linux-kernel - Re: [PATCH V11 09/22] LoongArch: Add boot and setup routines

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Date:   Sat, 21 May 2022 09:40:14 +0800
From:   Huacai Chen <chenhuacai@...il.com>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     Ard Biesheuvel <ardb@...nel.org>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Airlie <airlied@...ux.ie>,
        Jonathan Corbet <corbet@....net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Yanteng Si <siyanteng@...ngson.cn>,
        Guo Ren <guoren@...nel.org>, Xuerui Wang <kernel@...0n.name>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [PATCH V11 09/22] LoongArch: Add boot and setup routines

Hi, Javier,

On Sat, May 21, 2022 at 12:32 AM Javier Martinez Canillas
<javierm@...hat.com> wrote:
>
> On 5/20/22 17:19, 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.

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".
make sysfb_init() to be subsys_initcall_sync() can avoid this.

Huacai

>
> --
> Best regards,
>
> Javier Martinez Canillas
> Linux Engineering
> Red Hat
>