[PATCH] drm/ast: Fix ARM compatibility

[PATCH] drm/ast: Fix ARM compatibility

[Jammy Huang]

ARM architecture only has 'memory', so all devices are accessed by MMIO.

Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
---
 drivers/gpu/drm/ast/ast_main.c | 17 +----------------
 1 file changed, 1 insertion(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
index 794ffd4a29c5..f86d01e9f024 100644
--- a/drivers/gpu/drm/ast/ast_main.c
+++ b/drivers/gpu/drm/ast/ast_main.c
@@ -424,22 +424,7 @@ struct ast_device *ast_device_create(const struct drm_driver *drv,
 	if (!ast->regs)
 		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).
-	 */
-	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;
-	}
-
-	/* "map" IO regs if the above hasn't done so already */
-	if (!ast->ioregs) {
-		ast->ioregs = pcim_iomap(pdev, 2, 0);
-		if (!ast->ioregs)
-			return ERR_PTR(-EIO);
-	}
+	ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
 
 	ast_detect_chip(dev, &need_post);
 

base-commit: 254986e324add8a30d0019c6da59f81adc8b565f
-- 
2.25.1

Re: [PATCH] drm/ast: Fix ARM compatibility

[Jammy Huang]

Hi Thomas,

Could you help review this patch??

We met some problem on nvidia's ARM platfrom and need this patch to fix it.

On 2023/3/2 上午 10:19, Jammy Huang wrote:
> ARM architecture only has 'memory', so all devices are accessed by MMIO.
>
> Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
> ---
>   drivers/gpu/drm/ast/ast_main.c | 17 +----------------
>   1 file changed, 1 insertion(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/ast/ast_main.c b/drivers/gpu/drm/ast/ast_main.c
> index 794ffd4a29c5..f86d01e9f024 100644
> --- a/drivers/gpu/drm/ast/ast_main.c
> +++ b/drivers/gpu/drm/ast/ast_main.c
> @@ -424,22 +424,7 @@ struct ast_device *ast_device_create(const struct drm_driver *drv,
>   	if (!ast->regs)
>   		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).
> -	 */
> -	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;
> -	}
> -
> -	/* "map" IO regs if the above hasn't done so already */
> -	if (!ast->ioregs) {
> -		ast->ioregs = pcim_iomap(pdev, 2, 0);
> -		if (!ast->ioregs)
> -			return ERR_PTR(-EIO);
> -	}
> +	ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
>   
>   	ast_detect_chip(dev, &need_post);
>   
>
> base-commit: 254986e324add8a30d0019c6da59f81adc8b565f

-- 
Best Regards
Jammy

Re: [PATCH] drm/ast: Fix ARM compatibility

[Thomas Zimmermann]

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Hi

Am 07.04.23 um 04:09 schrieb Jammy Huang:
> Hi Thomas,
> 
> Could you help review this patch??
> 
> We met some problem on nvidia's ARM platfrom and need this patch to fix it.
> 
> On 2023/3/2 上午 10:19, Jammy Huang wrote:
>> ARM architecture only has 'memory', so all devices are accessed by MMIO.
>>
>> Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
>> ---
>>   drivers/gpu/drm/ast/ast_main.c | 17 +----------------
>>   1 file changed, 1 insertion(+), 16 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/ast/ast_main.c 
>> b/drivers/gpu/drm/ast/ast_main.c
>> index 794ffd4a29c5..f86d01e9f024 100644
>> --- a/drivers/gpu/drm/ast/ast_main.c
>> +++ b/drivers/gpu/drm/ast/ast_main.c
>> @@ -424,22 +424,7 @@ struct ast_device *ast_device_create(const struct 
>> drm_driver *drv,
>>       if (!ast->regs)
>>           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).
>> -     */
>> -    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;
>> -    }
>> -
>> -    /* "map" IO regs if the above hasn't done so already */
>> -    if (!ast->ioregs) {
>> -        ast->ioregs = pcim_iomap(pdev, 2, 0);

What happens on systems that use this branch?

Best regards
Thomas

>> -        if (!ast->ioregs)
>> -            return ERR_PTR(-EIO);
>> -    }
>> +    ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
>>       ast_detect_chip(dev, &need_post);
>>
>> base-commit: 254986e324add8a30d0019c6da59f81adc8b565f
> 

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

[Thomas Zimmermann]

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Hi

Am 18.04.23 um 03:23 schrieb Jammy Huang:
> 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 want to adapt MMIO only after this patch.

What I mean is that there's a comment that says "assume the chip has 
MMIO enabled by default (rev 0x20 and higher)". We also support revs 
before 0x20. What happens to them?

