_patches/openwrt/0005-ar71xx-make-bootconsole-wait-for-both-THRE-and-TEMT.patch
> @@ -0,0 +1,86 @@
> +From: Matthias Schiffer <mschiffer at universe-factory.net>
> +Date: Thu, 24 Mar 2016 18:30:26 +0100
> +Subject: ar71xx: make bootconsole wait for both THRE and TEMT
> +
> +Original commit message:
> +
> +    MIPS: ath79: make bootconsole wait for both THRE and TEMT
> +
> +    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.)
> +
> +diff --git a/target/linux/ar71xx/patches-3.18/103-MIPS-ath79-make-bootconsole-wait-for-both-THRE-and-T.patch b/target/linux/ar71xx/patches-3.18/103-MIPS-ath79-make-bootconsole-wait-for-both-THRE-and-T.patch
> +new file mode 100644
> +index 0000000..7be14ab
> +--- /dev/null
> ++++ b/target/linux/ar71xx/patches-3.18/103-MIPS-ath79-make-bootconsole-wait-for-both-THRE-and-T.patch
> +@@ -0,0 +1,54 @@
> ++From f1ba020af5076172c9d29006a747ccf40027fedc Mon Sep 17 00:00:00 2001
> ++Message-Id: <f1ba020af5076172c9d29006a747ccf40027fedc.1458840219.git.mschiffer at universe-factory.net>
> ++From: Matthias Schiffer <mschiffer at universe-factory.net>
> ++Date: Thu, 24 Mar 2016 15:34:05 +0100
> ++Subject: [PATCH] MIPS: ath79: make bootconsole wait for both THRE and TEMT
> ++
> ++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.)
> ++
> ++Cc: <stable at vger.kernel.org>
> ++Signed-off-by: Matthias Schiffer <mschiffer at universe-factory.net>
> ++---
> ++ arch/mips/ath79/early_printk.c | 6 ++++--
> ++ 1 file changed, 4 insertions(+), 2 deletions(-)
> ++
> ++diff --git a/arch/mips/ath79/early_printk.c b/arch/mips/ath79/early_printk.c
> ++index b955faf..d1adc59 100644
> ++--- a/arch/mips/ath79/early_printk.c
> +++++ b/arch/mips/ath79/early_printk.c
> ++@@ -31,13 +31,15 @@ static inline void prom_putchar_wait(void __iomem *reg, u32 mask, u32 val)
> ++ 	} 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)
> ++-- 
> ++2.7.4
> ++
> +
> -- 
> 2.1.4
> 

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