From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH v3 5/7] drm/sun4i: Rely on dma interconnect for our RAM offset Date: Tue, 5 Mar 2019 16:11:58 +0000 Message-ID: <7f089cc2-8d39-80e8-ee81-67372de618b8@arm.com> References: <16cb9f67-6b10-fbc3-6222-5364e718721b@arm.com> <20190213154144.5m5qxbfh2qmzwatn@flea> <5540eb65-d33c-ddca-8636-f567e84fb24a@arm.com> <20190219105551.hyq3nefz6iueyjt3@flea> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; Format="flowed" Content-Transfer-Encoding: base64 Return-path: In-Reply-To: <20190219105551.hyq3nefz6iueyjt3@flea> Content-Language: en-GB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" To: Maxime Ripard Cc: Mark Rutland , devicetree@vger.kernel.org, Yong Deng , Arnd Bergmann , Daniel Vetter , dri-devel@lists.freedesktop.org, Dave Martin , Paul Kocialkowski , Chen-Yu Tsai , Rob Herring , Thomas Petazzoni , Frank 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smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=sZRsEu0QmFpopERCa1CHD0u+nxMoEnz35LxD3gs+Scc=; b=DJmbvh6dS0d3sCY+yV2UcgA9O lySiJaHwNPcCS7q+4yr/NUOirX5sB7MskmTUAHTKUHLi5FM5YGMfMC1Wl/yEtk4iudM1rYmqHZvRX Cg1A0TN1nxap4Ge1majFB1sPSKyonag0p4kXBXZTYYh9E2g777SqDxj1Lolr448NinO7yPz8m/sru 1/LnqwQeV7JgezCLU+Vy2Ur5lI1Vf9y4m3n7SWSF5XJ5L946WZXDMgm+aIw9lA9Ry99RhGtmuNQXG bbgFm3XOCskp45st6jH4qpkdaJ2oTmKcw38XBal6CUr2ASScFO9jrOIIcwQR3cVm6dgU1i0HLYhw0 qx/HnSEuA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h1Cfm-0001TC-Fw; Tue, 05 Mar 2019 16:12:06 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h1Cfi-0001S5-Qr for linux-arm-kernel@lists.infradead.org; Tue, 05 Mar 2019 16:12:04 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8151FEBD; Tue, 5 Mar 2019 08:12:02 -0800 (PST) Received: from [10.1.196.75] (e110467-lin.cambridge.arm.com [10.1.196.75]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 20A6F3F703; Tue, 5 Mar 2019 08:11:59 -0800 (PST) Subject: Re: [PATCH v3 5/7] drm/sun4i: Rely on dma interconnect for our RAM offset To: Maxime Ripard References: <16cb9f67-6b10-fbc3-6222-5364e718721b@arm.com> <20190213154144.5m5qxbfh2qmzwatn@flea> <5540eb65-d33c-ddca-8636-f567e84fb24a@arm.com> <20190219105551.hyq3nefz6iueyjt3@flea> From: Robin Murphy Message-ID: <7f089cc2-8d39-80e8-ee81-67372de618b8@arm.com> Date: Tue, 5 Mar 2019 16:11:58 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190219105551.hyq3nefz6iueyjt3@flea> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190305_081202_880688_86166291 X-CRM114-Status: GOOD ( 34.00 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , devicetree@vger.kernel.org, Yong Deng , Arnd Bergmann , Daniel Vetter , dri-devel@lists.freedesktop.org, Dave Martin , Paul Kocialkowski , Chen-Yu Tsai , Rob Herring , Thomas Petazzoni , Frank Rowand , Georgi Djakov , linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 19/02/2019 10:55, Maxime Ripard wrote: > Hi Robin, > > On Wed, Feb 13, 2019 at 04:40:11PM +0000, Robin Murphy wrote: >> On 13/02/2019 15:41, Maxime Ripard wrote: >>> Hi Robin, >>> >>> Thanks for your feedback! >>> >>> On Tue, Feb 12, 2019 at 06:46:40PM +0000, Robin Murphy wrote: >>>> On 11/02/2019 15:02, Maxime Ripard wrote: >>>>> Now that we can express our DMA topology, rely on those property instead of >>>>> hardcoding an offset from the dma_addr_t which wasn't really great. >>>>> >>>>> We still need to add some code to deal with the old DT that would lack that >>>>> property, but we move the offset to the DRM device dma_pfn_offset to be >>>>> able to rely on just the dma_addr_t associated to the GEM object. >>>>> >>>>> Acked-by: Daniel Vetter >>>>> Signed-off-by: Maxime Ripard >>>>> --- >>>>> drivers/gpu/drm/sun4i/sun4i_backend.c | 28 +++++++++++++++++++++------- >>>>> 1 file