[Intel-gfx] [RFC-v4 02/21] drm/i915/pxp: set KCR reg init during the boot time

[Huang, Sean Z]

Hi Wilson,

Thanks for bring up this. This is a necessary step during the booting to allow the ME communicate with display but we don't need turn off for unload actually.

Best regards,
Sean

-----Original Message-----
From: Chris Wilson <chris at chris-wilson.co.uk> 
Sent: Thursday, December 10, 2020 12:45 AM
To: Huang, Sean Z <sean.z.huang at intel.com>; Intel-gfx at lists.freedesktop.org
Subject: Re: [Intel-gfx] [RFC-v4 02/21] drm/i915/pxp: set KCR reg init during the boot time

Quoting Huang, Sean Z (2020-12-10 07:24:16)
> Set the KCR init during the boot time, which is required by hardware, 
> to allow us doing further protection operation such as sending 
> commands to GPU or TEE.
> 
> Signed-off-by: Huang, Sean Z <sean.z.huang at intel.com>
> ---
>  drivers/gpu/drm/i915/pxp/intel_pxp.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp.c 
> b/drivers/gpu/drm/i915/pxp/intel_pxp.c
> index ba43b2c923c7..c4815950567d 100644
> --- a/drivers/gpu/drm/i915/pxp/intel_pxp.c
> +++ b/drivers/gpu/drm/i915/pxp/intel_pxp.c
> @@ -6,6 +6,12 @@
>  #include "intel_pxp.h"
>  #include "intel_pxp_context.h"
>  
> +/* KCR register definitions */
> +#define KCR_INIT            _MMIO(0x320f0)
> +#define KCR_INIT_MASK_SHIFT (16)
> +/* Setting KCR Init bit is required after system boot */ #define 
> +KCR_INIT_ALLOW_DISPLAY_ME_WRITES (BIT(14) | (BIT(14) << 
> +KCR_INIT_MASK_SHIFT))
> +
>  int intel_pxp_init(struct intel_pxp *pxp)  {
>         struct intel_gt *gt = container_of(pxp, struct intel_gt, pxp); 
> @@ -16,6 +22,8 @@ int intel_pxp_init(struct intel_pxp *pxp)
>  
>         intel_pxp_ctx_init(&pxp->ctx);
>  
> +       intel_uncore_write(gt->uncore, KCR_INIT, 
> + KCR_INIT_ALLOW_DISPLAY_ME_WRITES);

So this looks dangerous to leave enabled after driver unload?
-Chris