linux-kernel - Re: [PATCH] drm/msm/a6xx: Skip gpu secure fw load in EL2 mode

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Message-ID: <8fc505a0-91ad-4188-8627-fa28fc73a2ae@quicinc.com>
Date: Wed, 11 Dec 2024 06:10:06 +0530
From: Pavan Kondeti <quic_pkondeti@...cinc.com>
To: Connor Abbott <cwabbott0@...il.com>
CC: Akhil P Oommen <quic_akhilpo@...cinc.com>,
        Rob Clark
	<robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio
	<konradybcio@...nel.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        "Dmitry
 Baryshkov" <dmitry.baryshkov@...aro.org>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, "Simona
 Vetter" <simona@...ll.ch>,
        Elliot Berman <quic_eberman@...cinc.com>,
        "Pavan
 Kondeti" <quic_pkondeti@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] drm/msm/a6xx: Skip gpu secure fw load in EL2 mode

On Tue, Dec 10, 2024 at 05:52:27PM -0500, Connor Abbott wrote:
> On Mon, Dec 9, 2024 at 3:20 AM Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
> >
> > When kernel is booted in EL2, SECVID registers are accessible to the
> > KMD. So we can use that to switch GPU's secure mode to avoid dependency
> > on Zap firmware. Also, we can't load a secure firmware without a
> > hypervisor that supports it.
> >
> > Tested following configurations on sa8775p chipset (Adreno 663 gpu):
> >
> > 1. Gunyah (No KVM) - Loads zap shader based on DT
> > 2. KVM in VHE - Skips zap shader load and programs SECVID register
> > 3. KVM in nVHE - Loads zap shader based on DT
> > 4. Kernel in EL2 with CONFIG_KVM=n - Skips zap shader load and
> >         programs SECVID register
> >
> > For (1) and (3) configuration, this patch doesn't have any impact.
> > Driver loads secure firmware based on other existing hints.
> >
> > Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
> 
> For initializing CX_MISC_SW_FUSE_VALUE in a7xx_cx_mem_init(), we used
> !qcom_scm_is_available() to assume that the register is writable
> instead - can you just do that?
> 

qcom_scm_is_avaialble() returns true as most of the QC TZ firmware API
works w/ kernel running as bare metal i.e booted with EL2. Any services
that assume QC firmware @ EL2 (QHEE) is absent.

Thanks,
Pavan