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

[ZhangZhiJie]

On 2025/11/25 18:13, Jani Nikula wrote:
On Tue, 25 Nov 2025, ZhangZhiJie <zhangzhi...@bosc.ac.cn> wrote:
On 2025/11/24 20:24, Jani Nikula wrote:
On Mon, 24 Nov 2025, zhangzhijie <zhangzhi...@bosc.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.

Yes, i compiled Xe driver, and it's occured load access fault when not 
disable  VGA_SEQ_*.

can found this link 
https://github.com/geerlingguy/raspberry-pi-pcie-devices/issues/510#issuecomment-3383284831

Thanks.
BR.
ZhiJie



Thanks.
BR.
ZhiJie

Signed-off-by: zhangzhijie <zhangzhi...@bosc.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)