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[92.176.231.205]) by smtp.gmail.com with ESMTPSA id n7-20020a05600c4f8700b0040588d85b3asm3908881wmq.15.2023.11.16.06.40.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Nov 2023 06:40:17 -0800 (PST) From: Javier Martinez Canillas To: Rob Herring Cc: linux-kernel@vger.kernel.org, Thomas Zimmermann , Ard Biesheuvel , Sima Vetter , dri-devel@lists.freedesktop.org, Andrew Worsley , Hector Martin , Sergio Lopez , Frank Rowand , devicetree@vger.kernel.org Subject: Re: [RFC PATCH] of/platform: Disable sysfb if a simple-framebuffer node is found In-Reply-To: References: <20231113085305.1823455-1-javierm@redhat.com> <87jzqi59bt.fsf@minerva.mail-host-address-is-not-set> Date: Thu, 16 Nov 2023 15:40:16 +0100 Message-ID: <87pm09223z.fsf@minerva.mail-host-address-is-not-set> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Rob Herring writes: > On Thu, Nov 16, 2023 at 3:36=E2=80=AFAM Javier Martinez Canillas > wrote: [...] >> > >> > This is the opposite of what we do for memory and memory reservations. >> > EFI is the source of truth for those. >> > >> > This could also lead to an interesting scenario. As simple-framebuffer >> > can define its memory in a /reserved-memory node, but that is ignored >> > in EFI boot. Probably would work, but only because EFI probably >> > generates its memory map table from the /reserved-memory nodes. >> > >> >> I see. So what would be the solution then? Ignoring creating a platform >> device for "simple-framebuffer" if booted using EFI and have an EFI-GOP? > > Shrug. I don't really know anything more about EFI FB, but I would > guess it can't support handling resources like clocks, power domains, > regulators, etc. that simple-fb can. So if a platform needs those, do That's correct, and the reason why I thought that the DTB would be the single source of truth for the firmware provided framebuffer. For example, in some arm platforms that u-boot does provide an EFI-GOP, you need to boot with clk_ignore_unused or the system framebuffer just goes away once the unused clocks are gated. Same for PD, regulators, etc. > we say they should not setup EFI-GOP? Or is there a use case for > having both? Clients that don't muck with resources can use EFI-GOP > and those that do use simple-fb. For example, does/can grub use > EFI-GOP, but not simple-fb? > I don't think grub can use the simple-fb, it can use the EFI-GOP if is available though. And things work because of course grub won't try to disable unused resources like Linux does. > Rob > --=20 Best regards, Javier Martinez Canillas Core Platforms Red Hat