linux-kernel - Re: [PATCHv2 1/2] amba pl011: workaround for uart registers lockup

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Message-ID: <20110517182356.GA17703@kroah.com>
Date:	Tue, 17 May 2011 11:23:56 -0700
From:	Greg KH <greg@...ah.com>
To:	Shreshtha Kumar SAHU <shreshthakumar.sahu@...ricsson.com>
Cc:	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
	rmk+kernel@....linux.org.uk, linus.walleij@...ricsson.com,
	alan@...ux.intel.com
Subject: Re: [PATCHv2 1/2] amba pl011: workaround for uart registers lockup

On Tue, May 17, 2011 at 10:50:17AM +0530, Shreshtha Kumar SAHU wrote:
> From: Shreshtha Kumar Sahu <shreshthakumar.sahu@...ricsson.com>
> 
> This workaround aims to break the deadlock situation
> which raises during continuous transfer of data for long
> duration over uart with hardware flow control. It is
> observed that CTS interrupt cannot be cleared in uart
> interrupt register (ICR). Hence further transfer over
> uart gets blocked.
> 
> It is seen that during such deadlock condition ICR
> don't get cleared even on multiple write. This leads
> pass_counter to decrease and finally reach zero. This
> can be taken as trigger point to run this UART_BT_WA.
> 
> Workaround backups the register configuration, does soft
> reset of UART using BIT-0 of PRCC_K_SOFTRST_SET/CLEAR
> registers and restores the registers.
> 
> This patch also provides support for uart init and exit
> function calls if present.

Why?  You don't use these callbacks in this driver, so why add them?

confused,

greg k-h
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