linux-kernel - Re: [PATCH v2] mhi: host: Add standard ELF header image download functionality

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Message-ID: <87edjvwb0a.fsf@kernel.org>
Date:   Tue, 22 Aug 2023 14:51:33 +0300
From:   Kalle Valo <kvalo@...nel.org>
To:     Qiang Yu <quic_qianyu@...cinc.com>
Cc:     mani@...nel.org, quic_jhugo@...cinc.com, mhi@...ts.linux.dev,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        quic_cang@...cinc.com, quic_mrana@...cinc.com
Subject: Re: [PATCH v2] mhi: host: Add standard ELF header image download
 functionality

Qiang Yu <quic_qianyu@...cinc.com> writes:

> From: Mayank Rana <quic_mrana@...cinc.com>
>
> Some devices (e.g. WLAN chips) are unable to handle the non-standard ELF
> format of the FBC image and thus need special handling of the FBC image.
>
> Add standard_elf_image flag which makes decision in terms of how FBC image
> based AMSS image is being downloaded with connected endpoint.
> FBC image is having two image combine: SBL image + AMSS image.
> 1. FBC image download using legacy single ELF header image format:
> - SBL image: 512KB of FBC image is downloaded using BHI.
> - AMSS image: full FBC image is downloaded using BHIe.
> 2. FBC image download using separate ELF header image format:
> - SBL image: 512 KB of FBC image is downloaded using BHI.
> - AMSS image: 512 KB onward FBC image is downloaded using BHIe.
> There is no change for SBL image download. Although AMSS image start
> address is end address of SBL image while using separate ELF header format.
>
> Signed-off-by: Mayank Rana <quic_mrana@...cinc.com>
> [quic_qianyu@...cinc.com: Update commit message, minor updates]
> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>

I guess this is for an out-of-tree driver? I haven't heard any such
requirements for ath11k or ath12k.

> --- a/drivers/bus/mhi/host/boot.c
> +++ b/drivers/bus/mhi/host/boot.c
> @@ -495,6 +495,13 @@ void mhi_fw_load_handler(struct mhi_controller *mhi_cntrl)
>  	 * device transitioning into MHI READY state
>  	 */
>  	if (mhi_cntrl->fbc_download) {
> +		dev_dbg(dev, "standard_elf_image: %s\n",
> +				(mhi_cntrl->standard_elf_image ? "True" : "False"));
> +		if (mhi_cntrl->standard_elf_image) {
> +			fw_data = firmware->data + mhi_cntrl->sbl_size;
> +			fw_sz = fw_sz - mhi_cntrl->sbl_size;
> +		}

So you are basically skipping the first sbl_size bytes of the firmware
file? Why not just fix the firmware file in userspace? Or maybe you can
use the recently added[1] mhi_cntrl->fw_data pointer and handle this in
your driver instead?

[1] https://git.kernel.org/pub/scm/linux/kernel/git/mani/mhi.git/commit/?h=mhi-next&id=efe47a18e43f59f063a82ccaa464a3b4844bb8a8

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