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SubjectRe: [PATCH v3 1/5] firmware: qcom_scm: provide a read-modify-write function
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On 17/03/2023 16:27, Mukesh Ojha wrote:
> It was released by Srinivas K. that there is a need of
> read-modify-write scm exported function so that it can
> be used by multiple clients.
>
> Let's introduce qcom_scm_io_update_field() which masks
> out the bits and write the passed value to that
> bit-offset. Subsequent patch will use this function.
>
> Suggested-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com>
> ---
> drivers/firmware/qcom_scm.c | 15 +++++++++++++++
> include/linux/firmware/qcom/qcom_scm.h | 2 ++
> 2 files changed, 17 insertions(+)
>
> diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> index 3e020d1..aca2556 100644
> --- a/drivers/firmware/qcom_scm.c
> +++ b/drivers/firmware/qcom_scm.c
> @@ -407,6 +407,21 @@ int qcom_scm_set_remote_state(u32 state, u32 id)
> }
> EXPORT_SYMBOL(qcom_scm_set_remote_state);
>
> +int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask, unsigned int val)
> +{
> + unsigned int old, new;
> + int ret;
> +
> + ret = qcom_scm_io_readl(addr, &old);
> + if (ret)
> + return ret;
> +
> + new = (old & ~mask) | val;

thanks for doing this,

With field semantics, val should be shifted within the function, so the
caller only sets value for field rather than passing a shifted value.
so this should be:

new = (old & ~mask) | (val << ffs(mask) - 1);


--srini



> +
> + return qcom_scm_io_writel(addr, new);
> +}
> +EXPORT_SYMBOL(qcom_scm_io_update_field);
> +
> static int __qcom_scm_set_dload_mode(struct device *dev, bool enable)
> {
> struct qcom_scm_desc desc = {
> diff --git a/include/linux/firmware/qcom/qcom_scm.h b/include/linux/firmware/qcom/qcom_scm.h
> index 1e449a5..203a781 100644
> --- a/include/linux/firmware/qcom/qcom_scm.h
> +++ b/include/linux/firmware/qcom/qcom_scm.h
> @@ -84,6 +84,8 @@ extern bool qcom_scm_pas_supported(u32 peripheral);
>
> extern int qcom_scm_io_readl(phys_addr_t addr, unsigned int *val);
> extern int qcom_scm_io_writel(phys_addr_t addr, unsigned int val);
> +extern int qcom_scm_io_update_field(phys_addr_t addr, unsigned int mask,
> + unsigned int val);
>
> extern bool qcom_scm_restore_sec_cfg_available(void);
> extern int qcom_scm_restore_sec_cfg(u32 device_id, u32 spare);

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