linux-kernel - Re: [PATCH v2] drm/ast: Fix ARM compatibility

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Message-ID: <325512ba-b468-bca0-d3ef-a1c9cf464d62@aspeedtech.com>
Date:   Thu, 20 Apr 2023 17:37:01 +0800
From:   Jammy Huang <jammy_huang@...eedtech.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>, <airlied@...hat.com>
CC:     <airlied@...il.com>, <daniel@...ll.ch>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] drm/ast: Fix ARM compatibility

Hi Thomas,

Thanks for help. I will update a new patch per your comments

On 2023/4/20 下午 04:57, Thomas Zimmermann wrote:
> Hi
>
> Am 20.04.23 um 10:09 schrieb Jammy Huang:
>> ARM architecture only has 'memory', so all devices are accessed by
>> MMIO if possible.
>>
>> Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
>> ---
>>   v2 changes:
>>    - Use MMIO after AST2500 which enable MMIO by default.
>> ---
>>   drivers/gpu/drm/ast/ast_main.c | 9 +++++----
>>   1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ast/ast_main.c 
>> b/drivers/gpu/drm/ast/ast_main.c
>> index f83ce77127cb..d384e810fa4d 100644
>> --- a/drivers/gpu/drm/ast/ast_main.c
>> +++ b/drivers/gpu/drm/ast/ast_main.c
>> @@ -425,11 +425,12 @@ struct ast_private *ast_device_create(const 
>> struct drm_driver *drv,
>>           return ERR_PTR(-EIO);
>>         /*
>> -     * If we don't have IO space at all, use MMIO now and
>> -     * assume the chip has MMIO enabled by default (rev 0x20
>> -     * and higher).
>> +     * After AST2500, MMIO is enabled by default, and it should be 
>> adapted
>
> By 'adapted', you mean 'adopted'?
>
> Apart from that:
>
> Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
>
> I also ran this patch on an AST2100, which still works as before.
>
> Best regards
> Thomas
>
>> +     * to be compatible with Arm.
>>        */
>> -    if (!(pci_resource_flags(pdev, 2) & IORESOURCE_IO)) {
>> +    if (pdev->revision >= 0x40) {
>> +        ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
>> +    } else if (!(pci_resource_flags(pdev, 2) & IORESOURCE_IO)) {
>>           drm_info(dev, "platform has no IO space, trying MMIO\n");
>>           ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
>>       }
>>
>> base-commit: e62252bc55b6d4eddc6c2bdbf95a448180d6a08d
>
-- 
Best Regards
Jammy