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 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 07999C433FE for ; Sun, 21 Nov 2021 20:08:50 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id F22C76E02B; Sun, 21 Nov 2021 20:08:48 +0000 (UTC) Received: from aposti.net (aposti.net [89.234.176.197]) by gabe.freedesktop.org (Postfix) with ESMTPS id CE0E46E02B for ; Sun, 21 Nov 2021 20:08:47 +0000 (UTC) Date: Sun, 21 Nov 2021 20:08:34 +0000 From: Paul Cercueil Subject: Re: [PATCH 01/15] iio: buffer-dma: Get rid of incoming/outgoing queues To: Lars-Peter Clausen Message-Id: In-Reply-To: <332d001d-8b5a-bba2-c490-ed2e5efd0b1d@metafoo.de> 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: quoted-printable X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michael Hennerich , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, Alexandru Ardelean , Christian =?iso-8859-1?b?S/ZuaWc=?= , Jonathan Cameron , linux-media@vger.kernel.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Le dim., nov. 21 2021 at 19:49:03 +0100, Lars-Peter Clausen=20 a =E9crit : > On 11/21/21 6:52 PM, Paul Cercueil wrote: >> Hi Lars, >>=20 >> Le dim., nov. 21 2021 at 17:23:35 +0100, Lars-Peter Clausen=20 >> =7F a =E9crit : >>> 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. >>>>=20 >>>> While this totally works, it adds some complexity to the code, >>>> especially since the code only manages 2 blocks. It is much easier=20 >>>> to >>>> just check each block's state manually, and keep a counter for the=20 >>>> next >>>> block to dequeue. >>>>=20 >>>> Since the new DMABUF based API wouldn't use these incoming and=20 >>>> outgoing >>>> queues anyway, getting rid of them now makes the upcoming changes >>>> simpler. >>>>=20 >>>> Signed-off-by: Paul Cercueil >>> The outgoing queue is going to be replaced by fences, but I think=20 >>> we =7F=7Fneed to keep the incoming queue. >>=20 >> Blocks are always accessed in sequential order, so we now have a=20 >> =7F"queue->next_dequeue" that cycles between the buffers allocated for=20 >> =7Ffileio. >>=20 >>>> [...] >>>> @@ -442,28 +435,33 @@ EXPORT_SYMBOL_GPL(iio_dma_buffer_disable); >>>> static void iio_dma_buffer_enqueue(struct iio_dma_buffer_queue=20 >>>> =7F=7F=7F*queue, >>>> struct iio_dma_buffer_block *block) >>>> { >>>> - if (block->state =3D=3D IIO_BLOCK_STATE_DEAD) { >>>> + if (block->state =3D=3D 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 =3D IIO_BLOCK_STATE_QUEUED; >>>> - list_add_tail(&block->head, &queue->incoming); >>> If iio_dma_buffer_enqueue() is called with a dmabuf and the buffer=20 >>> is =7F=7Fnot active, it will be marked as queued, but we don't actually= =20 >>> keep a =7F=7Freference to it anywhere. It will never be submitted to=20 >>> the DMA, and =7F=7Fit will never be signaled as completed. >>=20 >> We do keep a reference to the buffers, in the queue->fileio.blocks=20 >> =7Farray. When the buffer is enabled, all the blocks in that array=20 >> that =7Fare in the "queued" state will be submitted to the DMA. >>=20 > But not when used in combination with the DMA buf changes later in=20 > this series. >=20 That's still the case after the DMABUF changes of the series. Or can=20 you point me exactly what you think is broken? -Paul