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Message-ID: <0bae0df1-48ae-d02f-bce4-d1f69acf269e@redhat.com>
Date:   Fri, 20 May 2022 11:41:33 +0200
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Subject: Re: [PATCH V11 09/22] LoongArch: Add boot and setup routines
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To:     Ard Biesheuvel <ardb@kernel.org>,
        Huacai Chen <chenhuacai@loongson.cn>
Cc:     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>,
        Huacai Chen <chenhuacai@gmail.com>,
        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>
References: <20220518092619.1269111-1-chenhuacai@loongson.cn>
 <20220518092619.1269111-10-chenhuacai@loongson.cn>
 <CAMj1kXEBVWi2ZdR5Le5-G0DA43u-AMxmSO=pVt39qwN=PkzQfw@mail.gmail.com>
From:   Javier Martinez Canillas <javierm@redhat.com>
In-Reply-To: <CAMj1kXEBVWi2ZdR5Le5-G0DA43u-AMxmSO=pVt39qwN=PkzQfw@mail.gmail.com>
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Hello Ard and Huacai,

On 5/20/22 11:17, Ard Biesheuvel wrote:

[snip]

>> +
>> +static int __init register_gop_device(void)
>> +{
>> +       void *pd;
>> +
>> +       if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
>> +               return 0;
>> +       pd = platform_device_register_data(NULL, "efi-framebuffer", 0,
>> +                       &screen_info, sizeof(screen_info));
>> +       return PTR_ERR_OR_ZERO(pd);
>> +}
>> +subsys_initcall(register_gop_device);
> 
> Not sure this is now the correct way to do this - cc'ing Javier.
> 

Is not the correct way to do it indeed, that can just be dropped.

We have unified now all the system framebuffer platform device
registration under drivers/firmware/sysfb.c (and the EFI quirks
if needed under drivers/firmware/efi/sysfb_efi.c).

So the only thing that a platform should do, is to enable the
the CONFIG_SYSFB config option. The screen_info should be set
correctly from the EFI GOP, but it seems that's already working
since you were already using it in register_gop_device().

But also, the "efi-framebuffer" platform device matches against
the legacy efifb fbdev driver. And now there's a simpledrm driver
that is also able to use the firmware-provided framebuffer.

You can enable that driver with CONFIG_DRM_SIMPLEDRM.

That driver though doesn't match against "efi-framebuffer" but with
a "simple-framebuffer", to make sysfb register that instead of the
"efi-framebuffer" device, you need to set CONFIG_SYSFB_SIMPLEFB too.

If for some reasons you need to provide a fbdev interface to the
user-space, you can enable CONFIG_DRM_FBDEV_EMULATION to have that.

In summary, just enable the following to use the firmware framebuffer:

CONFIG_DRM_SIMPLEDRM=y
CONFIG_DRM_FBDEV_EMULATION=y
CONFIG_SYSFB=y
CONFIG_SYSFB_SIMPLEFB=y

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat