Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A2A3EC433EF for ; Mon, 22 Nov 2021 15:16:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239828AbhKVPT3 convert rfc822-to-8bit (ORCPT ); Mon, 22 Nov 2021 10:19:29 -0500 Received: from aposti.net ([89.234.176.197]:41354 "EHLO aposti.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239771AbhKVPTY (ORCPT ); Mon, 22 Nov 2021 10:19:24 -0500 Date: Mon, 22 Nov 2021 15:16:06 +0000 From: Paul Cercueil Subject: Re: [PATCH 01/15] iio: buffer-dma: Get rid of incoming/outgoing queues To: Lars-Peter Clausen Cc: Jonathan Cameron , Alexandru Ardelean , Michael Hennerich , Sumit Semwal , Christian =?iso-8859-1?b?S/ZuaWc=?= , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org Message-Id: In-Reply-To: References: <20211115141925.60164-1-paul@crapouillou.net> <20211115141925.60164-2-paul@crapouillou.net> <0COX2R.BSNX3NW8N48T@crapouillou.net> <332d001d-8b5a-bba2-c490-ed2e5efd0b1d@metafoo.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Lars, Le lun., nov. 22 2021 at 16:08:51 +0100, Lars-Peter Clausen a ?crit : > On 11/21/21 9:08 PM, Paul Cercueil wrote: >> >> >> Le dim., nov. 21 2021 at 19:49:03 +0100, Lars-Peter Clausen >>  a ?crit : >>> On 11/21/21 6:52 PM, Paul Cercueil wrote: >>>> Hi Lars, >>>> >>>> Le dim., nov. 21 2021 at 17:23:35 +0100, Lars-Peter Clausen >>>>  a ?crit : >>>>> On 11/15/21 3:19 PM, Paul Cercueil wrote: >>>>>> The buffer-dma code was using two queues, incoming and outgoing, >>>>>> to >>>>>> manage the state of the blocks in use. >>>>>> >>>>>> While this totally works, it adds some complexity to the code, >>>>>> especially since the code only manages 2 blocks. It is much >>>>>> easier to >>>>>> just check each block's state manually, and keep a counter for >>>>>> the next >>>>>> block to dequeue. >>>>>> >>>>>> Since the new DMABUF based API wouldn't use these incoming and >>>>>> outgoing >>>>>> queues anyway, getting rid of them now makes the upcoming changes >>>>>> simpler. >>>>>> >>>>>> Signed-off-by: Paul Cercueil >>>>> The outgoing queue is going to be replaced by fences, but I think >>>>> we need to keep the incoming queue. >>>> >>>> Blocks are always accessed in sequential order, so we now have a >>>> "queue->next_dequeue" that cycles between the buffers >>>> allocated for fileio. >>>> >>>>>> [...] >>>>>> @@ -442,28 +435,33 @@ EXPORT_SYMBOL_GPL(iio_dma_buffer_disable); >>>>>> static void iio_dma_buffer_enqueue(struct iio_dma_buffer_queue >>>>>> *queue, >>>>>> struct iio_dma_buffer_block *block) >>>>>> { >>>>>> - if (block->state == IIO_BLOCK_STATE_DEAD) { >>>>>> + if (block->state == IIO_BLOCK_STATE_DEAD) >>>>>> iio_buffer_block_put(block); >>>>>> - } else if (queue->active) { >>>>>> + else if (queue->active) >>>>>> iio_dma_buffer_submit_block(queue, block); >>>>>> - } else { >>>>>> + else >>>>>> block->state = IIO_BLOCK_STATE_QUEUED; >>>>>> - list_add_tail(&block->head, &queue->incoming); >>>>> If iio_dma_buffer_enqueue() is called with a dmabuf and the >>>>> buffer is not active, it will be marked as queued, but we >>>>> don't actually keep a reference to it anywhere. It will >>>>> never be submitted to the DMA, and it will never be >>>>> signaled as completed. >>>> >>>> We do keep a reference to the buffers, in the queue->fileio.blocks >>>> array. When the buffer is enabled, all the blocks in that >>>> array that are in the "queued" state will be submitted to the >>>> DMA. >>>> >>> But not when used in combination with the DMA buf changes later in >>> this series. >>> >> >> That's still the case after the DMABUF changes of the series. Or can >> you point me exactly what you think is broken? >> > When you allocate a DMABUF with the allocate IOCTL and then submit it > with the enqueue IOCTL before the buffer is enabled it will end up > marked as queued, but not actually be queued anywhere. > Ok, it works for me because I never enqueue blocks before enabling the buffer. I can add a requirement that blocks must be enqueued only after the buffer is enabled. Cheers, -Paul