From mboxrd@z Thu Jan 1 00:00:00 1970 From: peter@hurleysoftware.com (Peter Hurley) Date: Mon, 17 Aug 2015 12:04:16 -0400 Subject: earlycon issues in -next with amba-pl011 updates In-Reply-To: <20150811124043.GZ7557@n2100.arm.linux.org.uk> References: <20150810232312.GB10728@bivouac.eciton.net> <55C94247.8020701@hurleysoftware.com> <20150811124043.GZ7557@n2100.arm.linux.org.uk> Message-ID: <55D20600.6050204@hurleysoftware.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 08/11/2015 08:40 AM, Russell King - ARM Linux wrote: > On Mon, Aug 10, 2015 at 08:31:03PM -0400, Peter Hurley wrote: >> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c >> index 2af09ab..fd54991 100644 >> --- a/drivers/tty/serial/amba-pl011.c >> +++ b/drivers/tty/serial/amba-pl011.c >> @@ -2348,13 +2348,10 @@ static struct console amba_console = { >> >> static void pl011_putc(struct uart_port *port, int c) >> { >> - struct uart_amba_port *uap = >> - container_of(port, struct uart_amba_port, port); >> - >> - while (pl011_readw(uap, REG_FR) & UART01x_FR_TXFF) >> + while (readl(port->membase + UART01x_FR) & UART01x_FR_TXFF) >> ; >> - pl011_writeb(uap, c, REG_DR); >> - while (pl011_readw(uap, REG_FR) & uap->fr_busy) >> + writeb(c, port->membase + UART01x_DR); >> + while (readl(port->membase + UART01x_FR) & UART01x_FR_BUSY) >> ; > > These loops are wrong. Kernel coding style is that loops like this > will use cpu_relax() in them, just like the driver used to. This > was introduced by: > > commit 0d3c673e7881e691991b2a4745bd4f149603baa2 > Author: Rob Herring > Date: Fri Apr 18 17:19:57 2014 -0500 > > tty/serial: pl011: add generic earlycon support > > Also, the above readl()s should be readl_relaxed(), we don't need > barriered reads or to hit the L2 cache on those reads in the above code. This patch just reverts pl011 earlycon back to the existing mainline state. The amba-pl011 driver has many places where cpu_relax() is not used, so that seems like a good patch for -next during the 4.3-rc cycle. Similarly for read_relaxed() use in earlycon. Regards, Peter Hurley