linux-kernel - Re: [PATCH] remoteproc: qcom_q6v5: Assign mpss region to Q6 before MBA cold boot

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Date:   Tue, 15 Sep 2020 18:33:47 +0000
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Sibi Sankar <sibis@...eaurora.org>
Cc:     agross@...nel.org, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        ohad@...ery.com, evgreen@...omium.org, swboyd@...omium.org
Subject: Re: [PATCH] remoteproc: qcom_q6v5: Assign mpss region to Q6 before
 MBA cold boot

On Tue 15 Sep 17:37 UTC 2020, Sibi Sankar wrote:

> On secure devices which support warm reset, the modem subsystem requires
> access to the mpss region to clear them out. Hence assign the mpss region
> to Q6 before MBA cold boot. This will be a nop during a modem SSR.
> 
> Signed-off-by: Sibi Sankar <sibis@...eaurora.org>
> ---
> 
> I didn't want to add any new flags for warm reset support because
> calling xfer for mpss to q6 shouldn't have any side effects on
> platforms that don't support warm resets.
> 

As discussed offline, I don't see a problem with unconditionally handing
over the ownership of the region during this time frame. So let's just
generalize the comment below a little bit and I'm happy with this
change.

Thanks,
Bjorn

>  drivers/remoteproc/qcom_q6v5_mss.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/remoteproc/qcom_q6v5_mss.c b/drivers/remoteproc/qcom_q6v5_mss.c
> index c401bcc263fa5..cc5b7edc02c73 100644
> --- a/drivers/remoteproc/qcom_q6v5_mss.c
> +++ b/drivers/remoteproc/qcom_q6v5_mss.c
> @@ -931,6 +931,18 @@ static int q6v5_mba_load(struct q6v5 *qproc)
>  		goto assert_reset;
>  	}
>  
> +	/**
> +	 * On secure devices which support warm reboot, the modem subsystem's cold boot is similar
> +	 * to an SSR sequence i.e the mba requires access to the modem memory to clear it out during
> +	 * Q6 cold boot. For modem SSR it will be a nop.
> +	 */
> +	ret = q6v5_xfer_mem_ownership(qproc, &qproc->mpss_perm, false, true,
> +				      qproc->mpss_phys, qproc->mpss_size);
> +	if (ret) {
> +		dev_err(qproc->dev, "assigning Q6 access to mpss memory failed: %d\n", ret);
> +		goto disable_active_clks;
> +	}
> +
>  	/* Assign MBA image access in DDR to q6 */
>  	ret = q6v5_xfer_mem_ownership(qproc, &qproc->mba_perm, false, true,
>  				      qproc->mba_phys, qproc->mba_size);
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>