serial: sh-sci: Reorder the SCxTDR write after the TDxE clear.

Under qemu there is a race between the TDxE read-and-clear and the SCxTDR
write. While on hardware it can be gauranteed that the read-and-clear
will happen prior to the character being written out, no such assumption
can be made under emulation. As this path happens with IRQs off and the
hardware itself doesn't care about the ordering, move the SCxTDR write
until after the read-and-clear.

Signed-off-by: Vladimir Prus <vladimir@codesourcery.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

diff --git a/arch/sh/kernel/early_printk.c b/arch/sh/kernel/early_printk.c
index 98a29a78230179f54425d27ea35947beb4de405e..a952dcf9999d43bedbef8ff275aa3517fb13ab91 100644 (file)
--- a/arch/sh/kernel/early_printk.c
+++ b/arch/sh/kernel/early_printk.c
@@ -85,9 +85,9 @@ static void scif_sercon_putc(int c)
        while (((sci_in(&scif_port, SCFDR) & EPK_FIFO_BITS) >= EPK_FIFO_SIZE))
                ;
 
-       sci_out(&scif_port, SCxTDR, c);
        sci_in(&scif_port, SCxSR);
        sci_out(&scif_port, SCxSR, 0xf3 & ~(0x20 | 0x40));
+       sci_out(&scif_port, SCxTDR, c);
 
        while ((sci_in(&scif_port, SCxSR) & 0x40) == 0)
                ;

diff --git a/drivers/serial/sh-sci.c b/drivers/serial/sh-sci.c
index 518c0321e4d35b98f01e75bfaaf6e99a784ad473..165fc010978c2624a7a45730f403b505ed48e726 100644 (file)
--- a/drivers/serial/sh-sci.c
+++ b/drivers/serial/sh-sci.c
@@ -144,9 +144,9 @@ static void put_char(struct uart_port *port, char c)
                status = sci_in(port, SCxSR);
        } while (!(status & SCxSR_TDxE(port)));
 
-       sci_out(port, SCxTDR, c);
        sci_in(port, SCxSR);            /* Dummy read */
        sci_out(port, SCxSR, SCxSR_TDxE_CLEAR(port));
+       sci_out(port, SCxTDR, c);
 
        spin_unlock_irqrestore(&port->lock, flags);
 }