From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938793AbcHJSx6 (ORCPT ); Wed, 10 Aug 2016 14:53:58 -0400 Received: from mga14.intel.com ([192.55.52.115]:37156 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S938743AbcHJSxz (ORCPT ); Wed, 10 Aug 2016 14:53:55 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,501,1464678000"; d="scan'208";a="1023176792" Date: Wed, 10 Aug 2016 22:58:05 +0530 From: Vinod Koul To: Sinan Kaya Cc: Russell King - ARM Linux , linux-arm-msm@vger.kernel.org, timur@codeaurora.org, linux-kernel@vger.kernel.org, Christopher Covington , dmaengine@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] dmaengine: qcom_hidma: release the descriptor before the callback Message-ID: <20160810172805.GH9681@localhost> References: <1468465076-27324-1-git-send-email-okaya@codeaurora.org> <20160724062425.GW9681@localhost> <971733d9-fd18-2a1b-07c0-349b47747d49@codeaurora.org> <20160804125525.GF9681@localhost> <71a15611-645f-7523-1c26-14b420aff667@codeaurora.org> <20160804144003.GV1041@n2100.armlinux.org.uk> <20160808090203.GY9681@localhost> <21475c6e-a5f8-5125-3998-f3995ce67c4d@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <21475c6e-a5f8-5125-3998-f3995ce67c4d@codeaurora.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 08, 2016 at 10:45:24AM -0400, Sinan Kaya wrote: > On 8/8/2016 5:02 AM, Vinod Koul wrote: > >> What Vinod is telling me that I need to set the cookie to complete > >> > whether the transaction is successful or not if the request was accepted > >> > by HW. xyz_tx_status is just an indication that the transaction was accepted > >> > by HW. An error can happen as a result of transaction execution. > > Nope, if the txn is completed you mark it complete. If you can detect error > > (can you??) then you can report DMA_ERROR. > > > > Yes, the HW reports if a transaction failed or not. I have this information > available in hidma_ll_status function for a limited amount of time until the > descriptor gets reused. > > > In that latter case do not use dma_async_is_complete() to check. You would > > need to store and report that cookie 'x' failed which you report status in > > .tx_statis() > > > > I really don't like the idea of telling 'hey client I finished your work and I > guarantee you it is complete. A month from now, by the way I actually didn't do > the work that day and I did not tell you' As i said previously, controllers cannot detect errors. In a system DMA burst may go bad due to various different issues which controller has not handle over. So from s system PoV we cannot declare success! > That's why, I preferred not to call the callback when I observe an error which I > think it makes more sense. That doesnt make sense. A client set a callback, it expect you to call one. The result quried maybe txn completed or error. Since you have means, please report.. > Where is the reliability in this? Some random bugs showing at random times. > I'd rather not call the callback and be safe. Especially, if you are talking about > servers; this is plain unacceptable. How does ignoring client wish caller solve this? You are really ona wrong path here. > As Lars-Peter and I indicated in my last email, I think we need to kill this > tx_status API and replace all the clients to use Dave's interface. It is practically > impossible to implement a reliable tx_status function. > > Once this transition happens, I can implement Dave's interface not before. > > Again, it will be a different patch than this one. I think v2 of this patch > needs to go in as it is. > > https://lkml.org/lkml/2016/7/31/64 I havent looked at the patch. If it is not invoking callback set by user, then I am not taking it. Sorry, we dont choose over client's wish. Thanks -- ~Vinod