linux-kernel - Re: [PATCH] drm/msm/dpu: add DSC range checking during resource reservation

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Date:   Wed, 12 Apr 2023 00:24:06 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>
Cc:     robdclark@...il.com, sean@...rly.run, swboyd@...omium.org,
        dianders@...omium.org, vkoul@...nel.org, daniel@...ll.ch,
        airlied@...il.com, agross@...nel.org, dmitry.baryshkov@...aro.org,
        andersson@...nel.org, quic_abhinavk@...cinc.com,
        quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dpu: add DSC range checking during resource
 reservation

Again, don't forget to include previous reviewers in cc, please :)

On 2023-04-11 14:09:40, Kuogee Hsieh wrote:
> Perform DSC range checking to make sure correct DSC is requested before
> reserve resource for it.

This isn't performing any range checking for resource reservations /
requests: this is only validating the constants written in our catalog
and seems rather useless.  It isn't fixing any real bug either, so the
Fixes: tag below seems extraneous.

Given prior comments from Abhinav that "the kernel should be trusted",
we should remove this validation for all the other blocks instead.

> Fixes: c985d7bb64ff ("drm/msm/disp/dpu1: Add DSC support in RM")
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> index f4dda88..95e58f1 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c
> @@ -1,6 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  /*
>   * Copyright (c) 2016-2018, The Linux Foundation. All rights reserved.
> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved.
>   */
>  
>  #define pr_fmt(fmt)	"[drm:%s] " fmt, __func__
> @@ -250,6 +251,11 @@ int dpu_rm_init(struct dpu_rm *rm,
>  		struct dpu_hw_dsc *hw;
>  		const struct dpu_dsc_cfg *dsc = &cat->dsc[i];
>  
> +		if (dsc->id < DSC_0 || dsc->id >= DSC_MAX) {
> +			DPU_ERROR("skip dsc %d with invalid id\n", dsc->id);
> +			continue;
> +		}
> +
>  		hw = dpu_hw_dsc_init(dsc->id, mmio, cat);
>  		if (IS_ERR_OR_NULL(hw)) {
>  			rc = PTR_ERR(hw);
> @@ -557,8 +563,10 @@ static int _dpu_rm_make_reservation(
>  	}
>  
>  	ret  = _dpu_rm_reserve_dsc(rm, global_state, enc, &reqs->topology);
> -	if (ret)
> +	if (ret) {
> +		DPU_ERROR("unable to find appropriate DSC\n");

This, while a nice addition, should go in a different patch.

Thanks!

- Marijn

>  		return ret;
> +	}
>  
>  	return ret;
>  }
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>