From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: dma: add support for reporting pause and resume separately From: Andy Shevchenko Message-Id: Date: Wed, 4 Jul 2018 13:38:58 +0300 To: Vinod Cc: Marek Szyprowski , Mark Brown , Lars-Peter Clausen , dmaengine , ALSA Development Mailing List , Linux Kernel Mailing List , Dan Williams , Bartlomiej Zolnierkiewicz List-ID: T24gV2VkLCBKdWwgNCwgMjAxOCBhdCAxMDowMCBBTSwgVmlub2QgPHZrb3VsQGtlcm5lbC5vcmc+ IHdyb3RlOgo+IEhpIE1hcmVrLAo+Cj4gT24gMDItMDctMTgsIDE1OjA4LCBNYXJlayBTenlwcm93 c2tpIHdyb3RlOgo+PiAnY21kX3BhdXNlJyBETUEgY2hhbm5lbCBjYXBhYmlsaXR5IG1lYW5zIHRo YXQgcmVzcGVjdGl2ZSBETUEgZW5naW5lCj4+IHN1cHBvcnRzIGJvdGggcGF1c2luZyBhbmQgcmVz dW1pbmcgZ2l2ZW4gRE1BIGNoYW5uZWwuIEhvd2V2ZXIsIGluIHNvbWUKPj4gY2FzZXMgaXQgaXMg aW1wb3J0YW50IHRvIGtub3cgaWYgRE1BIGNoYW5uZWwgY2FuIGJlIHBhdXNlZCB3aXRob3V0IHRo ZQo+PiBuZWVkIHRvIHJlc3VtZSBpdC4gVGhpcyBpcyBhIHR5cGljYWwgcmVxdWlyZW1lbnQgZm9y IHByb3BlciByZXNpZHVlCj4+IHJlYWRpbmcgb24gdHJhbnNmZXIgdGltZW91dCBpbiBVQVJUIGRy aXZlcnMuIFRoZXJlIGFyZSBhbHNvIHNvbWUgRE1BCj4+IGVuZ2luZXMgd2l0aCBsaW1pdGVkIGhh cmR3YXJlLCB3aGljaCBkb2Vzbid0IHJlYWxseSBzdXBwb3J0IHJlc3VtaW5nLgo+Cj4gQW0gY3Vy aW91cyBnaXZlbiB0aGF0IHlvdXIgaGFyZHdhcmUgZG9lcyBub3Qgc3VwcG9ydCByZXN1bWUsIHdo YXQgd2FzIG1vdGl2YXRpb24KPiBmb3IgYWRkaW5nIHBhdXNlPwo+Cj4+IFJlcG9ydGluZyBwYXVz ZSBhbmQgcmVzdW1lIGNhcGFiaWxpdGllcyBzZXBhcmF0ZWx5IGFsbG93cyBVQVJUIGRyaXZlcnMg dG8KPj4gcHJvcGVybHkgY2hlY2sgZm9yIHRoZSByZWFsbHkgcmVxdWlyZWQgY2FwYWJpbGl0aWVz IGFuZCBvcGVyYXRlIGluIERNQQo+PiBtb2RlIGFsc28gaW4gc3lzdGVtcyB3aXRoIGxpbWl0ZWQg RE1BIGhhcmR3YXJlLiBPbiB0aGUgb3RoZXIgaGFuZCBkcml2ZXJzLAo+PiB3aGljaCByZWx5IG9u IGZ1bGwgY2hhbm5lbCBzdXNwZW5kL3Jlc3VtZSBzdXBwb3J0LCBzaG91bGQgbm93IGNoZWNrIGZv cgo+PiBib3RoICdwYXVzZScgYW5kICdyZXN1bWUnIGZlYXR1cmVzLgo+Pgo+PiBFeGlzdGluZyBj bGllbnRzIG9mIGRtYV9nZXRfc2xhdmVfY2FwcygpIGhhdmUgYmVlbiBjaGVja2VkIGFuZCB0aGUg b25seQo+PiBkcml2ZXIgd2hpY2ggcmVseSBvbiBwcm9wZXIgY2hhbm5lbCByZXN1bWluZyBpcyBz b2MtZ2VuZXJpYy1kbWFlbmdpbmUtcGNtCj4+IGRyaXZlciwgd2hpY2ggaGFzIGJlZW4gdXBkYXRl ZCB0byBjaGVjayB0aGUgbmV3bHkgYWRkZWQgY2FwYWJpbGl0eS4KPj4gRXhpc3RpbmcgJ2NtZF9w YXVzZScgbm93IG9ubHkgaW5kaWNhdGVzIHRoYXQgRE1BIGVuZ2luZSBzdXBwb3J0IHBhdXNpbmcK Pj4gZ2l2ZW4gRE1BIGNoYW5uZWwuCj4KPiBUaGUgY2hhbmdlIGxvb2tzIGZpbmUgdG8gbWUuIEkg d2FzIGhvcGluZyB0aGF0IHNlcmlhbCB3b3VsZCBhbHNvIGNoZWNrCj4gdGhpcy4uCgpBRkFJVSBz ZXJpYWwgZG9lcyBub3QgbmVlZCB0byByZXN1bWUuCg== From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ADFFCC3279B for ; 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Wed, 04 Jul 2018 03:38:59 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a67:2149:0:0:0:0:0 with HTTP; Wed, 4 Jul 2018 03:38:58 -0700 (PDT) In-Reply-To: <20180704070033.GA22377@vkoul-mobl> References: <20180702130819eucas1p2e11d8fabec93ba78d9e84f4ca6e5fd65~9jzNWZMqQ1216712167eucas1p27@eucas1p2.samsung.com> <20180704070033.GA22377@vkoul-mobl> From: Andy Shevchenko Date: Wed, 4 Jul 2018 13:38:58 +0300 Message-ID: Subject: Re: [PATCH] dma: add support for reporting pause and resume separately To: Vinod Cc: Marek Szyprowski , Mark Brown , Lars-Peter Clausen , dmaengine , ALSA Development Mailing List , Linux Kernel Mailing List , Dan Williams , Bartlomiej Zolnierkiewicz Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 4, 2018 at 10:00 AM, Vinod wrote: > Hi Marek, > > On 02-07-18, 15:08, Marek Szyprowski wrote: >> 'cmd_pause' DMA channel capability means that respective DMA engine >> supports both pausing and resuming given DMA channel. However, in some >> cases it is important to know if DMA channel can be paused without the >> need to resume it. This is a typical requirement for proper residue >> reading on transfer timeout in UART drivers. There are also some DMA >> engines with limited hardware, which doesn't really support resuming. > > Am curious given that your hardware does not support resume, what was motivation > for adding pause? > >> Reporting pause and resume capabilities separately allows UART drivers to >> properly check for the really required capabilities and operate in DMA >> mode also in systems with limited DMA hardware. On the other hand drivers, >> which rely on full channel suspend/resume support, should now check for >> both 'pause' and 'resume' features. >> >> Existing clients of dma_get_slave_caps() have been checked and the only >> driver which rely on proper channel resuming is soc-generic-dmaengine-pcm >> driver, which has been updated to check the newly added capability. >> Existing 'cmd_pause' now only indicates that DMA engine support pausing >> given DMA channel. > > The change looks fine to me. I was hoping that serial would also check > this.. AFAIU serial does not need to resume. -- With Best Regards, Andy Shevchenko