changed, 21 insertions(+), 7 deletions(-) >>>>> >>>>> diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c >>>>> index 9e9255ee59cd..1846a1b30fea 100644 >>>>> --- a/drivers/gpu/drm/sun4i/sun4i_backend.c >>>>> +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c >>>>> @@ -383,13 +383,6 @@ int sun4i_backend_update_layer_buffer(struct sun4i_backend *backend, >>>>> paddr = drm_fb_cma_get_gem_addr(fb, state, 0); >>>>> DRM_DEBUG_DRIVER("Setting buffer address to %pad\n", &paddr); >>>>> - /* >>>>> - * backend DMA accesses DRAM directly, bypassing the system >>>>> - * bus. As such, the address range is different and the buffer >>>>> - * address needs to be corrected. >>>>> - */ >>>>> - paddr -= PHYS_OFFSET; >>>>> - >>>>> if (fb->format->is_yuv) >>>>> return sun4i_backend_update_yuv_buffer(backend, fb, paddr); >>>>> @@ -835,6 +828,27 @@ static int sun4i_backend_bind(struct device *dev, struct device *master, >>>>> dev_set_drvdata(dev, backend); >>>>> spin_lock_init(&backend->frontend_lock); >>>>> + if (of_find_property(dev->of_node, "interconnects", NULL)) { >>>>> + /* >>>>> + * This assume we have the same DMA constraints for all our the >>>>> + * devices in our pipeline (all the backends, but also the >>>>> + * frontends). This sounds bad, but it has always been the case >>>>> + * for us, and DRM doesn't do per-device allocation either, so >>>>> + * we would need to fix DRM first... >>>>> + */ >>>>> + ret = of_dma_configure(drm->dev, dev->of_node, true); >>>> >>>> It would be even nicer if we could ensure that drm->dev originates from a DT >>>> node which has the appropriate interconnects property itself, such that we >>>> can assume it's already configured correctly. >>> >>> The thing is drm->dev comes from a node in the DT that is a virtual >>> node, and therefore doesn't have any resources attached, so I'm not >>> sure we have any other way, unfortunately. >> >> Right, I appreciate that it may not be feasible to swizzle drm->dev for one >> of the 'real' component devices, but what I was also thinking was that since >> the virtual device node effectively represents the aggregation of the other >> component devices, we could just say that it also has to have its own link >> to the MBUS interconnect (with the ID of the pipeline entrypoint it's >> associated with, I guess). That ought to be enough to get dma_configure() to >> do the job, and in fairness is no *less* accurate a description of the >> hardware, even if might look a little funky to some. > > That virtual device however can work with up to 4 devices that can > perform DMA operations, all of them going through a different port of > the MBUS controller that can account for DMA usage on a per-master > basis. > > Eventually, we should support that feature as well, but the point is > that from a DT point of view, there's not a single point of DMA access > for that particular device but more likely 2-4 points, each with a > different argument to the phandle. > > We could of course have a hack and use only one of them, but that > would be less accurate than what we currently have. Plus, this is > really due to a restriction on the DRM side, that could change in the > future (even though it's unlikely). Fixing that restriction would make > that property completely useless, confusing and wrong from an hardware > PoV. Thanks for the clarification. Much as I'd like to keep of_dma_configure() out of drivers as much as possible, I agree that it's not sufficient justification for (ab)using DT to sidestep a Linux-specific issue which might eventually get properly fixed anyway. I'm sure the last thing sunxi needs is any more awkward DT ABI concerns :) Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel