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SubjectRe: [PATCH v2 1/2] Revert "drivers: qcom: rpmh-rsc: Use rcuidle tracepoints for rpmh"
On Tue 25 Aug 06:21 CDT 2020, Maulik Shah wrote:

> 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@codeaurora.org>
> Cc: John Stultz <john.stultz@linaro.org>
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Reviewed-by: Stephen Boyd <swboyd@chromium.org>
> Reviewed-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Regards,
Bjorn

> Signed-off-by: Maulik Shah <mkshah@codeaurora.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);
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>

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