From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: Re: [PATCH] dma: omap-dma: add support for pause of non-cyclic transfers Date: Fri, 07 Aug 2015 15:42:06 +0200 Message-ID: <55C4B5AE.10309@linutronix.de> References: <1438936917-7254-1-git-send-email-bigeasy@linutronix.de> <55C47DE1.9020902@ti.com> <55C48A1E.3070007@linutronix.de> <20150807132241.GN7576@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20150807132241.GN7576@n2100.arm.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org To: Russell King - ARM Linux Cc: Peter Ujfalusi , Vinod Koul , Dan Williams , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, nsekhar@ti.com, linux-omap@vger.kernel.org, linux-serial@vger.kernel.org, john.ogness@linutronix.de List-Id: linux-omap@vger.kernel.org On 08/07/2015 03:22 PM, Russell King - ARM Linux wrote: > On Fri, Aug 07, 2015 at 12:36:14PM +0200, Sebastian Andrzej Siewior wrote: >> On 08/07/2015 11:44 AM, Peter Ujfalusi wrote: >>> with a short testing audio did not broke (the only user of pause/resume) >>> Some comments embedded. >>> >>>> Cc: >>> >>> Why stable? This is not fixing any bugs since the PAUSE was not allowed for >>> non cyclic transfers. >> >> Hmmm. The DRA7x was using pause before for UART. I just did not see it >> coming that it was not allowed here. John made a similar change to the >> edma driver and I assumed it went stable but now I see that it was just >> cherry-picked into the ti tree. > > This is *NOT* stable material. > > Pause of these channels is something that omap-dma has *never* supported. > Therefore, it is *not* a regression. What you are doing is *adding* a > feature to the omap-dma driver. That is not stable material in any sense. > Stable is for bug fixes to existing code, not feature enhancements. I didn't consider this as a feature. > If something else has been converted to pause channels and that is causing > a problem, then _that_ conversion is where the bug lies, not the lack of > support in the omap-dma. So we had the 8250-DMA doing pause and all its current users implement it. We have a DMA driver tree which is not used and it not implementing pause (not implementing pause at all). Later we get a combo of 8250-DMA + DMA driver that is broken because the lack of pause and this is noticed a few kernel releases later. The only way of fixing the bug is by implementing the pause feature. Now you are saying that even if I implement this missing feature in a newer kernel I am not allowed to mark it stable despite the fact that it fixes an existing problem in older kernels because it is not a regression. > If it's a result of using some new driver with omap-dma, then the problem > is with whatever introduced that new combination - it's not that omap-dma > is buggy. > > Don't fix bugs in -stable by adding features. That's _no_ way to fix bugs. > > NAK on this feature patch having any kind of stable tag. I already accepted this. Sebastian