Re: [PATCH v7 3/5] remoteproc: Add support for runtime PM

From: Suman Anna
Date: Mon Jun 08 2020 - 20:48:31 EST

Hi Paul,

On 6/8/20 5:46 PM, Paul Cercueil wrote:
Hi Suman,

On 5/15/20 5:43 AM, Paul Cercueil wrote:
Call pm_runtime_get_sync() before the firmware is loaded, and
pm_runtime_put() after the remote processor has been stopped.

Even though the remoteproc device has no PM callbacks, this allows the
parent device's PM callbacks to be properly called.

I see this patch staged now for 5.8, and the latest -next branch has broken the pm-runtime autosuspend feature we have in the OMAP remoteproc driver. See commit 5f31b232c674 ("remoteproc/omap: Add support for runtime auto-suspend/resume").

What was the original purpose of this patch, because there can be differing backends across different SoCs.

Did you try pm_suspend_ignore_children()? It looks like it was made for your use-case.

Sorry for the delay in getting back. So, using pm_suspend_ignore_children() does fix my current issue.

But I still fail to see the original purpose of this patch in the remoteproc core especially given that the core itself does not have any callbacks. If the sole intention was to call the parent pdev's callbacks, then I feel that state-machine is better managed within that particular platform driver itself, as the sequencing/device management can vary with different platform drivers.

The problem is that with Ingenic SoCs some clocks must be enabled in order to load the firmware, and the core doesn't give you an option to register a callback to be called before loading it.

Yep, I have similar usage in one of my remoteproc drivers (see keystone_remoteproc.c), and I think this all stems from the need to use/support loading into a processor's internal memories. My driver does leverage the pm-clks backend plugged into pm_runtime, so you won't see explicit calls on the clocks.

I guess the question is what exact PM features you are looking for with the Ingenic SoC. I do see you are using pm_runtime autosuspend, and your callbacks are managing the clocks, but reset is managed only in start/stop.

The first version of my patchset added .prepare/.unprepare callbacks to the struct rproc_ops, but the feedback from the maintainers was that I should do it via runtime PM. However, it was not possible to keep it contained in the driver, since again the core doesn't provide a "prepare" callback, so no place to call pm_runtime_get_sync().

FWIW, the .prepare/.unprepare callbacks is actually now part of the rproc core. Looks like multiple developers had a need for this, and this functionality went in at the same time as your driver :). Not sure if you looked up the prior patches, I leveraged the patch that Loic had submitted a long-time ago, and a revised version of it is now part of 5.8-rc1.

So we settled with having runtime
PM in the core without callbacks, which will trigger the runtime PM callbacks of the driver at the right moment.

Looks like we can do some cleanup on the Ingenic SoC driver depending on the features you want.

regards
Suman


Sorry if that caused you trouble.

Cheers,
-Paul




Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
---

Notes:
ÂÂÂÂ v2-v4: No change
ÂÂÂÂ v5: Move calls to prepare/unprepare to rproc_fw_boot/rproc_shutdown
ÂÂÂÂ v6: Instead of prepare/unprepare callbacks, use PM runtime callbacks
ÂÂÂÂ v7: Check return value of pm_runtime_get_sync()

 drivers/remoteproc/remoteproc_core.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index a7f96bc98406..e33d1ef27981 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -29,6 +29,7 @@
 #include <linux/devcoredump.h>
 #include <linux/rculist.h>
 #include <linux/remoteproc.h>
+#include <linux/pm_runtime.h>
 #include <linux/iommu.h>
 #include <linux/idr.h>
 #include <linux/elf.h>
@@ -1382,6 +1383,12 @@ static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
ÂÂÂÂÂ if (ret)
ÂÂÂÂÂÂÂÂÂ return ret;
 + ret = pm_runtime_get_sync(dev);
+ÂÂÂ if (ret < 0) {
+ÂÂÂÂÂÂÂ dev_err(dev, "pm_runtime_get_sync failed: %d\n", ret);
+ÂÂÂÂÂÂÂ return ret;
+ÂÂÂ }
+
ÂÂÂÂÂ dev_info(dev, "Booting fw image %s, size %zd\n", name, fw->size);
  /*
@@ -1391,7 +1398,7 @@ static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
ÂÂÂÂÂ ret = rproc_enable_iommu(rproc);
ÂÂÂÂÂ if (ret) {
ÂÂÂÂÂÂÂÂÂ dev_err(dev, "can't enable iommu: %d\n", ret);
-ÂÂÂÂÂÂÂ return ret;
+ÂÂÂÂÂÂÂ goto put_pm_runtime;
ÂÂÂÂÂ }
  rproc->bootaddr = rproc_get_boot_addr(rproc, fw);
@@ -1435,6 +1442,8 @@ static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
ÂÂÂÂÂ rproc->table_ptr = NULL;
 disable_iommu:
ÂÂÂÂÂ rproc_disable_iommu(rproc);
+put_pm_runtime:
+ÂÂÂ pm_runtime_put(dev);
ÂÂÂÂÂ return ret;
 }
 @@ -1840,6 +1849,8 @@ void rproc_shutdown(struct rproc *rproc)
  rproc_disable_iommu(rproc);
 + pm_runtime_put(dev);
+
ÂÂÂÂÂ /* Free the copy of the resource table */
ÂÂÂÂÂ kfree(rproc->cached_table);
ÂÂÂÂÂ rproc->cached_table = NULL;
@@ -2118,6 +2129,9 @@ struct rproc *rproc_alloc(struct device *dev, const char *name,
  rproc->state = RPROC_OFFLINE;
 + pm_runtime_no_callbacks(&rproc->dev);
+ÂÂÂ pm_runtime_enable(&rproc->dev);
+
ÂÂÂÂÂ return rproc;
 }
 EXPORT_SYMBOL(rproc_alloc);
@@ -2133,6 +2147,7 @@ EXPORT_SYMBOL(rproc_alloc);
ÂÂ */
 void rproc_free(struct rproc *rproc)
 {
+ÂÂÂ pm_runtime_disable(&rproc->dev);
ÂÂÂÂÂ put_device(&rproc->dev);
 }
 EXPORT_SYMBOL(rproc_free);