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

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Message-ID: <1657dccb-3d03-420a-9ffa-5601ae212fd9@bosc.ac.cn>
Date: Tue, 25 Nov 2025 17:55:34 +0800
From: ZhangZhiJie <zhangzhijie@...c.ac.cn>
To: Jani Nikula <jani.nikula@...ux.intel.com>, 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 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.

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)
>