by Anshuman Khandual

[permalink] [raw]

Subject: Re: [PATCH V3 04/10] coresight: replicator: Move ACPI support from AMBA driver to platform driver

On 12/11/23 15:42, James Clark wrote:
>
>
> On 11/12/2023 07:51, Anshuman Khandual wrote:
>>
>>
>> On 12/8/23 11:09, Anshuman Khandual wrote:
>>> Add support for the dynamic replicator device in the platform driver, which
>>> can then be used on ACPI based platforms. This change would now allow
>>> runtime power management for repliacator devices on ACPI based systems.
>>>
>>> The driver would try to enable the APB clock if available. Also, rename the
>>> code to reflect the fact that it now handles both static and dynamic
>>> replicators.
>>>
>>> Cc: Lorenzo Pieralisi <[email protected]>
>>> Cc: Sudeep Holla <[email protected]>
>>> Cc: Suzuki K Poulose <[email protected]>
>>> Cc: Mike Leach <[email protected]>
>>> Cc: James Clark <[email protected]>
>>> Cc: [email protected]
>>> Cc: [email protected]
>>> Cc: [email protected]
>>> Cc: [email protected]
>>> Tested-by: Sudeep Holla <[email protected]> # Boot and driver probe only
>>> Acked-by: Sudeep Holla <[email protected]> # For ACPI related changes
>>> Signed-off-by: Anshuman Khandual <[email protected]>
>>> ---
>>> Changes in V3:
>>>
>>> - Added commnets for 'drvdata->pclk'
>>> - Used coresight_init_driver()/coresight_remove_driver() helpers instead
>>> - Dropped pm_runtime_put() from replicator_probe()
>>> - Added pm_runtime_put() on success path in dynamic_replicator_probe()
>>> - Added pm_runtime_put() on success/error paths in
>>> replicator_platform_probe()
>>>
>>> drivers/acpi/arm64/amba.c | 1 -
>>> .../coresight/coresight-replicator.c | 81 ++++++++++---------
>>> 2 files changed, 42 insertions(+), 40 deletions(-)
>>>
>>> diff --git a/drivers/acpi/arm64/amba.c b/drivers/acpi/arm64/amba.c
>>> index 171b5c2c7edd..270f4e3819a2 100644
>>> --- a/drivers/acpi/arm64/amba.c
>>> +++ b/drivers/acpi/arm64/amba.c
>>> @@ -27,7 +27,6 @@ static const struct acpi_device_id amba_id_list[] = {
>>> {"ARMHC503", 0}, /* ARM CoreSight Debug */
>>> {"ARMHC979", 0}, /* ARM CoreSight TPIU */
>>> {"ARMHC97C", 0}, /* ARM CoreSight SoC-400 TMC, SoC-600 ETF/ETB */
>>> - {"ARMHC98D", 0}, /* ARM CoreSight Dynamic Replicator */
>>> {"ARMHC9CA", 0}, /* ARM CoreSight CATU */
>>> {"ARMHC9FF", 0}, /* ARM CoreSight Dynamic Funnel */
>>> {"", 0},
>>> diff --git a/drivers/hwtracing/coresight/coresight-replicator.c b/drivers/hwtracing/coresight/coresight-replicator.c
>>> index b6be73034996..125b256cb8db 100644
>>> --- a/drivers/hwtracing/coresight/coresight-replicator.c
>>> +++ b/drivers/hwtracing/coresight/coresight-replicator.c
>>> @@ -31,6 +31,7 @@ DEFINE_CORESIGHT_DEVLIST(replicator_devs, "replicator");
>>> * @base: memory mapped base address for this component. Also indicates
>>> * whether this one is programmable or not.
>>> * @atclk: optional clock for the core parts of the replicator.
>>> + * @pclk: APB clock if present, otherwise NULL
>>> * @csdev: component vitals needed by the framework
>>> * @spinlock: serialize enable/disable operations.
>>> * @check_idfilter_val: check if the context is lost upon clock removal.
>>> @@ -38,6 +39,7 @@ DEFINE_CORESIGHT_DEVLIST(replicator_devs, "replicator");
>>> struct replicator_drvdata {
>>> void __iomem *base;
>>> struct clk *atclk;
>>> + struct clk *pclk;
>>> struct coresight_device *csdev;
>>> spinlock_t spinlock;
>>> bool check_idfilter_val;
