linux-kernel - [PATCH v2 1/2] Revert "drivers: qcom: rpmh-rsc: Use rcuidle tracepoints for rpmh"

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Message-Id: <1598354482-15491-2-git-send-email-mkshah@codeaurora.org>
Date:   Tue, 25 Aug 2020 16:51:21 +0530
From:   Maulik Shah <mkshah@...eaurora.org>
To:     bjorn.andersson@...aro.org, andy.gross@...aro.org
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        ulf.hansson@...aro.org, swboyd@...omium.org, dianders@...omium.org,
        rnayak@...eaurora.org, ilina@...eaurora.org, lsrao@...eaurora.org,
        Maulik Shah <mkshah@...eaurora.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: [PATCH v2 1/2] Revert "drivers: qcom: rpmh-rsc: Use rcuidle tracepoints for rpmh"

Commit efde2659b0fe ("drivers: qcom: rpmh-rsc: Use rcuidle tracepoints
for rpmh") was written to fix a bug seen in an unmerged series that
implemented a struct generic_pm_domain::power_off() callback calling
rpmh_flush(). See stack trace below.

     Call trace:
      dump_backtrace+0x0/0x174
      show_stack+0x20/0x2c
      dump_stack+0xc8/0x124
      lockdep_rcu_suspicious+0xe4/0x104
      __tcs_buffer_write+0x230/0x2d0
      rpmh_rsc_write_ctrl_data+0x210/0x270
      rpmh_flush+0x84/0x24c
      rpmh_domain_power_off+0x78/0x98
      _genpd_power_off+0x40/0xc0
      genpd_power_off+0x168/0x208

Later the final merged solution is to use CPU PM notification to invoke
rpmh_flush() and power_off() callback of genpd is not implemented in the
driver.

CPU PM notifiers are run with RCU enabled/watching (see cpu_pm_notify()
and how it calls rcu_irq_enter_irqson() before calling the notifiers).

Remove this change since RCU will not be idle during CPU PM notifications
hence not required to use _rcuidle tracepoint. Using _rcuidle tracepoint
prevented rpmh driver to be loadable module as these are not exported
symbols.

This reverts commit efde2659b0fe835732047357b2902cca14f054d9.

Cc: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc: John Stultz <john.stultz@...aro.org>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>
Reviewed-by: Stephen Boyd <swboyd@...omium.org>
Reviewed-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Maulik Shah <mkshah@...eaurora.org>
---
 drivers/soc/qcom/rpmh-rsc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
index ae66757..fabe390d 100644
--- a/drivers/soc/qcom/rpmh-rsc.c
+++ b/drivers/soc/qcom/rpmh-rsc.c
@@ -495,7 +495,7 @@ static void __tcs_buffer_write(struct rsc_drv *drv, int tcs_id, int cmd_id,
 		write_tcs_cmd(drv, RSC_DRV_CMD_MSGID, tcs_id, j, msgid);
 		write_tcs_cmd(drv, RSC_DRV_CMD_ADDR, tcs_id, j, cmd->addr);
 		write_tcs_cmd(drv, RSC_DRV_CMD_DATA, tcs_id, j, cmd->data);
-		trace_rpmh_send_msg_rcuidle(drv, tcs_id, j, msgid, cmd);
+		trace_rpmh_send_msg(drv, tcs_id, j, msgid, cmd);
 	}
 
 	write_tcs_reg(drv, RSC_DRV_CMD_WAIT_FOR_CMPL, tcs_id, cmd_complete);
-- 
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