86 lines
3.7 KiB
Diff
86 lines
3.7 KiB
Diff
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From: Matthias Schiffer <mschiffer@universe-factory.net>
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Date: Thu, 24 Mar 2016 18:30:26 +0100
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Subject: ar71xx: make bootconsole wait for both THRE and TEMT
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Original commit message:
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MIPS: ath79: make bootconsole wait for both THRE and TEMT
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This makes the ath79 bootconsole behave the same way as the generic 8250
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bootconsole.
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Also waiting for TEMT (transmit buffer is empty) instead of just THRE
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(transmit buffer is not full) ensures that all characters have been
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transmitted before the real serial driver starts reconfiguring the serial
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controller (which would sometimes result in garbage being transmitted.)
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This change does not cause a visible performance loss.
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In addition, this seems to fix a hang observed in certain configurations on
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many AR7xxx/AR9xxx SoCs during autoconfig of the real serial driver.
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A more complete follow-up patch will disable 8250 autoconfig for ath79
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altogether (the serial controller is detected as a 16550A, which is not
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fully compatible with the ath79 serial, and the autoconfig may lead to
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undefined behavior on ath79.)
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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
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new file mode 100644
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index 0000000..7be14ab
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--- /dev/null
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+++ b/target/linux/ar71xx/patches-3.18/103-MIPS-ath79-make-bootconsole-wait-for-both-THRE-and-T.patch
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@@ -0,0 +1,54 @@
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+From f1ba020af5076172c9d29006a747ccf40027fedc Mon Sep 17 00:00:00 2001
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+Message-Id: <f1ba020af5076172c9d29006a747ccf40027fedc.1458840219.git.mschiffer@universe-factory.net>
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+From: Matthias Schiffer <mschiffer@universe-factory.net>
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+Date: Thu, 24 Mar 2016 15:34:05 +0100
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+Subject: [PATCH] MIPS: ath79: make bootconsole wait for both THRE and TEMT
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+
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+This makes the ath79 bootconsole behave the same way as the generic 8250
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+bootconsole.
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+
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+Also waiting for TEMT (transmit buffer is empty) instead of just THRE
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+(transmit buffer is not full) ensures that all characters have been
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+transmitted before the real serial driver starts reconfiguring the serial
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+controller (which would sometimes result in garbage being transmitted.)
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+This change does not cause a visible performance loss.
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+
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+In addition, this seems to fix a hang observed in certain configurations on
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+many AR7xxx/AR9xxx SoCs during autoconfig of the real serial driver.
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+
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+A more complete follow-up patch will disable 8250 autoconfig for ath79
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+altogether (the serial controller is detected as a 16550A, which is not
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+fully compatible with the ath79 serial, and the autoconfig may lead to
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+undefined behavior on ath79.)
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+
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+Cc: <stable@vger.kernel.org>
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+Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
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+---
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+ arch/mips/ath79/early_printk.c | 6 ++++--
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+ 1 file changed, 4 insertions(+), 2 deletions(-)
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+
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+diff --git a/arch/mips/ath79/early_printk.c b/arch/mips/ath79/early_printk.c
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+index b955faf..d1adc59 100644
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+--- a/arch/mips/ath79/early_printk.c
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++++ b/arch/mips/ath79/early_printk.c
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+@@ -31,13 +31,15 @@ static inline void prom_putchar_wait(void __iomem *reg, u32 mask, u32 val)
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+ } while (1);
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+ }
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+
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++#define BOTH_EMPTY (UART_LSR_TEMT | UART_LSR_THRE)
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++
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+ static void prom_putchar_ar71xx(unsigned char ch)
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+ {
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+ void __iomem *base = (void __iomem *)(KSEG1ADDR(AR71XX_UART_BASE));
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+
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+- prom_putchar_wait(base + UART_LSR * 4, UART_LSR_THRE, UART_LSR_THRE);
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++ prom_putchar_wait(base + UART_LSR * 4, BOTH_EMPTY, BOTH_EMPTY);
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+ __raw_writel(ch, base + UART_TX * 4);
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+- prom_putchar_wait(base + UART_LSR * 4, UART_LSR_THRE, UART_LSR_THRE);
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++ prom_putchar_wait(base + UART_LSR * 4, BOTH_EMPTY, BOTH_EMPTY);
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+ }
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+
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+ static void prom_putchar_ar933x(unsigned char ch)
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+--
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+2.7.4
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+
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