linux-kernel - Re: [PATCH 05/19] iommu: add private interface for adreno-smmu

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Message-ID: <20200901035216.GM3715@yoga>
Date:   Mon, 31 Aug 2020 22:52:16 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Rob Clark <robdclark@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, iommu@...ts.linux-foundation.org,
        linux-arm-msm@...r.kernel.org,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Will Deacon <will@...nel.org>, freedreno@...ts.freedesktop.org,
        Sibi Sankar <sibis@...eaurora.org>,
        Vivek Gautam <vivek.gautam@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org,
        Rob Clark <robdclark@...omium.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 05/19] iommu: add private interface for adreno-smmu

On Thu 13 Aug 21:41 CDT 2020, Rob Clark wrote:

> From: Rob Clark <robdclark@...omium.org>
> 
> This interface will be used for drm/msm to coordinate with the
> qcom_adreno_smmu_impl to enable/disable TTBR0 translation.
> 
> Once TTBR0 translation is enabled, the GPU's CP (Command Processor)
> will directly switch TTBR0 pgtables (and do the necessary TLB inv)
> synchronized to the GPU's operation.  But help from the SMMU driver
> is needed to initially bootstrap TTBR0 translation, which cannot be
> done from the GPU.
> 
> Since this is a very special case, a private interface is used to
> avoid adding highly driver specific things to the public iommu
> interface.
> 
> Signed-off-by: Rob Clark <robdclark@...omium.org>

Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>

> ---
>  include/linux/adreno-smmu-priv.h | 36 ++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
>  create mode 100644 include/linux/adreno-smmu-priv.h
> 
> diff --git a/include/linux/adreno-smmu-priv.h b/include/linux/adreno-smmu-priv.h
> new file mode 100644
> index 000000000000..a889f28afb42
> --- /dev/null
> +++ b/include/linux/adreno-smmu-priv.h
> @@ -0,0 +1,36 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2020 Google, Inc
> + */
> +
> +#ifndef __ADRENO_SMMU_PRIV_H
> +#define __ADRENO_SMMU_PRIV_H
> +
> +#include <linux/io-pgtable.h>
> +
> +/**
> + * struct adreno_smmu_priv - private interface between adreno-smmu and GPU
> + *
> + * @cookie:        An opque token provided by adreno-smmu and passed
> + *                 back into the callbacks
> + * @get_ttbr1_cfg: Get the TTBR1 config for the GPUs context-bank
> + * @set_ttbr0_cfg: Set the TTBR0 config for the GPUs context bank.  A
> + *                 NULL config disables TTBR0 translation, otherwise
> + *                 TTBR0 translation is enabled with the specified cfg
> + *
> + * The GPU driver (drm/msm) and adreno-smmu work together for controlling
> + * the GPU's SMMU instance.  This is by necessity, as the GPU is directly
> + * updating the SMMU for context switches, while on the other hand we do
> + * not want to duplicate all of the initial setup logic from arm-smmu.
> + *
> + * This private interface is used for the two drivers to coordinate.  The
> + * cookie and callback functions are populated when the GPU driver attaches
> + * it's domain.
> + */
> +struct adreno_smmu_priv {
> +    const void *cookie;
> +    const struct io_pgtable_cfg *(*get_ttbr1_cfg)(const void *cookie);
> +    int (*set_ttbr0_cfg)(const void *cookie, const struct io_pgtable_cfg *cfg);
> +};
> +
> +#endif /* __ADRENO_SMMU_PRIV_H */
> \ No newline at end of file
> -- 
> 2.26.2
>