linux-kernel - Re: [PATCH v2 2/4] firmware: scm: Modify only the DLOAD bit in TCSR register for download mode

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Date:   Wed, 1 Mar 2023 12:39:36 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Mukesh Ojha <quic_mojha@...cinc.com>, agross@...nel.org,
        andersson@...nel.org, konrad.dybcio@...aro.org
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] firmware: scm: Modify only the DLOAD bit in TCSR
 register for download mode

On 01/03/2023 11:55, Mukesh Ojha 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.
> 
> Originally-by: Poovendhan Selvaraj <quic_poovendh@...cinc.com>
> Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> ---
> Changes in v2:
>   - Addressed comment made by Bjorn.
>   - Added download mask from patch 3 to this.
> 
>   drivers/firmware/qcom_scm.c | 17 +++++++++++++++--
>   1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index 51eb853..c9f1fad 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -27,6 +27,8 @@ module_param(download_mode, bool, 0);
>   #define SCM_HAS_IFACE_CLK	BIT(1)
>   #define SCM_HAS_BUS_CLK		BIT(2)
>   
> +#define QCOM_DOWNLOAD_MODE_MASK 0x30
> +
>   struct qcom_scm {
>   	struct device *dev;
>   	struct clk *core_clk;
> @@ -419,6 +421,7 @@ static void qcom_scm_set_download_mode(bool enable)
>   {
>   	bool avail;
>   	int ret = 0;
> +	u32 val;
>   
>   	avail = __qcom_scm_is_call_available(__scm->dev,
>   					     QCOM_SCM_SVC_BOOT,
> @@ -426,8 +429,18 @@ static void qcom_scm_set_download_mode(bool enable)
>   	if (avail) {
>   		ret = __qcom_scm_set_dload_mode(__scm->dev, 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_readl(__scm->dload_mode_addr, &val);
> +		if (ret) {
> +			dev_err(__scm->dev,
> +				"failed to read dload mode address value: %d\n", ret);
> +			return;
> +		}
> +
> +		val &= ~QCOM_DOWNLOAD_MODE_MASK;
> +		if (enable)
> +			val |= QCOM_SCM_BOOT_SET_DLOAD_MODE;
> +
> +		ret = qcom_scm_io_writel(__scm->dload_mode_addr, val);

Any locking for this RMW?

>   	} else {
>   		dev_err(__scm->dev,
>   			"No available mechanism for setting download mode\n");

-- 
With best wishes
Dmitry