[PATCH] ARM: ep93xx: properly wait for UART FIFO to be empty
Ryan Mallon
rmallon at gmail.com
Tue Dec 11 19:25:02 EST 2012
On 11/12/12 08:21, Florian Fainelli wrote:
> This patch changes the busy-waiting loop around in the decompressor
> putc() function on the UART FIFO register. Without a proper wait, the
> output of the decompressor was corrupted like this:
>
> Uncompressing Linx. done, booting th enl
>
> To highlight the issue more evidently, looping 100 times instead of 1000
> makes the issue appear much faster. This patch takes the approach of
> using an active while loop until the FIFO is empty (not FULL).
> This issue happened to me on Sim.One running at 200Mhz.
>
> Signed-off-by: Florian Fainelli <florian at openwrt.org>
> ---
> Ryan, this is based on your ep93xx-fixes branch, thanks!
Thank you,
Applied to ep93xx-fixes.
~Ryan
>
> arch/arm/mach-ep93xx/include/mach/uncompress.h | 10 +++-------
> 1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm/mach-ep93xx/include/mach/uncompress.h b/arch/arm/mach-ep93xx/include/mach/uncompress.h
> index 16026c2..d64274f 100644
> --- a/arch/arm/mach-ep93xx/include/mach/uncompress.h
> +++ b/arch/arm/mach-ep93xx/include/mach/uncompress.h
> @@ -47,13 +47,9 @@ static void __raw_writel(unsigned int value, unsigned int ptr)
>
> static inline void putc(int c)
> {
> - int i;
> -
> - for (i = 0; i < 1000; i++) {
> - /* Transmit fifo not full? */
> - if (!(__raw_readb(PHYS_UART_FLAG) & UART_FLAG_TXFF))
> - break;
> - }
> + /* Transmit fifo not full? */
> + while (__raw_readb(PHYS_UART_FLAG) & UART_FLAG_TXFF)
> + ;
>
> __raw_writeb(c, PHYS_UART_DATA);
> }
>
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