linux-kernel - Re: [PATCH] simpldrm: Enable boot time VESA graphic mode selection.

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Message-ID: <14dd85f1-21b1-2ff7-3491-466c077210e6@suse.de>
Date:   Fri, 18 Feb 2022 11:24:39 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Michal Suchánek <msuchanek@...e.de>
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        David Airlie <airlied@...ux.ie>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Sam Ravnborg <sam@...nborg.org>,
        Helge Deller <deller@....de>, x86@...nel.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Arnd Bergmann <arnd@...db.de>,
        Borislav Petkov <bp@...en8.de>,
        Maxime Ripard <maxime@...no.tech>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Martin Mares <mj@....cz>,
        linux-video@...ey.karlin.mff.cuni.cz,
        Daniel Mack <daniel@...que.org>
Subject: Re: [PATCH] simpldrm: Enable boot time VESA graphic mode selection.

Hi

Am 18.02.22 um 11:08 schrieb Michal Suchánek:
> Hello,
> 
> On Fri, Feb 18, 2022 at 10:57:33AM +0100, Thomas Zimmermann wrote:
>> Hi Michal
>>
>> Am 18.02.22 um 10:33 schrieb Michal Suchanek:
>>> Since switch to simpledrm VESA graphic modes are no longer available
>>> with legacy BIOS.
>>>
>>> The x86 realmode boot code enables the VESA graphic modes when option
>>> FB_BOOT_VESA_SUPPORT is enabled.
>>>
>>> To enable use of VESA modes with simpledrm in legacy BIOS boot mode drop
>>> dependency of BOOT_VESA_SUPPORT on FB, also drop the FB_ prefix, and
>>> select the option when simpledrm is built-in on x86.
>>
>> Thanks for sending the patch.
>>
>> I tested simpledrm on a VESA-based systems and it work. Do you have a
> 
> In EFI or legacy mode?

It was a 32-bit AthlonXP. So as legacy as it gets.

> 
>> concrete example of a mode that doesn't work any longer?
> 
> As per discussion in
> https://bugzilla.opensuse.org/show_bug.cgi?id=1193250 vga=791 does not.

I wonder if this fixes a few more of the complains we've seen about 
missing resolutions.

> 
> Also it is clear examinig the realmode code that this option is needed
> to enable graphic mode selection.
> 
> I don't have a system with legacy BIOS at hand but from user testing
> this improves the situation - kernel does not reeject the videomode
> argument, and simpledrm is initialized during boot.

No doubt about that.

Best regards
Thomas

> 
> Thanks
> 
> Michal
> 
>>
>>>
>>> Fixes: 11e8f5fd223b ("drm: Add simpledrm driver")
>>> Signed-off-by: Michal Suchanek <msuchanek@...e.de>
>>> ---
>>>    arch/x86/boot/video-vesa.c   | 4 ++--
>>>    drivers/gpu/drm/tiny/Kconfig | 1 +
>>>    drivers/video/fbdev/Kconfig  | 9 ++++-----
>>>    3 files changed, 7 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/arch/x86/boot/video-vesa.c b/arch/x86/boot/video-vesa.c
>>> index 7e185977a984..c2c6d35e3a43 100644
>>> --- a/arch/x86/boot/video-vesa.c
>>> +++ b/arch/x86/boot/video-vesa.c
>>> @@ -83,7 +83,7 @@ static int vesa_probe(void)
>>>    			   (vminfo.memory_layout == 4 ||
>>>    			    vminfo.memory_layout == 6) &&
>>>    			   vminfo.memory_planes == 1) {
>>> -#ifdef CONFIG_FB_BOOT_VESA_SUPPORT
>>> +#ifdef CONFIG_BOOT_VESA_SUPPORT
>>>    			/* Graphics mode, color, linear frame buffer
>>>    			   supported.  Only register the mode if
>>>    			   if framebuffer is configured, however,
>>> @@ -121,7 +121,7 @@ static int vesa_set_mode(struct mode_info *mode)
>>>    	if ((vminfo.mode_attr & 0x15) == 0x05) {
>>>    		/* It's a supported text mode */
>>>    		is_graphic = 0;
>>> -#ifdef CONFIG_FB_BOOT_VESA_SUPPORT
>>> +#ifdef CONFIG_BOOT_VESA_SUPPORT
>>>    	} else if ((vminfo.mode_attr & 0x99) == 0x99) {
>>>    		/* It's a graphics mode with linear frame buffer */
>>>    		is_graphic = 1;
>>> diff --git a/drivers/gpu/drm/tiny/Kconfig b/drivers/gpu/drm/tiny/Kconfig
>>> index 712e0004e96e..1bc30c64ed15 100644
>>> --- a/drivers/gpu/drm/tiny/Kconfig
>>> +++ b/drivers/gpu/drm/tiny/Kconfig
>>> @@ -54,6 +54,7 @@ config DRM_GM12U320
>>>    config DRM_SIMPLEDRM
>>>    	tristate "Simple framebuffer driver"
>>>    	depends on DRM && MMU
>>> +	select BOOT_VESA_SUPPORT if X86 && DRM_SIMPLEDRM = y
>>
>> We shouldn't select this option in drivers IMHO. Simple-framebuffer devices
>> with VESA are enabled with [1] and that should also select the
>> BOOT_VESA_SUPPORT.
> 
> Sounds ok to select from there, it should also cover simplefb then.
> 
> Thanks
> 
> Michal

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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