From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <scottwood@freescale.com>
Received: from az33egw01.freescale.net (az33egw01.freescale.net
	[192.88.158.102])
	(using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits))
	(Client CN "az33egw01.freescale.net",
	Issuer "Thawte Premium Server CA" (verified OK))
	by ozlabs.org (Postfix) with ESMTPS id 355B1DDEEB
	for <linuxppc-dev@ozlabs.org>; Sat, 29 Mar 2008 05:53:52 +1100 (EST)
Message-ID: <47ED3EC5.8030508@freescale.com>
Date: Fri, 28 Mar 2008 13:53:57 -0500
From: Scott Wood <scottwood@freescale.com>
MIME-Version: 1.0
To: Anton Vorontsov <avorontsov@ru.mvista.com>
Subject: Re: [PATCH] mtd/nand/fsl_elbc_nand: workaround for hangs on MPC837X
References: <20080328184303.GA25882@localhost.localdomain>
In-Reply-To: <20080328184303.GA25882@localhost.localdomain>
Content-Type: text/plain; charset=UTF-8; format=flowed
Cc: linuxppc-dev@ozlabs.org, linux-mtd@lists.infradead.org
List-Id: Linux on PowerPC Developers Mail List <linuxppc-dev.ozlabs.org>
List-Unsubscribe: <https://ozlabs.org/mailman/listinfo/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=unsubscribe>
List-Archive: <http://ozlabs.org/pipermail/linuxppc-dev>
List-Post: <mailto:linuxppc-dev@ozlabs.org>
List-Help: <mailto:linuxppc-dev-request@ozlabs.org?subject=help>
List-Subscribe: <https://ozlabs.org/mailman/listinfo/linuxppc-dev>,
	<mailto:linuxppc-dev-request@ozlabs.org?subject=subscribe>

Anton Vorontsov wrote:
> @@ -495,6 +495,16 @@ static void fsl_elbc_write_buf(struct mtd_info *mtd, const u8 *buf, int len)
>  	}
>  
>  	memcpy_toio(&ctrl->addr[ctrl->index], buf, len);
> +#ifdef CONFIG_PPC_MPC837x
> +	/*
> +	 * This is workaround for the weird elbc hangs on the MPC837X CPUs,
> +	 * Scott Wood says: "...perhaps difference in how long it takes a
> +	 * write to make it through the localbus compared to a write to IMMR
> +	 * is causing problems, and sync isn't helping for some reason."
> +	 * Reading back the last byte helps though.
> +	 */
> +	in_8(&ctrl->addr[ctrl->index] + len - 1);
> +#endif

Let's do it regardless of chip -- odds are the issue exists on all 
implementations, and it's just a function of what frequencies things are 
running at.

-Scott