Re: [PATCH V5 5/5] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

[Mukesh Ojha <quic_mojha@quicinc.com>]

On 2/16/2023 5:30 PM, 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@quicinc.com>
> Signed-off-by: Anusha Rao <quic_anusha@quicinc.com>
> Co-developed-by: Kathiravan Thirumoorthy <quic_kathirav@quicinc.com>
> Signed-off-by: Kathiravan Thirumoorthy <quic_kathirav@quicinc.com>
> Signed-off-by: Poovendhan Selvaraj <quic_poovendh@quicinc.com>
> ---
>   Changes in V5:
> 	- checking the return value in qcom_scm_set_download_mode function as
> 	  suggested by Srinivas Kandagatla
> 
>   Changes in V4:
> 	- retain the orginal value of tcsr register when download mode
> 	  is not set
> 
>   drivers/firmware/qcom_scm.c | 21 ++++++++++++++++-----
>   1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index 468d4d5ab550..d88c5f14bd54 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);
>   
>   	return qcom_scm_call_atomic(__scm->dev, &desc, NULL);
>   }
> @@ -426,15 +427,25 @@ 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);
> +
> +	if (ret) {
> +		dev_err(__scm->dev,
> +			"failed to read dload mode address value: %d\n", ret);
> +		return;
> +	}
> +
>   	if (avail) {
> -		ret = __qcom_scm_set_dload_mode(__scm->dev, enable);
> +		ret = __qcom_scm_set_dload_mode(__scm->dev, dload_addr_val, enable);

Did you test this on a target where it comes under this if statement? 
does it really need to know dload_mode_addr for this target ?

-Mukesh
>   	} 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");