From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH] [RFC] dmaengine: add fifo_size member Date: Thu, 6 Jun 2019 17:32:37 +0100 Message-ID: <4b098fb6-1a5b-1100-ae16-978a887c9535@nvidia.com> References: <1556623828-21577-1-git-send-email-spujar@nvidia.com> <20190502060446.GI3845@vkoul-mobl.Dlink> <20190502122506.GP3845@vkoul-mobl.Dlink> <3368d1e1-0d7f-f602-5b96-a978fcf4d91b@nvidia.com> <20190504102304.GZ3845@vkoul-mobl.Dlink> <20190506155046.GH3845@vkoul-mobl.Dlink> <4cab47d0-41c3-5a87-48e1-d7f085c2e091@nvidia.com> <8a5b84db-c00b-fff4-543f-69d90c245660@nvidia.com> <3f836a10-eaf3-f59b-7170-6fe937cf2e43@ti.com> <4593f37c-5e89-8559-4e80-99dbfe4235de@nvidia.com> <50e1f9ed-1ea0-38f6-1a77-febd6a3a0848@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <50e1f9ed-1ea0-38f6-1a77-febd6a3a0848@gmail.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Dmitry Osipenko , Peter Ujfalusi , Sameer Pujar , Vinod Koul Cc: dan.j.williams@intel.com, tiwai@suse.com, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, sharadg@nvidia.com, rlokhande@nvidia.com, dramesh@nvidia.com, mkumard@nvidia.com, linux-tegra List-Id: linux-tegra@vger.kernel.org On 06/06/2019 16:18, Dmitry Osipenko wrote: ... >>> If I understood everything correctly, the FIFO buffer is shared among >>> all of the ADMA clients and hence it should be up to the ADMA driver to >>> manage the quotas of the clients. So if there is only one client that >>> uses ADMA at a time, then this client will get a whole FIFO buffer, but >>> once another client starts to use ADMA, then the ADMA driver will have >>> to reconfigure hardware to split the quotas. >> >> The FIFO quotas are managed by the ADMAIF driver (does not exist in >> mainline currently but we are working to upstream this) because it is >> this device that owns and needs to configure the FIFOs. So it is really >> a means to pass the information from the ADMAIF to the ADMA. > > So you'd want to reserve a larger FIFO for an audio channel that has a > higher audio rate since it will perform reads more often. You could also > prioritize one channel over the others, like in a case of audio call for > example. > > Is the shared buffer smaller than may be needed by clients in a worst > case scenario? If you could split the quotas statically such that each > client won't ever starve, then seems there is no much need in the > dynamic configuration. Actually, this is still very much relevant for the static case. Even if we defined a static configuration of the FIFO mapping in the ADMAIF driver we still need to pass this information to the ADMA. I don't really like the idea of having it statically defined in two different drivers. Jon -- nvpublic