linux-kernel - Re: [PATCH v2 15/22] wifi: ath12k: add BDF address in hardware parameter

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Message-ID: <b3581663-8dc0-44d4-9395-df385316bb09@quicinc.com>
Date: Mon, 9 Dec 2024 09:53:05 +0530
From: Raj Kumar Bhagat <quic_rajkbhag@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        <ath12k@...ts.infradead.org>
CC: <linux-wireless@...r.kernel.org>, Kalle Valo <kvalo@...nel.org>,
        "Rob
 Herring" <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        "Conor
 Dooley" <conor+dt@...nel.org>,
        Jeff Johnson <jjohnson@...nel.org>,
        "Bjorn
 Andersson" <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v2 15/22] wifi: ath12k: add BDF address in hardware
 parameter

On 12/6/2024 4:19 PM, Konrad Dybcio wrote:
> On 6.12.2024 5:34 AM, Raj Kumar Bhagat wrote:
>> On 12/5/2024 11:12 PM, Konrad Dybcio wrote:
>>> On 3.12.2024 10:18 AM, Raj Kumar Bhagat wrote:
>>>> On 11/4/2024 7:46 PM, Konrad Dybcio wrote:
>>>>> On 15.10.2024 8:26 PM, Raj Kumar Bhagat wrote:
>>>>>> The Ath2k AHB device (IPQ5332) firmware requests BDF_MEM_REGION_TYPE
>>>>>> memory during QMI memory requests. This memory is part of the
>>>>>> HOST_DDR_REGION_TYPE. Therefore, add the BDF memory address to the
>>>>>> hardware parameter and provide this memory address to the firmware
>>>>>> during QMI memory requests.
>>>>>
>>>>> Sounds like something to put in the device tree, no?
>>>>>
>>>>
>>>> This BDF memory address is the RAM offset. We did add this in device tree in
>>>> version 1. This is removed from device tree in v2 based on the review comment that
>>>> DT should not store RAM offset.
>>>>
>>>> refer below link:
>>>> Link: https://lore.kernel.org/all/f8cd9c3d-47e1-4709-9334-78e4790acef0@kernel.org/
>>>
>>> Right, I think this could be something under /reserved-memory instead
>>>
>>
>> Thanks for the suggestion. However, the BDF_MEM_REGION_TYPE is already within the
>> memory reserved for HOST_DDR_REGION_TYPE through /reserved-memory. Therefore, reserving
>> the memory for BDF_MEM_REGION_TYPE again in the Device Tree (DT) will cause a warning
>> for 'overlapping memory reservation'.
> 
> Then you can grab a handle to it with of_reserved_mem_lookup()
> and of_reserved_mem_device_init_by_idx()
> 

The memory HOST_DDR_REGION_TYPE is a bigger memory around 43MB, while the memory
BDF_MEM_REGION_TYPE is smaller around 256KB within HOST_DDR_REGION_TYPE, Using the
above mentioned API we still have to store the offset in ath12k to point at memory
BDF_MEM_REGION_TYPE from the start of HOST_DDR_REGION_TYPE.