From mboxrd@z Thu Jan  1 00:00:00 1970
From: rmallon@gmail.com (Ryan Mallon)
Date: Wed, 12 Dec 2012 11:25:02 +1100
Subject: [PATCH] ARM: ep93xx: properly wait for UART FIFO to be empty
In-Reply-To: <1836468.ZU3cPkV103@bender>
References: <1836468.ZU3cPkV103@bender>
Message-ID: <50C7CEDE.4030703@gmail.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

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@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);
>  }
>