Re: [PATCH v4 17/21] firmware: qcom_scm: provide a read-modify-write function

Pavan Kondeti
2023-06-30T05:01:51Z

On Wed, Jun 28, 2023 at 06:04:44PM +0530, Mukesh Ojha wrote:
> It was realized 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 fde33acd46b7..104d86e49b97 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 & mask);
> +
> + return qcom_scm_io_writel(addr, new);
> +}

I believe this API leaves the atomicity part to the client. or how does
it work?

Thanks,
Pavan