linux-kernel - Re: [PATCH V4 5/5] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

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Message-ID: <ffeff1f8-ebf6-3115-38d1-fa318549baa0@linaro.org>
Date:   Tue, 14 Feb 2023 12:57:39 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Poovendhan Selvaraj <quic_poovendh@...cinc.com>, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, lee@...nel.org,
        mturquette@...libre.com, sboyd@...nel.org,
        jassisinghbrar@...il.com, catalin.marinas@....com, will@...nel.org,
        shawnguo@...nel.org, arnd@...db.de, marcel.ziswiler@...adex.com,
        robimarko@...il.com, dmitry.baryshkov@...aro.org,
        nfraprado@...labora.com, broonie@...nel.org,
        quic_gurus@...cinc.com, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     quic_srichara@...cinc.com, quic_gokulsri@...cinc.com,
        quic_sjaganat@...cinc.com, quic_kathirav@...cinc.com,
        quic_arajkuma@...cinc.com, quic_anusha@...cinc.com,
        quic_devipriy@...cinc.com
Subject: Re: [PATCH V4 5/5] firmware: scm: Modify only the DLOAD bit in TCSR
 register for download mode



On 14/02/2023 05:14, Poovendhan Selvaraj wrote:
> CrashDump collection is based on the DLOAD bit of TCSR register.
> To retain other bits, we read the register and modify only the DLOAD bit as
> the other bits have their own significance.
> 
> Co-developed-by: Anusha Rao <quic_anusha@...cinc.com>
> Signed-off-by: Anusha Rao <quic_anusha@...cinc.com>
> Co-developed-by: Kathiravan Thirumoorthy <quic_kathirav@...cinc.com>
> Signed-off-by: Kathiravan Thirumoorthy <quic_kathirav@...cinc.com>
> Signed-off-by: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
> ---
>   Changes in V4:
> 	- retain the orginal value of tcsr register when download mode
> 	  is not set
> 
>   drivers/firmware/qcom_scm.c | 15 ++++++++++-----
>   1 file changed, 10 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index 468d4d5ab550..8a34b386ac3a 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -407,7 +407,7 @@ int qcom_scm_set_remote_state(u32 state, u32 id)
>   }
>   EXPORT_SYMBOL(qcom_scm_set_remote_state);
>   
> -static int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
> +static int __qcom_scm_set_dload_mode(struct device *dev, u32 val, bool enable)
>   {
>   	struct qcom_scm_desc desc = {
>   		.svc = QCOM_SCM_SVC_BOOT,
> @@ -417,7 +417,8 @@ static int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
>   		.owner = ARM_SMCCC_OWNER_SIP,
>   	};
>   
> -	desc.args[1] = enable ? QCOM_SCM_BOOT_SET_DLOAD_MODE : 0;
> +	desc.args[1] = enable ? val | QCOM_SCM_BOOT_SET_DLOAD_MODE :
> +				val & ~(QCOM_SCM_BOOT_SET_DLOAD_MODE);

why not read the value here before setting the DLOAD Mode instead of 
doing it in qcom_scm_set_download_mode()?
that would make the code simple and readable.



>   
>   	return qcom_scm_call_atomic(__scm->dev, &desc, NULL);
>   }
> @@ -426,15 +427,19 @@ static void qcom_scm_set_download_mode(bool enable)
>   {
>   	bool avail;
>   	int ret = 0;
> +	u32 dload_addr_val;
>   
>   	avail = __qcom_scm_is_call_available(__scm->dev,
>   					     QCOM_SCM_SVC_BOOT,
>   					     QCOM_SCM_BOOT_SET_DLOAD_MODE);
> +	ret = qcom_scm_io_readl(__scm->dload_mode_addr, &dload_addr_val);
> +
not checking ret value here before proceeding?

>   	if (avail) {
> -		ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
> +		ret = __qcom_scm_set_dload_mode(__scm->dev, dload_addr_val, enable);
>   	} else if (__scm->dload_mode_addr) {
> -		ret = qcom_scm_io_writel(__scm->dload_mode_addr,
> -				enable ? QCOM_SCM_BOOT_SET_DLOAD_MODE : 0);
> +		ret = qcom_scm_io_writel(__scm->dload_mode_addr, enable ?
> +				dload_addr_val | QCOM_SCM_BOOT_SET_DLOAD_MODE :
> +				dload_addr_val & ~(QCOM_SCM_BOOT_SET_DLOAD_MODE));
>   	} else {
>   		dev_err(__scm->dev,
>   			"No available mechanism for setting download mode\n");