From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Subject: Re: [PATCH v3] efifb: avoid reconfiguration of BAR that covers the framebuffer To: Ard Biesheuvel References: <1490196629-28088-1-git-send-email-ard.biesheuvel@linaro.org> <20170322193111.GA8190@wunner.de> <31da6db5-be22-9e84-5e76-67c519bc0b34@codeaurora.org> From: Sinan Kaya Message-ID: <704b8b8c-e607-29b3-e101-bbecd90073bb@codeaurora.org> Date: Wed, 22 Mar 2017 15:49:21 -0400 MIME-Version: 1.0 In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linux-efi@vger.kernel.org" , Matt Fleming , linux-pci , Peter Jones , Heyi Guo , Lukas Wunner , Hanjun Guo , Bjorn Helgaas , Lorenzo Pieralisi , Yinghai Lu , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+bjorn=helgaas.com@lists.infradead.org List-ID: On 3/22/2017 3:41 PM, Ard Biesheuvel wrote: >> As far as I know, kernel honors resource assignments done by the UEFI BIOS if >> they are correct. Kernel will reassign the resources only if something is wrong. >> > No, the kernel always reassigns all BARs on arm64. I think this is where the problem is. I'm not seeing this happen on QDF2400 which supports ACPI + UEFI BIOS combination only. I see that kernel honored the resources assigned by UEFI BIOS if I compare the BAR addresses. I see reassignment only when something is horribly broken. Then, there would be a bridge configuration invalid message in the boot log to confirm this. > >> Will this code break other platforms/architectures? >> > Which platforms/architectures are you referring to? EFIFB on a PCI > device is currently broken on arm64. In general or on your particular platform? > On x86, it works, given that BARs > are usually not reassigned, and so the patch should be a no-op in that > case (although I'd argue it is still an improvement to check whether > the device that owns the BAR actually has memory decoding enabled > before we attach the framebuffer driver to it) > I'm fine as long as it doesn't break anything. That's why, I'm asking. -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel