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But, it might not be. Both the kernel driver and GSP communicate > with FSP. The way they should attempt to keep exclusive access to this > channel to FSP is by making sure they don't try to start writing if > there's pending data until the full round trip has finished. > > Signed-off-by: Eliot Courtney > --- > drivers/gpu/nova-core/falcon/fsp.rs | 23 +++++++++++++++++++++++ > 1 file changed, 23 insertions(+) > > diff --git a/drivers/gpu/nova-core/falcon/fsp.rs b/drivers/gpu/nova-core/= falcon/fsp.rs > index 21eaa8e261ce..cdb476894e1a 100644 > --- a/drivers/gpu/nova-core/falcon/fsp.rs > +++ b/drivers/gpu/nova-core/falcon/fsp.rs > @@ -125,6 +125,26 @@ fn poll_msgq(&self, bar: Bar0<'_>) -> Result { > } > } > =20 > + /// Both the kernel driver and GSP talk to FSP. Try to ensure exclus= ive access to the FSP is > + /// enforced by making sure there is not a pending message already s= ent to FSP, and that there > + /// is no pending message from FSP to be read. > + fn wait_until_ready(&mut self, bar: Bar0<'_>) -> Result { > + read_poll_timeout( > + || { > + let qhead =3D bar.read(regs::NV_PFSP_QUEUE_HEAD::at(0)).= address(); > + let qtail =3D bar.read(regs::NV_PFSP_QUEUE_TAIL::at(0)).= address(); > + let mhead =3D bar.read(regs::NV_PFSP_MSGQ_HEAD::at(0)).v= al(); > + let mtail =3D bar.read(regs::NV_PFSP_MSGQ_TAIL::at(0)).v= al(); How does this prevent race between kernel and GSP when initiating FSP communcation? Best, Gary > + > + Ok(qhead =3D=3D qtail && mhead =3D=3D mtail) > + }, > + |&ready| ready, > + Delta::from_millis(10), > + Delta::from_millis(FSP_MSG_TIMEOUT_MS), > + )?; > + Ok(()) > + } > + > /// Writes `packet` to FSP EMEM and updates the queue pointers to no= tify FSP. > /// > /// Returns `EINVAL` if `packet` is empty or its length is not 4-byt= e aligned. > @@ -133,6 +153,9 @@ pub(crate) fn send_msg(&mut self, bar: Bar0<'_>, pack= et: &[u8]) -> Result { > return Err(EINVAL); > } > =20 > + // Try to make sure we have exclusive access to the FSP at this = point. > + self.wait_until_ready(bar)?; > + > self.write_emem(bar, packet)?; > =20 > // Update queue pointers. TAIL points at the last DWORD written.