From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Mark A. Greer" Subject: Re: [PATCH 3/3] ARM: OMAP: AM35xx: fix UART4 softreset Date: Thu, 10 May 2012 12:37:29 -0700 Message-ID: <20120510193729.GE20494@animalcreek.com> References: <20120510172449.13418.66815.stgit@dusk> <20120510172918.13418.64781.stgit@dusk> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail20.dotsterhost.com ([66.11.232.73]:36717 "EHLO mail20.dotsterhost.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760771Ab2EJTha (ORCPT ); Thu, 10 May 2012 15:37:30 -0400 Content-Disposition: inline In-Reply-To: <20120510172918.13418.64781.stgit@dusk> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Paul Walmsley Cc: linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Kyle Manna , Ranjith Lohithakshan , =?iso-8859-1?Q?Beno=EEt?= Cousson On Thu, May 10, 2012 at 11:29:19AM -0600, Paul Walmsley wrote: > During kernel init, the AM3505/AM3517 UART4 cannot complete its softr= eset: >=20 > omap_hwmod: uart4: softreset failed (waited 10000 usec) >=20 > This also results in another warning later in the boot process: >=20 > omap_hwmod: uart4: enabled state can only be entered from initialized= , idle, or disabled state >=20 > >From empirical observation, the AM35xx UART4 IP block requires eithe= r > uart1_fck or uart2_fck to be enabled while UART4 resets. Otherwise > the reset will never complete. So this patch adds uart1_fck as an > optional clock for UART4 and adds the appropriate hwmod flag to cause > uart1_fck to be enabled during the reset process. (The choice of > uart1_fck over uart2_fck was arbitrary.) >=20 > Unfortunately this observation raises many questions. Is it necessar= y > for uart1_fck or uart2_fck to be controlled with uart4_fck for the > UART4 to work correctly? What exactly do the AM35xx UART4 clock > tree and the related PRCM idle management FSMs look like? If anyone > has the ability to answer these questions through empirical functiona= l > testing, or hardware information from the AM35xx designers, it would > be greatly appreciated. >=20 > Cc: Beno=EEt Cousson > Cc: Kyle Manna > Cc: Mark A. Greer > Cc: Ranjith Lohithakshan > Signed-off-by: Paul Walmsley Acked-by: Mark A. Greer (on an am3517evm) Mark -- To unsubscribe from this list: send the line "unsubscribe linux-omap" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html