[PATCH] drm/vmwgfx: Stop requesting the pci regions

[Javier Martinez Canillas]

On 1/19/22 16:50, Thomas Zimmermann wrote:

[snip]

>>>> IMHO the best solution is to drop IORESOURCE_BUSY from sysfb and have
>>>> drivers register/release the range with _BUSY. That would signal the
>>>> memory belongs to the sysfb device but is not busy unless a driver
>>>> has
>>>> been bound. After simplefb released the range, it should be 'non-
>>>> busy'
>>>> again and available for vmwgfx. Simpledrm does a hot-unplug of the
>>>> sysfb
>>>> device, so the memory range gets released entirely. If you want, I'll
>>>> prepare some patches for this scenario.
>>>
>>> Attached is a patch that implements this. Doing
>>>
>>>    cat /proc/iomem
>>>     ...
>>>     e0000000-efffffff : 0000:00:02.0
>>>
>>>       e0000000-e07e8fff : BOOTFB
>>>
>>>         e0000000-e07e8fff : simplefb
>>>
>>>     ...
>>>
>>> shows the memory. 'BOOTFB' is the simple-framebuffer device and
>>> 'simplefb' is the driver. Only the latter uses _BUSY. Same for
>>> and the memory canbe acquired by vmwgfx.
>>>
>>> Zack, please test this patch. If it works, I'll send out the real
>>> patchset.
>>
>> Hmm, the patch looks good but it doesn't work. After boot: /proc/iomem
>> 50000000-7fffffff : pcie at 0x40000000
>>    78000000-7fffffff : 0000:00:0f.0
>>      78000000-782fffff : BOOTFB
>>
>> and vmwgfx fails on pci_request_regions:
>>
>> kernel: fb0: switching to vmwgfx from simple
>> kernel: Console: switching to colour dummy device 80x25
>> kernel: vmwgfx 0000:00:0f.0: BAR 2: can't reserve [mem 0x78000000-
>> 0x7fffffff 64bit pref]
>> kernel: vmwgfx: probe of 0000:00:0f.0 failed with error -16
>>
>> leaving the system without a fb driver.
> 
> OK, I suspect that it would work if you use simpledrm instead of 
> simplefb. Could you try please? You'd have to build DRM and simpledrm 
> into the kernel binary.
>

Yes, I believe that should work.
 Zack, could you please try if just the following [0] make it works ?

That is, dropping the IORESOURCE_BUSY but not doing the memory region
request / release in simplefb and keeping it in the vmwgfx driver.

[0]:
>From da6de1430b9dc252eccf2d6fee0446d33375fa6d Mon Sep 17 00:00:00 2001
From: Javier Martinez Canillas <javierm at redhat.com>
Date: Wed, 19 Jan 2022 14:41:25 +0100
Subject: [PATCH] drivers/firmware: Don't mark as busy the simple-framebuffer
 IO resource

The sysfb_create_simplefb() function requests a IO memory resource for the
simple-framebuffer platform device, but it also marks it as busy which led
to drivers requesting the same memory resource to fail.

Let's drop the IORESOURCE_BUSY flag and let drivers to request it as busy
instead.

Signed-off-by: Javier Martinez Canillas <javierm at redhat.com>
---
 drivers/firmware/sysfb_simplefb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/sysfb_simplefb.c b/drivers/firmware/sysfb_simplefb.c
index 303a491e520d..76c4abc42a30 100644
--- a/drivers/firmware/sysfb_simplefb.c
+++ b/drivers/firmware/sysfb_simplefb.c
@@ -99,7 +99,7 @@ __init int sysfb_create_simplefb(const struct screen_info *si,
 
 	/* setup IORESOURCE_MEM as framebuffer memory */
 	memset(&res, 0, sizeof(res));
-	res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+	res.flags = IORESOURCE_MEM;
 	res.name = simplefb_resname;
 	res.start = base;
 	res.end = res.start + length - 1;
-- 
2.33.1