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

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Message-ID: <96416911-bca3-b007-b036-1c4463e83aaa@quicinc.com>
Date:   Tue, 11 Apr 2023 15:32:05 -0700
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Marijn Suijten <marijn.suijten@...ainline.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>
CC:     <freedreno@...ts.freedesktop.org>, <quic_sbillaka@...cinc.com>,
        <airlied@...il.com>, <andersson@...nel.org>, <robdclark@...il.com>,
        <dri-devel@...ts.freedesktop.org>, <dianders@...omium.org>,
        <vkoul@...nel.org>, <agross@...nel.org>, <daniel@...ll.ch>,
        <linux-arm-msm@...r.kernel.org>, <dmitry.baryshkov@...aro.org>,
        <swboyd@...omium.org>, <sean@...rly.run>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [Freedreno] [PATCH] drm/msm/dpu: add DSC range checking during
 resource reservation

Hi Marijn

On 4/11/2023 3:24 PM, Marijn Suijten wrote:
> 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.
> 

The purpose of this check is that today all our blocks in RM use the 
DSC_* enum as the size.

struct dpu_hw_blk *dsc_blks[DSC_MAX - DSC_0];

If the device tree ends up with more DSC blocks than the DSC_* enum, how 
can we avoid this issue today? Not because its a bug in device tree but 
how many static number of DSCs are hard-coded in RM.

And like you said, this is not specific to DSC. Such checks are present 
for other blocks too.

>> 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
>>