Messages in this thread | | | From | Peng Fan <> | Subject | RE: [PATCH V4 2/2] firmware: arm_scmi: add smc/hvc transport | Date | Wed, 4 Mar 2020 12:49:32 +0000 |
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Hi Sudeep,
> Subject: Re: [PATCH V4 2/2] firmware: arm_scmi: add smc/hvc transport > > On Tue, Mar 03, 2020 at 10:06:59AM +0800, peng.fan@nxp.com wrote: > > From: Peng Fan <peng.fan@nxp.com> > > > > 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@nxp.com> > > [...] > > > +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.
This is valid concern. But I think if shmem is shared bwteen protocols, the access to shmem should be protected in drivers/firmware/arm_scmi/driver.c: scmi_do_xfer, because send_message and fetch_response both touches shmem
The mailbox transport also has the issue you mentioned, I think.
Thanks, Peng. > > -- > Regards, > Sudeep
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