Re: [PATCH V4 2/2] firmware: arm_scmi: add smc/hvc transport

[Sudeep Holla]

On Tue, Mar 03, 2020 at 10:06:59AM +0800, peng.fan@xxxxxxx wrote:
> From: Peng Fan <peng.fan@xxxxxxx>
>
> Take arm,smc-id as the 1st arg, leave the other args as zero for now.
> There is no Rx, only Tx because of smc/hvc not support Rx.
>
> Signed-off-by: Peng Fan <peng.fan@xxxxxxx>

[...]

> +static int smc_send_message(struct scmi_chan_info *cinfo,
> +			    struct scmi_xfer *xfer)
> +{
> +	struct scmi_smc *scmi_info = cinfo->transport_info;
> +	struct arm_smccc_res res;
> +
> +	shmem_tx_prepare(scmi_info->shmem, xfer);

How do we protect another thread/process on another CPU going and
modifying the same shmem with another request ? We may need notion
of channel with associated shmem and it is protected with some lock.

--
Regards,
Sudeep