From: Huacai Chen <chenhuacai@gmail.com>
To: Javier Martinez Canillas <javierm@redhat.com>
Cc: Ard Biesheuvel <ardb@kernel.org>,
Huacai Chen <chenhuacai@loongson.cn>,
Arnd Bergmann <arnd@arndb.de>, Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
David Airlie <airlied@linux.ie>, Jonathan Corbet <corbet@lwn.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-arch <linux-arch@vger.kernel.org>,
Linux Doc Mailing List <linux-doc@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Xuefeng Li <lixuefeng@loongson.cn>,
Yanteng Si <siyanteng@loongson.cn>, Guo Ren <guoren@kernel.org>,
Xuerui Wang <kernel@xen0n.name>,
Jiaxun Yang <jiaxun.yang@flygoat.com>,
Stephen Rothwell <sfr@canb.auug.org.au>,
linux-efi <linux-efi@vger.kernel.org>
Subject: Re: [PATCH V11 09/22] LoongArch: Add boot and setup routines
Date: Sat, 21 May 2022 15:37:30 +0800 [thread overview]
Message-ID: <CAAhV-H4UxkyHr=NQGFAAjCXwXHXDLsN_CV-tSCn6oonOSSjb0A@mail.gmail.com> (raw)
In-Reply-To: <859d5489-9361-3db0-1da4-1417ed2fad6c@redhat.com>
Hi, Javier,
On Sat, May 21, 2022 at 3:07 PM Javier Martinez Canillas
<javierm@redhat.com> wrote:
>
> Hello Huacai,
>
> On 5/21/22 03:40, Huacai Chen wrote:
> > Hi, Javier,
>
> [snip]
>
> >>>> Conversely, if the sysfb_init() is executed first then the platform device
> >>>> will be registered and latter when the driver's init register the driver
> >>>> this will match the already registered device.
> >>> Yes, you are right, my consideration is too complex. The only real
> >>> problem is a harmless error "efifb: a framebuffer is already
> >>> registered" when both efifb and the native display driver are
> >>> built-in.
> >>>
> >>
> >> But this shouldn't be a problem if you drop your register_gop_device() that
> >> registers an "efi-framebuffer", since sysfb would either register a platform
> >> device "simple-framebufer" or "efi-framebuffer", but never both. Those are
> >> mutually exclusive.
> >>
> >> I think what's happening now is that sysfb is registering a "simple-framebuffer"
> >> but your register_gop_device() function is also registering an "efi-framebuffer".
> > No, I have already removed register_gop_device(). Now my problem is like this:
> > 1, efifb (or simpledrm) is built-in;
> > 2, a native display driver (such as radeon) is also built-in.
> >
>
> Ah, I see. The common configuration is for the firmware-provide framebuffer
> drivers ({efi,simple}fb,simpledrm,etc) to be built-in and native drivers to
> be built as a module.
>
> > Because efifb, radeon and sysfb are all in device_initcall() level,
> > the order in practise is like this:
> >
> > efifb registered at first, but no "efi-framebuffer" device yet.
> > radeon registered later, and /dev/fb0 created.
> > sysfb_init() comes at last, it registers "efi-framebuffer" and then
> > causes the error "efifb: a framebuffer is already registered".
>
> Yes, this is problem because only conflicting framebuffers and associated
> devices are unregistered when a real driver is registered, but no devices
> that have not matched with drivers and registered framebuffers or disable
> devices to be registered later.
>
> I proposed the following patch series but the conclusion was that this has
> to be fixed in a more general way:
>
> https://lore.kernel.org/lkml/20220511112438.1251024-1-javierm@redhat.com/
>
> > make sysfb_init() to be subsys_initcall_sync() can avoid this.
> >
>
> Right, now I understand your problem and you are correct that this will
> avoid it. But I believe is just papering over the issue, the problem is
> that if a native fbdev or DRM driver probed, then sysfb (or any other
> platform code) should not register a device to match a driver that will
> attempt to use a firmware-provided framebuffer.
>
> A problem with moving to subsys_initcall_sync() is that this will delay
> more when a display is available in the system, and just to cope up with
> a corner case (as mentioned the common case is native drivers as module).
OK, your method seems better, but I think moving to
subsys_initcall_sync() can make the screen display as early as
possible.
