From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751624AbbAVH2z (ORCPT ); Thu, 22 Jan 2015 02:28:55 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:39913 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750946AbbAVH2s (ORCPT ); Thu, 22 Jan 2015 02:28:48 -0500 Date: Thu, 22 Jan 2015 08:28:39 +0100 From: Sascha Hauer To: Robin Gong Cc: dan.j.williams@intel.com, vinod.koul@intel.com, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] dma: imx-sdma: switch to dynamic context mode after script loaded Message-ID: <20150122072839.GO12209@pengutronix.de> References: <1421899177-30406-1-git-send-email-b38343@freescale.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1421899177-30406-1-git-send-email-b38343@freescale.com> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 08:23:20 up 98 days, 18:37, 123 users, load average: 0.01, 0.03, 0.05 User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: sha@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 22, 2015 at 11:59:37AM +0800, Robin Gong wrote: > Below comments got from Page4724 of Reference Manual of i.mx6q: > http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6DQRM.pdf > > --"Static context mode should be used for the first channel called > after reset to ensure that the all context RAM for that channel is > initialized during the context SAVE phase when the channel is > done or yields. Subsequent calls to the same channel or > different channels may use any of the dynamic context modes. > This will ensure that all context locations for the bootload > channel are initialized, and prevent undefined values in context > RAM from being loaded during the context restore if the > channel is re-started later" > > Unfortunately, the rule was broken by commit(5b28aa319bba96987316425a1131813d87cbab35) > .This patch just take them back. > > Signed-off-by: Robin Gong > --- > drivers/dma/imx-sdma.c | 11 ++++++++--- > 1 file changed, 8 insertions(+), 3 deletions(-) > > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c > index d0df198..d84b7a8 100644 > --- a/drivers/dma/imx-sdma.c > +++ b/drivers/dma/imx-sdma.c > @@ -330,6 +330,8 @@ struct sdma_engine { > const struct sdma_driver_data *drvdata; > }; > > +static bool channel0_first; Nah, don't break the multi instance capability of drivers without a reason. Don't use global static variables in driver context. > + > static struct sdma_driver_data sdma_imx31 = { > .chnenbl0 = SDMA_CHNENBL0_IMX31, > .num_events = 32, > @@ -531,6 +533,12 @@ static int sdma_run_channel0(struct sdma_engine *sdma) > dev_err(sdma->dev, "Timeout waiting for CH0 ready\n"); > } > > + if (!channel0_first) { > + /* Set bits of CONFIG register with given context switching mode */ > + writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + SDMA_H_CONFIG); > + channel0_first = true; > + } You don't need a variable. How about: if (readl(sdma->regs + SDMA_H_CONFIG) == 0) writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + SDMA_H_CONFIG); Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |