From f1ba020af5076172c9d29006a747ccf40027fedc Mon Sep 17 00:00:00 2001 Message-Id: From: Matthias Schiffer 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: Signed-off-by: Matthias Schiffer --- 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)