linux-kernel - Re: [PATCH v2] i915: Support Intel GPU porting on any non-x86 system.

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Message-ID: <58728a8ae8f0a3e92be203a9296d120fd12da8d5@intel.com>
Date: Tue, 25 Nov 2025 12:13:25 +0200
From: Jani Nikula <jani.nikula@...ux.intel.com>
To: ZhangZhiJie <zhangzhijie@...c.ac.cn>, jeff@...fgeerling.com,
 wangran@...c.ac.cn, zhangjian@...c.ac.cn, daniel@...ll.ch,
 rodrigo.vivi@...el.com, joonas.lahtinen@...ux.intel.com,
 tursulin@...ulin.net, airlied@...il.com, intel-gfx@...ts.freedesktop.org,
 intel-xe@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, guoyaxing@...c.ac.cn
Subject: Re: [PATCH v2] i915: Support Intel GPU porting on any non-x86 system.

On Tue, 25 Nov 2025, ZhangZhiJie <zhangzhijie@...c.ac.cn> wrote:
> On 2025/11/24 20:24, Jani Nikula wrote:
>> On Mon, 24 Nov 2025, zhangzhijie <zhangzhijie@...c.ac.cn> wrote:
>>> inb/outb speccial wire not support on other ARCH.
>>> Should detect whether arch platform support or not.
>> 
>> Seems to me it inb/outb depend on CONFIG_HAS_IOPORT. Which arch are you
>> talking about specifically?
>
> riscv , has CONFIG_HAS_IOPORT.  is using for serial, GPIO., etc.

What is the actual failure mode you see?

Does it build?

BR,
Jani.



>
> Thanks.
> BR.
> ZhiJie
>> 
>>> Signed-off-by: zhangzhijie <zhangzhijie@...c.ac.cn>
>>> ---
>>>   drivers/gpu/drm/i915/display/intel_vga.c | 27 ++++++++++++++++++------
>>>   1 file changed, 20 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/display/intel_vga.c b/drivers/gpu/drm/i915/display/intel_vga.c
>>> index 6e125564db34..d5d6c4ba6434 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_vga.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_vga.c
>>> @@ -41,6 +41,15 @@ static bool has_vga_pipe_sel(struct intel_display *display)
>>>   	return DISPLAY_VER(display) < 7;
>>>   }
>>>   
>>> +static bool intel_arch_support_vga_pm(struct intel_display *display)
>>> +{
>>> +#if defined(CONFIG_X86) || defined(CONFIG_X86_64)
>>> +	return true;
>>> +#else
>>> +	return false;
>>> +#endif
>>> +}
>>> +
>>>   /* Disable the VGA plane that we never use */
>>>   void intel_vga_disable(struct intel_display *display)
>>>   {
>>> @@ -66,11 +75,13 @@ void intel_vga_disable(struct intel_display *display)
>>>   
>>>   	/* WaEnableVGAAccessThroughIOPort:ctg,elk,ilk,snb,ivb,vlv,hsw */
>>>   	vga_get_uninterruptible(pdev, VGA_RSRC_LEGACY_IO);
>>> -	outb(0x01, VGA_SEQ_I);
>>> -	sr1 = inb(VGA_SEQ_D);
>>> -	outb(sr1 | VGA_SR01_SCREEN_OFF, VGA_SEQ_D);
>>> -	vga_put(pdev, VGA_RSRC_LEGACY_IO);
>>> -	udelay(300);
>>> +	if (likely(intel_arch_support_vga_pm(display))) {
>> 
>> As a rule of thumb, please do not use likely/unlikely, at all.
>> 
>> Here, intel_arch_support_vga_pm() is evaluated at build time, and the
>> likely has no functional value, only dubious documentation value.
>> 
>>> +		outb(0x01, VGA_SEQ_I);
>>> +		sr1 = inb(VGA_SEQ_D);
>>> +		outb(sr1 | VGA_SR01_SCREEN_OFF, VGA_SEQ_D);
>>> +		vga_put(pdev, VGA_RSRC_LEGACY_IO);
>> 
>> Both or neither get/put need to be inside the branch. Now you only get,
>> never put, on non-x86.
>> 
>> BR,
>> Jani.
>> 
>>> +		udelay(300);
>>> +	}
>>>   
>>>   	intel_de_write(display, vga_reg, VGA_DISP_DISABLE);
>>>   	intel_de_posting_read(display, vga_reg);
>>> @@ -91,8 +102,10 @@ void intel_vga_reset_io_mem(struct intel_display *display)
>>>   	 * and error messages.
>>>   	 */
>>>   	vga_get_uninterruptible(pdev, VGA_RSRC_LEGACY_IO);
>>> -	outb(inb(VGA_MIS_R), VGA_MIS_W);
>>> -	vga_put(pdev, VGA_RSRC_LEGACY_IO);
>>> +	if (likely(intel_arch_support_vga_pm(display))) {
>>> +		outb(inb(VGA_MIS_R), VGA_MIS_W);
>>> +		vga_put(pdev, VGA_RSRC_LEGACY_IO);
>>> +	}
>>>   }
>>>   
>>>   int intel_vga_register(struct intel_display *display)
>> 
>

-- 
Jani Nikula, Intel