linux-kernel - Re: [PATCH V2] firmware: qcom_scm: use the SCM

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Message-ID: <2f915104-952f-3e3d-b3d5-4c0400b4f331@quicinc.com>
Date:   Tue, 20 Jun 2023 11:43:26 +0530
From:   Kathiravan T <quic_kathirav@...cinc.com>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Elliot Berman <eberman@...eaurora.org>,
        <linux-arm-msm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <quic_eberman@...cinc.com>, <stable@...r.kernel.org>
Subject: Re: [PATCH V2] firmware: qcom_scm: use the SCM_CONVENTION based on
 ARM / ARM64


On 6/7/2023 10:23 AM, Kathiravan T wrote:
> During SCM probe, to identify the SCM convention, scm call is made with
> SMC_CONVENTION_ARM_64 followed by SMC_CONVENTION_ARM_32. Based on the
> result what convention to be used is decided.
>
> IPQ chipsets starting from IPQ807x, supports both 32bit and 64bit kernel
> variants, however TZ firmware runs in 64bit mode. When running on 32bit
> kernel, scm call is made with SMC_CONVENTION_ARM_64 is causing the
> system crash, due to the difference in the register sets between ARM and
> AARCH64, which is accessed by the TZ.
>
> To avoid this, use SMC_CONVENTION_ARM_64 only on ARM64 builds.


Gentle Reminder...


>
> Cc: stable@...r.kernel.org
> Fixes: 9a434cee773a ("firmware: qcom_scm: Dynamically support SMCCC and legacy conventions")
> Signed-off-by: Kathiravan T <quic_kathirav@...cinc.com>
> ---
> Changes in V2:
> 	- Added the Fixes tag and cc'd stable mailing list
>
>   drivers/firmware/qcom_scm.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index fde33acd46b7..db6754db48a0 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -171,6 +171,7 @@ static enum qcom_scm_convention __get_convention(void)
>   	if (likely(qcom_scm_convention != SMC_CONVENTION_UNKNOWN))
>   		return qcom_scm_convention;
>   
> +#if IS_ENABLED(CONFIG_ARM64)
>   	/*
>   	 * Device isn't required as there is only one argument - no device
>   	 * needed to dma_map_single to secure world
> @@ -191,6 +192,7 @@ static enum qcom_scm_convention __get_convention(void)
>   		forced = true;
>   		goto found;
>   	}
> +#endif
>   
>   	probed_convention = SMC_CONVENTION_ARM_32;
>   	ret = __scm_smc_call(NULL, &desc, probed_convention, &res, true);