On Mon, Jan 08, 2024 at 08:57:31PM +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_rmw() which masks out the bits
> and write the passed value to that bit-offset.
>
> Suggested-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> Signed-off-by: Mukesh Ojha <quic_mojha@xxxxxxxxxxx>
> Tested-by: Kathiravan Thirumoorthy <quic_kathirav@xxxxxxxxxxx> # IPQ9574 and IPQ5332
> ---
> drivers/firmware/qcom/qcom_scm.c | 26 ++++++++++++++++++++++++++
> include/linux/firmware/qcom/qcom_scm.h | 1 +
> 2 files changed, 27 insertions(+)
>
> diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
> index 520de9b5633a..25549178a30f 100644
> --- a/drivers/firmware/qcom/qcom_scm.c
> +++ b/drivers/firmware/qcom/qcom_scm.c
> @@ -19,6 +19,7 @@
> #include <linux/of_irq.h>
> #include <linux/of_platform.h>
> #include <linux/platform_device.h>
> +#include <linux/spinlock.h>
> #include <linux/reset-controller.h>
> #include <linux/types.h>
>
> @@ -41,6 +42,8 @@ struct qcom_scm {
> int scm_vote_count;
>
> u64 dload_mode_addr;
> + /* Atomic context only */
> + spinlock_t lock;
IMHO, this comment can be confusing later. one might think that
qcom_scm_call_atomic() needs to be called with this lock, but that does
not seems to be the intention here.
> };
>
> struct qcom_scm_current_perm_info {
> @@ -481,6 +484,28 @@ static int qcom_scm_disable_sdi(void)
> return ret ? : res.result[0];
> }
>
> +int qcom_scm_io_rmw(phys_addr_t addr, unsigned int mask, unsigned int val)
> +{
> + unsigned int old, new;
> + int ret;
> +
> + if (!__scm)
> + return -EINVAL;
> +
> + spin_lock(&__scm->lock);
So, this function can't be called from hardirq context. If that ever
happens, with this new spinlock (without disabling interrupts), can
result in deadlock.
> + ret = qcom_scm_io_readl(addr, &old);
> + if (ret)
> + goto unlock;
> +
> + new = (old & ~mask) | (val & mask);
> +
> + ret = qcom_scm_io_writel(addr, new);
> +unlock:
> + spin_unlock(&__scm->lock);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(qcom_scm_io_rmw);
Thanks,
Pavan