Huacai
> --
> Best regards,
>
> Javier Martinez Canillas
> Linux Engineering
> Red Hat
>
next prev parent reply other threads:[~2022-05-21 7:37 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-18 9:25 [PATCH V11 00/22] arch: Add basic LoongArch support Huacai Chen
2022-05-18 9:25 ` [PATCH V11 01/22] Documentation: LoongArch: Add basic documentations Huacai Chen
2022-05-18 15:34 ` WANG Xuerui
2022-05-18 9:25 ` [PATCH V11 02/22] Documentation/zh_CN: Add basic LoongArch documentations Huacai Chen
2022-05-18 15:32 ` WANG Xuerui
2022-05-20 7:37 ` Guo Ren
2022-05-20 7:43 ` WANG Xuerui
2022-05-18 9:26 ` [PATCH V11 03/22] LoongArch: Add ELF-related definitions Huacai Chen
2022-05-18 9:26 ` [PATCH V11 04/22] LoongArch: Add writecombine support for drm Huacai Chen
2022-05-18 9:26 ` [PATCH V11 05/22] LoongArch: Add build infrastructure Huacai Chen
2022-05-18 15:22 ` WANG Xuerui
2022-05-20 7:25 ` Guo Ren
2022-05-18 9:26 ` [PATCH V11 06/22] LoongArch: Add CPU definition headers Huacai Chen
2022-05-18 15:45 ` WANG Xuerui
2022-05-18 16:12 ` Huacai Chen
2022-05-18 9:26 ` [PATCH V11 07/22] LoongArch: Add atomic/locking headers Huacai Chen
2022-05-18 15:54 ` WANG Xuerui
2022-05-20 7:54 ` Guo Ren
2022-05-20 9:50 ` Huacai Chen
2022-05-20 18:14 ` Guo Ren
2022-05-21 1:55 ` Huacai Chen
2022-05-18 9:26 ` [PATCH V11 08/22] LoongArch: Add other common headers Huacai Chen
2022-05-18 16:04 ` WANG Xuerui
2022-05-18 9:26 ` [PATCH V11 09/22] LoongArch: Add boot and setup routines Huacai Chen
2022-05-18 15:17 ` WANG Xuerui
2022-05-18 16:08 ` Huacai Chen
2022-05-20 9:17 ` Ard Biesheuvel
2022-05-20 9:41 ` Javier Martinez Canillas
2022-05-20 14:09 ` Huacai Chen
2022-05-20 14:23 ` Javier Martinez Canillas
2022-05-20 15:19 ` Huacai Chen
2022-05-20 16:32 ` Javier Martinez Canillas
2022-05-21 1:40 ` Huacai Chen
2022-05-21 7:06 ` Javier Martinez Canillas
2022-05-21 7:37 ` Huacai Chen [this message]
2022-05-21 9:06 ` Javier Martinez Canillas
2022-05-21 9:13 ` Huacai Chen
2022-05-21 9:43 ` Javier Martinez Canillas
2022-05-20 15:53 ` Huacai Chen
2022-05-24 8:27 ` Xi Ruoyao
2022-05-24 10:59 ` Huacai Chen
2022-05-24 12:48 ` 李超
2022-05-18 9:26 ` [PATCH V11 10/22] LoongArch: Add exception/interrupt handling Huacai Chen
2022-05-18 9:26 ` [PATCH V11 11/22] LoongArch: Add process management Huacai Chen
2022-05-18 9:26 ` [PATCH V11 12/22] LoongArch: Add memory management Huacai Chen
2022-05-18 9:26 ` [PATCH V11 13/22] LoongArch: Add system call support Huacai Chen
2022-05-18 9:26 ` [PATCH V11 14/22] LoongArch: Add signal handling support Huacai Chen
2022-05-18 16:13 ` WANG Xuerui
2022-05-18 16:39 ` Eric W. Biederman
2022-05-18 16:54 ` Huacai Chen
2022-05-18 17:17 ` WANG Xuerui
2022-05-18 9:26 ` [PATCH V11 15/22] LoongArch: Add ELF and module support Huacai Chen
2022-05-18 9:26 ` [PATCH V11 16/22] LoongArch: Add misc common routines Huacai Chen
2022-05-18 9:57 ` [PATCH V11 17/22] LoongArch: Add some library functions Huacai Chen
2022-05-18 9:57 ` [PATCH V11 18/22] LoongArch: Add PCI controller support Huacai Chen
2022-05-18 9:57 ` [PATCH V11 19/22] LoongArch: Add VDSO and VSYSCALL support Huacai Chen
2022-05-18 9:57 ` [PATCH V11 20/22] LoongArch: Add multi-processor (SMP) support Huacai Chen
2022-05-18 9:57 ` [PATCH V11 21/22] LoongArch: Add Non-Uniform Memory Access (NUMA) support Huacai Chen
2022-05-18 9:57 ` [PATCH V11 22/22] LoongArch: Add Loongson-3 default config file Huacai Chen
2022-05-18 13:42 ` [PATCH V11 00/22] arch: Add basic LoongArch support Arnd Bergmann
2022-05-18 17:18 ` Huacai Chen
2022-05-18 22:36 ` Stephen Rothwell
2022-05-22 4:18 ` WANG Xuerui
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