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From: Kalle Valo <kvalo@kernel.org>
To: Marc Gonzalez <mgonzalez@freebox.fr>
Cc: Jeff Johnson <quic_jjohnson@quicinc.com>,  ath10k
 <ath10k@lists.infradead.org>,  wireless <linux-wireless@vger.kernel.org>,
  DT <devicetree@vger.kernel.org>,  Rob Herring <robh+dt@kernel.org>,
  Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,  Conor Dooley
 <conor+dt@kernel.org>,  Pierre-Hugues Husson <phhusson@freebox.fr>,  Jami
 Kettunen <jamipkettunen@gmail.com>,  Jeffrey Hugo <quic_jhugo@quicinc.com>
Subject: Re: [PATCH 1/2] dt-bindings: net: wireless: ath10k: add
 qcom,no-msa-ready-indicator prop
References: <14daa98e-7fd3-4ebb-87bb-5d2c1fba679f@freebox.fr>
	<b8de96c7-cbb6-4a09-a4d4-2c11b3ab3e01@freebox.fr>
	<871q8wk7o3.fsf@kernel.org>
	<3392f356-7b19-483d-b9f8-3bd84068fa52@freebox.fr>
	<87wmqoilzf.fsf@kernel.org>
	<c58e67e6-6a7f-4963-86b9-580165bf05ba@freebox.fr>
Date: Fri, 01 Mar 2024 10:10:29 +0200
In-Reply-To: <c58e67e6-6a7f-4963-86b9-580165bf05ba@freebox.fr> (Marc
	Gonzalez's message of "Wed, 28 Feb 2024 18:19:03 +0100")
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Marc Gonzalez <mgonzalez@freebox.fr> writes:

>> Here's one example where in ath10k we use a feature bit as a workaround:
>> 
>> 	/* Don't trust error code from otp.bin */
>> 	ATH10K_FW_FEATURE_IGNORE_OTP_RESULT = 7,
>> 
>>         ....
>> 
>> 	if (!(skip_otp || test_bit(ATH10K_FW_FEATURE_IGNORE_OTP_RESULT,
>> 				   ar->running_fw->fw_file.fw_features)) &&
>> 	    result != 0) {
>> 		ath10k_err(ar, "otp calibration failed: %d", result);
>> 		return -EINVAL;
>> 	}
>> 
>> BTW for modifying firmware-N.bin files we have a script here:
>> 
>> https://github.com/qca/qca-swiss-army-knife/blob/master/tools/scripts/ath10k/ath10k-fwencoder
>
> If I understand correctly, you are saying that there is
> (maybe... probably) a bug in the FW, so it makes sense to
> tag that specific FW file with a special bit which the kernel
> will interpret as "this FW is broken in a specific way;
> and here's how to work around the issue."
>
> So this bit would serve the same purpose as my proposed
> "qcom,no-msa-ready-indicator" bit (that bit existed instead
> in my board's device tree).
>
> The problem I see is that the firmware files are signed.
> Thus, changing a single bit breaks the verification...
> UNLESS the FW format allows for a signed section ALONG-SIDE
> an unsigned section?

firmware-N.bin is ath10k specific container file format and we (the
Linux community) have full access to it using ath10k-fwencoder, there's
no signing or anything like that. One of the major reasons why it was
designed was to handle differences between firmware branches, just like
in this case.

Of course plan A should be to fix the firmware but if that doesn't work
out then plan B could be using the feature bit in firmware-N.bin.

BTW related to this Dmitry is extending firmware-N.bin handling for
WCN3990, you will most likely need to use that:

https://patchwork.kernel.org/project/linux-wireless/cover/20240130-wcn3990-firmware-path-v1-0-826b93202964@linaro.org/

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