linux-kernel - Re: [PATCH 1/4] soc: qcom: aoss: Move length requirements from caller

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Message-ID: <71460c5f-2aac-67b0-3779-d748f9e512aa@quicinc.com>
Date:   Mon, 31 Jul 2023 16:46:48 -0700
From:   Chris Lew <quic_clew@...cinc.com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
CC:     Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Alex Elder <elder@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-remoteproc@...r.kernel.org>
Subject: Re: [PATCH 1/4] soc: qcom: aoss: Move length requirements from caller



On 7/31/2023 4:10 PM, Bjorn Andersson wrote:
> On Mon, Jul 31, 2023 at 02:29:44PM -0700, Chris Lew wrote:
>>
>>
>> On 7/30/2023 9:10 PM, Bjorn Andersson wrote:
>>> diff --git a/drivers/soc/qcom/qcom_aoss.c b/drivers/soc/qcom/qcom_aoss.c
>>>    	/* The message RAM only implements 32-bit accesses */
>>>    	__iowrite32_copy(qmp->msgram + qmp->offset + sizeof(u32),
>>> -			 data, len / sizeof(u32));
>>> -	writel(len, qmp->msgram + qmp->offset);
>>> +			 buf, sizeof(buf) / sizeof(u32));
>>> +	writel(sizeof(buf), qmp->msgram + qmp->offset);
>>
>> Looks like we are telling the firmware the packet size will always be
>> QMP_MSG_LEN?
>>
>> This should be ok but might be a problem when debugging. The AOSS firmware
>> only logs size of the message instead of the full string because of memory
>> constraints.
>>
> 
> Until now ipa_power_retention() has been passing 36 here, everyone else
> 64, so it is ok.
> 
>> We would normally match the firmware and host logs based on size, but won't
>> be able to differentiate this way with a fixed size.
> 
> I don't mind us changing it to ALIGN(len, 4), but as that would change
> the current behavior I'd like to do so in a subsequent patch.
> 
> Speaking of behavior, is 64 the max message size? We inherited the 64
> from the initial downstream implementation, but qmp->size is quite a bit
> bigger.
> 

The max message size the firmware can handle is 0x64, so 100 bytes, but 
I haven't seen any messages go above 64 bytes.

> Regards,
> Bjorn