>>> @@ -243,6 +245,10 @@ static int replicator_probe(struct device *dev, struct resource *res)
>>> return ret;
>>> }
>>>
>>> + drvdata->pclk = coresight_get_enable_apb_pclk(dev);
>>> + if (IS_ERR(drvdata->pclk))
>>> + return -ENODEV;
>>> +
>>> /*
>>> * Map the device base for dynamic-replicator, which has been
>>> * validated by AMBA core
>>> @@ -285,7 +291,6 @@ static int replicator_probe(struct device *dev, struct resource *res)
>>> }
>>>
>>> replicator_reset(drvdata);
>>> - pm_runtime_put(dev);
>>>
>>> out_disable_clk:
>>> if (ret && !IS_ERR_OR_NULL(drvdata->atclk))
>>> @@ -301,29 +306,31 @@ static int replicator_remove(struct device *dev)
>>> return 0;
>>> }
>>>
>>> -static int static_replicator_probe(struct platform_device *pdev)
>>> +static int replicator_platform_probe(struct platform_device *pdev)
>>> {
>>> + struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>> int ret;
>>>
>>> pm_runtime_get_noresume(&pdev->dev);
>>> pm_runtime_set_active(&pdev->dev);
>>> pm_runtime_enable(&pdev->dev);
>>>
>>> - /* Static replicators do not have programming base */
>>> - ret = replicator_probe(&pdev->dev, NULL);
>>> -
>>> - if (ret) {
>>> - pm_runtime_put_noidle(&pdev->dev);
>>> - pm_runtime_disable(&pdev->dev);
>>> - }
>>> + ret = replicator_probe(&pdev->dev, res);
>>> + pm_runtime_put(&pdev->dev);
>>
>> I believe pm_runtime_disable() would still be needed on the error path. Otherwise
>> pm_runtime_enable() will remain unbalanced on this error path when the replicator
>> module could not be loaded.
>>
>> --- a/drivers/hwtracing/coresight/coresight-replicator.c
>> +++ b/drivers/hwtracing/coresight/coresight-replicator.c
>> @@ -317,6 +317,8 @@ static int replicator_platform_probe(struct platform_device *pdev)
>>
>> ret = replicator_probe(&pdev->dev, res);
>> pm_runtime_put(&pdev->dev);
>> + if (ret)
>> + pm_runtime_disable(&pdev->dev);
>>
>> return ret;
>> }
>>
>> Similar constructs in this error path are also required in all other drivers (except
>> cpu debug) as well.
>
> Would that not need to be done as a fixes commit first with more detail
> about the issue if that's true? Maybe simulate the error and paste any
> error logs. For example etm4 already has this:

There are existing inconsistencies e.g between etm4 and replicator regarding
whether pm_runtime_disable() is called or not. So the idea here was to get
all remaining devices in line with replicator and debug devices method.

I don't have continuous access to an ACPI based coresight platform, creating
some challenges - although still trying to get access to such a system. But
wondering - it might be possible to simulate these success and error paths,
without having real ACPI based coresight platform devices.

>
> pm_runtime_get_noresume(&pdev->dev);
> pm_runtime_set_active(&pdev->dev);
> pm_runtime_enable(&pdev->dev);
>
> ret = etm4_probe(&pdev->dev);
>
> pm_runtime_put(&pdev->dev);
>
> I'm wondering if the disable is already covered by the platform code if
> the probe fails so no change is required?

AFAICT pm_runtime_enable()/pm_runtime_disable() goes in a pair for them to
remain balanced, there is a increasing/decreasing counter to ensure such a
balance is established and so without a corresponding pm_runtime_disable()
above etm4 path looks problematic. I guess this might just need fixing, as
a pre-requisite.

>
> if (drv->probe) {
> ret = drv->probe(dev);
> if (ret)
> dev_pm_domain_detach(_dev, true);
> }