soc: qcom: rpmh: Remove serialization of TCS commands

Requests sent to RPMH can be sent as fire-n-forget or response required,
with the latter ensuring the command has been completed by the hardware
accelerator. Commands in a request with tcs_cmd::wait set, would ensure
that those select commands are sent as response required, even though
the actual TCS request may be fire-n-forget.

Also, commands with .wait flag were also guaranteed to be complete
before the following command in the TCS is sent. This means that the
next command of the same request blocked until the current request is
completed. This could mean waiting for a voltage to settle or series of
NOCs be configured before the next command is sent. But drivers using
this feature have never cared about the serialization aspect. By not
enforcing the serialization we can allow the hardware to run in parallel
improving the performance.

Let's clarify the usage of this member in the tcs_cmd structure to mean
only completion and not serialization. This should also improve the
performance of bus requests where changes could happen in parallel.
Also, CPU resume from deep idle may see benefits from certain wake
requests.

Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Lina Iyer <ilina@codeaurora.org>
Signed-off-by: Maulik Shah <mkshah@codeaurora.org>
Link: https://lore.kernel.org/r/1610008770-13891-1-git-send-email-mkshah@codeaurora.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

1 files changed, 8 insertions, 1 deletions

diff --git a/include/soc/qcom/tcs.h b/include/soc/qcom/tcs.h
index 7a2a055ba6b0..3acca067c72b 100644
--- a/include/soc/qcom/tcs.h
+++ b/include/soc/qcom/tcs.h
@@ -30,7 +30,13 @@ enum rpmh_state {
  *
  * @addr: the address of the resource slv_id:18:16 | offset:0:15
  * @data: the resource state request
- * @wait: wait for this request to be complete before sending the next
+ * @wait: ensure that this command is complete before returning.
+ *        Setting "wait" here only makes sense during rpmh_write_batch() for
+ *        active-only transfers, this is because:
+ *        rpmh_write() - Always waits.
+ *                       (DEFINE_RPMH_MSG_ONSTACK will set .wait_for_compl)
+ *        rpmh_write_async() - Never waits.
+ *                       (There's no request completion callback)
  */
 struct tcs_cmd {
 	u32 addr;
@@ -43,6 +49,7 @@ struct tcs_cmd {
  *
  * @state:          state for the request.
  * @wait_for_compl: wait until we get a response from the h/w accelerator
+ *                  (same as setting cmd->wait for all commands in the request)
  * @num_cmds:       the number of @cmds in this request
  * @cmds:           an array of tcs_cmds
  */