linux-kernel - Re: [PATCH] firmware: qcom: scm: Fix interrupted SCM calls fully

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Date:   Wed, 26 Oct 2016 11:35:08 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     andy.gross@...aro.org, Sricharan R <sricharan@...eaurora.org>
Cc:     patches@...aro.org, linux-arm-msm@...r.kernel.org,
        will.deacon@....com, stanimir.varbanov@...aro.org,
        linux-kernel@...r.kernel.org, srinivas.kandagatla@...aro.org,
        catalin.marinas@....com, sboyd@...eaurora.org
Subject: Re: [PATCH] firmware: qcom: scm: Fix interrupted SCM calls fully

On Wed 28 Sep 03:42 PDT 2016, Sricharan R wrote:

> Patch [1] fixes the issues with interrupted SCM64 calls
> by returning the register r6 (Session ID) on the next try, but register
> r0 also needs to be preserved for the retry. r0 contains the
> result of the previous try. Without this i see that the SCM calls
> hang when retried.
> 
> [1] https://patchwork.kernel.org/patch/9291589/
> 

Andy, this is needed as well on 8996 - or I get rcu stalls during
firmware loading operations (so I guess it's busy spinning in that
loop).

Tested-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Regards,
Bjorn

> Signed-off-by: Sricharan R <sricharan@...eaurora.org>
> ---
>  drivers/firmware/qcom_scm-64.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/firmware/qcom_scm-64.c b/drivers/firmware/qcom_scm-64.c
> index 7ecd0e7..28b604e 100755
> --- a/drivers/firmware/qcom_scm-64.c
> +++ b/drivers/firmware/qcom_scm-64.c
> @@ -134,6 +134,9 @@ static int qcom_scm_call(struct device *dev, u32 svc_id, u32 cmd_id,
>  		res->a6 = 0;
>  
>  		do {
> +			if (res->a0 == QCOM_SCM_INTERRUPTED)
> +				cmd = res->a0;
> +
>  			arm_smccc_smc(cmd, desc->arginfo, desc->args[0],
>  				      desc->args[1], desc->args[2], x5, res->a6, 0,
>  				      res);
> -- 
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
>