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from ziggy.stardust ([37.223.145.235]) by smtp.gmail.com with ESMTPSA id k11sm2677479ejr.3.2019.09.12.10.18.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Sep 2019 10:18:33 -0700 (PDT) Subject: Re: [PATCH v5 0/4] Raspberry Pi 4 DMA addressing support To: Matthias Brugger , Stefan Wahren , catalin.marinas@arm.com, marc.zyngier@arm.com, robh+dt@kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-riscv@lists.infradead.org, hch@lst.de, Nicolas Saenz Julienne Cc: f.fainelli@gmail.com, robin.murphy@arm.com, linux-kernel@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, phill@raspberrypi.org, will@kernel.org, m.szyprowski@samsung.com References: <20190909095807.18709-1-nsaenzjulienne@suse.de> <5a8af6e9-6b90-ce26-ebd7-9ee626c9fa0e@gmx.net> <3f9af46e-2e1a-771f-57f2-86a53caaf94a@suse.com> From: Matthias Brugger Openpgp: preference=signencrypt Autocrypt: addr=matthias.bgg@gmail.com; prefer-encrypt=mutual; keydata= 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<09f82f88-a13a-b441-b723-7bb061a2f1e3@gmail.com> Date: Thu, 12 Sep 2019 19:18:31 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <3f9af46e-2e1a-771f-57f2-86a53caaf94a@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 10/09/2019 11:27, Matthias Brugger wrote: >=20 >=20 > On 09/09/2019 21:33, Stefan Wahren wrote: >> Hi Nicolas, >> >> Am 09.09.19 um 11:58 schrieb Nicolas Saenz Julienne: >>> Hi all, >>> this series attempts to address some issues we found while bringing u= p >>> the new Raspberry Pi 4 in arm64 and it's intended to serve as a follo= w >>> up of these discussions: >>> v4: https://lkml.org/lkml/2019/9/6/352 >>> v3: https://lkml.org/lkml/2019/9/2/589 >>> v2: https://lkml.org/lkml/2019/8/20/767 >>> v1: https://lkml.org/lkml/2019/7/31/922 >>> RFC: https://lkml.org/lkml/2019/7/17/476 >>> >>> The new Raspberry Pi 4 has up to 4GB of memory but most peripherals c= an >>> only address the first GB: their DMA address range is >>> 0xc0000000-0xfc000000 which is aliased to the first GB of physical >>> memory 0x00000000-0x3c000000. Note that only some peripherals have th= ese >>> limitations: the PCIe, V3D, GENET, and 40-bit DMA channels have a wid= er >>> view of the address space by virtue of being hooked up trough a secon= d >>> interconnect. >>> >>> Part of this is solved on arm32 by setting up the machine specific >>> '.dma_zone_size =3D SZ_1G', which takes care of reserving the coheren= t >>> memory area at the right spot. That said no buffer bouncing (needed f= or >>> dma streaming) is available at the moment, but that's a story for >>> another series. >>> >>> Unfortunately there is no such thing as 'dma_zone_size' in arm64. Onl= y >>> ZONE_DMA32 is created which is interpreted by dma-direct and the arm6= 4 >>> arch code as if all peripherals where be able to address the first 4G= B >>> of memory. >>> >>> In the light of this, the series implements the following changes: >>> >>> - Create both DMA zones in arm64, ZONE_DMA will contain the first 1G >>> area and ZONE_DMA32 the rest of the 32 bit addressable memory. So f= ar >>> the RPi4 is the only arm64 device with such DMA addressing limitati= ons >>> so this hardcoded solution was deemed preferable. >>> >>> - Properly set ARCH_ZONE_DMA_BITS. >>> >>> - Reserve the CMA area in a place suitable for all peripherals. >>> >>> This series has been tested on multiple devices both by checking the >>> zones setup matches the expectations and by double-checking physical >>> addresses on pages allocated on the three relevant areas GFP_DMA, >>> GFP_DMA32, GFP_KERNEL: >>> >>> - On an RPi4 with variations on the ram memory size. But also forcing >>> the situation where all three memory zones are nonempty by setting = a 3G >>> ZONE_DMA32 ceiling on a 4G setup. Both with and without NUMA suppor= t. >>> >> i like to test this series on Raspberry Pi 4 and i have some questions >> to get arm64 running: >> >> Do you use U-Boot? Which tree? >=20 > If you want to use U-Boot, try v2019.10-rc4, it should have everything = you need > to boot your kernel. >=20 Ok, here is a thing. In the linux kernel we now use bcm2711 as SoC name, = but the RPi4 devicetree provided by the FW uses mostly bcm2838. U-Boot in its def= ault config uses the devicetree provided by the FW, mostly because this way yo= u don't have to do anything to find out how many RAM you really have. Secondly be= cause this will allow us, in the near future, to have one U-boot binary for bot= h RPi3 and RPi4 (and as a side effect one binary for RPi1 and RPi2). Anyway, I found at least, that the following compatibles need to be added= : "brcm,bcm2838-cprman" "brcm,bcm2838-gpio" Without at least the cprman driver update, you won't see anything. "brcm,bcm2838-rng200" is also a candidate. I also suppose we will need to add "brcm,bcm2838" to arch/arm/mach-bcm/bcm2711.c, but I haven't verified this. Regards, Matthias > Regards, > Matthias >=20 >> Are there any config.txt tweaks necessary? >> >> >=20 > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >=20