earlycon issues in -next with amba-pl011 updates
From: Leif Lindholm <hidden>
Date: 2015-08-11 10:07:21
Also in:
linux-serial
Hi Peter, On Mon, Aug 10, 2015 at 08:31:03PM -0400, Peter Hurley wrote:
quoted
The issue only appears with earlycon on command line, for pl011 consoles. Some investigation shows that the cause lies with commit 7b753f318d14 ("uart: pl011: Introduce register accessor") and commit 2c096a9eedc6 ("uart: pl011: Introduce register look up table") Specifically, the changes to pl011_putc() are incorrect: The new pl011_ accessors take a (struct uart_amba_port *) input, but pl011_putc() directly uses the incoming (struct uart_port *) for this. Apart from ending up with an unintended/incorrect UART base address, the introduction of the lookup table for register offsets also means the accessors try to dereference (struct uart_amba_port *)->reg_lut.Thanks for the bug report and bisect, and apologies for the breakage; I should have caught that on review.
I wouldn't have found it if I didn't have the boot failure to track down, and I'm _not_ going to tell you how long I spent doing that.
Would you please test the patch below and see if that resolves the problem for you?
Yeah, that's a more straightforward fix.
quoted hunk ↗ jump to hunk
PS - _NOT_ even compile-tested, sorry.--- >% ---Subject: [PATCH] serial: pl011: Fix earlycon register LUT breakage Commit 7b753f318d14 ("uart: pl011: Introduce register accessor") mistakenly used the register LUT i/o accessors for the pl011 earlycon. Since the port has not been probed at earlycon time, the struct uart_amba_port (and register LUTs) are uninitialized. Use direct register addressing for pl011 earlycon; other h/w supported by the amba-pl011 driver should declare an alternate earlycon. Cc: Jun Nie <redacted> Signed-off-by: Peter Hurley <redacted> --- drivers/tty/serial/amba-pl011.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)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) ; }-- 2.5.0
It works, but builds with:
drivers/tty/serial/amba-pl011.c:329:13: warning: ?pl011_writeb?
defined but not used [-Wunused-function]
static void pl011_writeb(struct uart_amba_port *uap, u8 val, int
index)
^
I was dithering about whether having _relaxed accessors in post boot
code and plain ones in earlycon was an issue, but I guess it doesn't
matter much.
/
Leif