soc: qcom: rpmh-rsc: Ensure irqs aren't disabled by rpmh_rsc_send_data() callers

Dan pointed out that Smatch is concerned about this code because it uses
spin_lock_irqsave() and then calls wait_event_lock_irq() which enables
irqs before going to sleep. The comment above the function says it
should be called with interrupts enabled, but we simply hope that's true
without really confirming that. Let's add a might_sleep() here to
confirm that interrupts and preemption aren't disabled. Once we do that,
we can change the lock to be non-saving, spin_lock_irq(), to clarify
that we don't expect irqs to be disabled. If irqs are disabled by
callers they're going to be enabled anyway in the wait_event_lock_irq()
call which would be bad.

This should make Smatch happier and find bad callers faster with the
might_sleep(). We can drop the WARN_ON() in the caller because we have
the might_sleep() now, simplifying the code.
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/911181ed-c430-4592-ad26-4dc948834e08@moroto.mountain
Fixes: 2bc20f3c ("soc: qcom: rpmh-rsc: Sleep waiting for tcs slots to be free")
Cc: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20240509184129.3924422-1-swboyd@chromium.orgSigned-off-by: Bjorn Andersson <andersson@kernel.org>

drivers/soc/qcom/rpmh-rsc.c

@@ -646,13 +646,14 @@ int rpmh_rsc_send_data(struct rsc_drv *drv, const struct tcs_request *msg)
 {
 	struct tcs_group *tcs;
 	int tcs_id;
-	unsigned long flags;
+
+	might_sleep();
 
 	tcs = get_tcs_for_msg(drv, msg);
 	if (IS_ERR(tcs))
 		return PTR_ERR(tcs);
 
-	spin_lock_irqsave(&drv->lock, flags);
+	spin_lock_irq(&drv->lock);
 
 	/* Wait forever for a free tcs. It better be there eventually! */
 	wait_event_lock_irq(drv->tcs_wait,
@@ -670,7 +671,7 @@ int rpmh_rsc_send_data(struct rsc_drv *drv, const struct tcs_request *msg)
 		write_tcs_reg_sync(drv, drv->regs[RSC_DRV_CMD_ENABLE], tcs_id, 0);
 		enable_tcs_irq(drv, tcs_id, true);
 	}
-	spin_unlock_irqrestore(&drv->lock, flags);
+	spin_unlock_irq(&drv->lock);
 
 	/*
 	 * These two can be done after the lock is released because:

drivers/soc/qcom/rpmh.c

@@ -183,7 +183,6 @@ static int __rpmh_write(const struct device *dev, enum rpmh_state state,
 	}
 
 	if (state == RPMH_ACTIVE_ONLY_STATE) {
-		WARN_ON(irqs_disabled());
 		ret = rpmh_rsc_send_data(ctrlr_to_drv(ctrlr), &rpm_msg->msg);
 	} else {
 		/* Clean up our call by spoofing tx_done */