linux-kernel - Re: [PATCH 01/11] drm/ast: Use drm_aperture_remove_conflicting_pci

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Date:   Tue, 18 Apr 2023 08:53:48 +0800
From:   Jammy Huang <jammy_huang@...eedtech.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>
CC:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Dave Airlie <airlied@...hat.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Helge Deller <deller@....de>, <linux-fbdev@...r.kernel.org>
Subject: Re: [PATCH 01/11] drm/ast: Use
 drm_aperture_remove_conflicting_pci_framebuffers

Hi Thomas,

The Intel(x86) CPUs have a separate address space for "IO", but the ARM 
architecture only has "memory", so all IO devices are accessed as if 
they were memory. Which means ARM does not support isolated IO. Here is 
a related discussion on ARM's forum.

https://community.arm.com/support-forums/f/architectures-and-processors-forum/52046/how-to-read-write-an-i-o-port-in-aarch64

Thus, we adapt MMIO only after this patch.


On 2023/4/4 下午 10:45, Thomas Zimmermann wrote:
> Hi,
>
> FYI I have merged patches 1, 6 and 7 of this patchset. They look fine 
> and are worthwhile fixes on their own.
>
> Best regards
> Thomas
>
> Am 11.01.23 um 16:41 schrieb Daniel Vetter:
>> It's just open coded and matches.
>>
>> Note that Thomas said that his version apparently failed for some
>> reason, but hey maybe we should try again.
>>
>> Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
>> Cc: Dave Airlie <airlied@...hat.com>
>> Cc: Thomas Zimmermann <tzimmermann@...e.de>
>> Cc: Javier Martinez Canillas <javierm@...hat.com>
>> Cc: Helge Deller <deller@....de>
>> Cc: linux-fbdev@...r.kernel.org
>> ---
>>   drivers/gpu/drm/ast/ast_drv.c | 16 +---------------
>>   1 file changed, 1 insertion(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ast/ast_drv.c 
>> b/drivers/gpu/drm/ast/ast_drv.c
>> index 420fc75c240e..3ac24a780f50 100644
>> --- a/drivers/gpu/drm/ast/ast_drv.c
>> +++ b/drivers/gpu/drm/ast/ast_drv.c
>> @@ -90,27 +90,13 @@ static const struct pci_device_id ast_pciidlist[] 
>> = {
>>     MODULE_DEVICE_TABLE(pci, ast_pciidlist);
>>   -static int ast_remove_conflicting_framebuffers(struct pci_dev *pdev)
>> -{
>> -    bool primary = false;
>> -    resource_size_t base, size;
>> -
>> -    base = pci_resource_start(pdev, 0);
>> -    size = pci_resource_len(pdev, 0);
>> -#ifdef CONFIG_X86
>> -    primary = pdev->resource[PCI_ROM_RESOURCE].flags & 
>> IORESOURCE_ROM_SHADOW;
>> -#endif
>> -
>> -    return drm_aperture_remove_conflicting_framebuffers(base, size, 
>> primary, &ast_driver);
>> -}
>> -
>>   static int ast_pci_probe(struct pci_dev *pdev, const struct 
>> pci_device_id *ent)
>>   {
>>       struct ast_private *ast;
>>       struct drm_device *dev;
>>       int ret;
>>   -    ret = ast_remove_conflicting_framebuffers(pdev);
>> +    ret = drm_aperture_remove_conflicting_pci_framebuffers(pdev, 
>> &ast_driver);
>>       if (ret)
>>           return ret;
>
-- 
Best Regards
Jammy