linux-kernel - Re: [PATCH 02/11] drm/gma500: Use drm_aperture_remove_conflicting_pci

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Message-ID: <8a154783-b433-c9b8-bfe5-286dde1258e9@suse.de>
Date:   Thu, 12 Jan 2023 11:24:13 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     DRI Development <dri-devel@...ts.freedesktop.org>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [PATCH 02/11] drm/gma500: Use
 drm_aperture_remove_conflicting_pci_framebuffers

Hi

Am 12.01.23 um 10:59 schrieb Daniel Vetter:
> On Thu, Jan 12, 2023 at 10:04:48AM +0100, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 11.01.23 um 16:41 schrieb Daniel Vetter:
>>> This one nukes all framebuffers, which is a bit much. In reality
>>> gma500 is igpu and never shipped with anything discrete, so there should
>>> not be any difference.
>>>
>>> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
>>> ---
>>>    drivers/gpu/drm/gma500/psb_drv.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/gma500/psb_drv.c b/drivers/gpu/drm/gma500/psb_drv.c
>>> index cd9c73f5a64a..9b0daf90dc50 100644
>>> --- a/drivers/gpu/drm/gma500/psb_drv.c
>>> +++ b/drivers/gpu/drm/gma500/psb_drv.c
>>> @@ -429,7 +429,7 @@ static int psb_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>>>    	 * TODO: Refactor psb_driver_load() to map vdc_reg earlier. Then we
>>>    	 *       might be able to read the framebuffer range from the device.
>>>    	 */
>>> -	ret = drm_aperture_remove_framebuffers(true, &driver);
>>> +	ret = drm_aperture_remove_conflicting_pci_framebuffers(pdev, &driver);
>>
>> This does not work. The comment just above the changed line explains why.
>> The device uses shared memory similar to other integrated Intel chips. The
>> console is somewhere in a 16 MiB range, which has been stolen by the BIOS
>> from main memory. There's only a 1 MiB memory range on the device to program
>> the device. Unless you want to refactor as described, this call has to cover
>> the whole memory for now.
> 
> Uh. So it's maybe not so pretty, but what if I just call both functions?

That's ways more ugly IMHO.

> That way we get the vga handling through the pci one, and the "make sure
> there's no fb left" through the other one. Plus comment of course.
> 
> Otherwise we'd need to somehow keep the vga stuff in the non-pci paths,
> and that just feels all kinds of wrong to me.

With your patch applied, aperture_detach_devices() does all the work of 
removing. I'd add the following internal functions:

static void aperture_detach_head(bool is_primary)
{
	/*
	 * lengthy comment here
	 */
	if (is_primary)
		sysfb_disable()
}

static void aperture_detach_tail(bool remove_vga)
{
	if (remove_vga) {
		aperture_detach_devices(VGA_PHYS_)
		vga_remove_vgacon()
	}
}

And call both of them at the beginning/end of 
aperture_remove_conflicting_devices() and 
aperture_remove_conflicting_pci_devices().

You'd still need to primary argument to 
aperture_remove_conflicting_devices(), but there will be no code 
duplication with the aperture helpers and the purpose of each code 
fragment will be clearer.

Best regards
Thomas

> -Daniel

-- 
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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