Best regards
Thomas

> 
> On 2023/4/17 下午 07:51, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 07.04.23 um 04:09 schrieb Jammy Huang:
>>> Hi Thomas,
>>>
>>> Could you help review this patch??
>>>
>>> We met some problem on nvidia's ARM platfrom and need this patch to 
>>> fix it.
>>>
>>> On 2023/3/2 上午 10:19, Jammy Huang wrote:
>>>> ARM architecture only has 'memory', so all devices are accessed by 
>>>> MMIO.
>>>>
>>>> Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
>>>> ---
>>>>   drivers/gpu/drm/ast/ast_main.c | 17 +----------------
>>>>   1 file changed, 1 insertion(+), 16 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/ast/ast_main.c 
>>>> b/drivers/gpu/drm/ast/ast_main.c
>>>> index 794ffd4a29c5..f86d01e9f024 100644
>>>> --- a/drivers/gpu/drm/ast/ast_main.c
>>>> +++ b/drivers/gpu/drm/ast/ast_main.c
>>>> @@ -424,22 +424,7 @@ struct ast_device *ast_device_create(const 
>>>> struct drm_driver *drv,
>>>>       if (!ast->regs)
>>>>           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).
>>>> -     */
>>>> -    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;
>>>> -    }
>>>> -
>>>> -    /* "map" IO regs if the above hasn't done so already */
>>>> -    if (!ast->ioregs) {
>>>> -        ast->ioregs = pcim_iomap(pdev, 2, 0);
>>
>> What happens on systems that use this branch?
>>
>> Best regards
>> Thomas
>>
>>>> -        if (!ast->ioregs)
>>>> -            return ERR_PTR(-EIO);
>>>> -    }
>>>> +    ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
>>>>       ast_detect_chip(dev, &need_post);
>>>>
>>>> base-commit: 254986e324add8a30d0019c6da59f81adc8b565f
>>>
>>
> -- 
> Best Regards
> Jammy
> 

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

[Jammy Huang]

Hi Thomas,

Thanks for you reminder. The comment you mentioned is added in 2014 for 
AST2400 rev 0x20, which means MMIO is not enable by default before that 
revision. I will send another patch to handle it.


On 2023/4/18 下午 03:24, Thomas Zimmermann wrote:
> Hi
>
> Am 18.04.23 um 03:23 schrieb Jammy Huang:
>> 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 want to adapt MMIO only after this patch.
>
> What I mean is that there's a comment that says "assume the chip has 
> MMIO enabled by default (rev 0x20 and higher)". We also support revs 
> before 0x20. What happens to them?
>
> Best regards
> Thomas
>
>>
>> On 2023/4/17 下午 07:51, Thomas Zimmermann wrote:
>>> Hi
>>>
>>> Am 07.04.23 um 04:09 schrieb Jammy Huang:
>>>> Hi Thomas,
>>>>
>>>> Could you help review this patch??
>>>>
>>>> We met some problem on nvidia's ARM platfrom and need this patch to 
>>>> fix it.
>>>>
>>>> On 2023/3/2 上午 10:19, Jammy Huang wrote:
>>>>> ARM architecture only has 'memory', so all devices are accessed by 
>>>>> MMIO.
>>>>>
>>>>> Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com>
>>>>> ---
>>>>>   drivers/gpu/drm/ast/ast_main.c | 17 +----------------
>>>>>   1 file changed, 1 insertion(+), 16 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/ast/ast_main.c 
>>>>> b/drivers/gpu/drm/ast/ast_main.c
>>>>> index 794ffd4a29c5..f86d01e9f024 100644
>>>>> --- a/drivers/gpu/drm/ast/ast_main.c
>>>>> +++ b/drivers/gpu/drm/ast/ast_main.c
>>>>> @@ -424,22 +424,7 @@ struct ast_device *ast_device_create(const 
>>>>> struct drm_driver *drv,
>>>>>       if (!ast->regs)
>>>>>           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).
>>>>> -     */
>>>>> -    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;
>>>>> -    }
>>>>> -
>>>>> -    /* "map" IO regs if the above hasn't done so already */
>>>>> -    if (!ast->ioregs) {
>>>>> -        ast->ioregs = pcim_iomap(pdev, 2, 0);
>>>
>>> What happens on systems that use this branch?
>>>
>>> Best regards
>>> Thomas
>>>
>>>>> -        if (!ast->ioregs)
>>>>> -            return ERR_PTR(-EIO);
>>>>> -    }
>>>>> +    ast->ioregs = ast->regs + AST_IO_MM_OFFSET;
>>>>>       ast_detect_chip(dev, &need_post);
>>>>>
>>>>> base-commit: 254986e324add8a30d0019c6da59f81adc8b565f
>>>>
>>>
>> -- 
>> Best Regards
>> Jammy
>>
>
-- 
Best Regards
Jammy