From 969f0f69e8d0c4b2706c9c31589c2ac39806dafd Mon Sep 17 00:00:00 2001 From: Matthias Schiffer Date: Thu, 24 Mar 2016 16:02:52 +0100 Subject: MIPS: ath79: make bootconsole wait for both THRE and TEMT 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 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman --- arch/mips/ath79/early_printk.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'arch/mips/ath79/early_printk.c') diff --git a/arch/mips/ath79/early_printk.c b/arch/mips/ath79/early_printk.c index b955fafc58ba..d1adc59af5bf 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) -- cgit v1.2.3