Re: [PATCH V4 4/6] coresight: etm4x: Change etm4_platform_driver driver for MMIO devices

[Anshuman Khandual <anshuman.khandual@arm.com>]

On 5/26/23 02:53, Suzuki K Poulose wrote:
> Hi Anshuman
> 
> Please find a minor issue with the clock handling below.
> 
> On 23/05/2023 05:45, Anshuman Khandual wrote:
>> Add support for handling MMIO based devices via platform driver. We need to
>> make sure that :
>>
>> 1) The APB clock, if present is enabled at probe and via runtime_pm ops
>> 2) Use the ETM4x architecture or CoreSight architecture registers to
>>     identify a device as CoreSight ETM4x, instead of relying a white list of
>>     "Peripheral IDs"
>>
>> The driver doesn't get to handle the devices yet, until we wire the ACPI
>> changes to move the devices to be handled via platform driver than the
>> etm4_amba driver.
>>
>> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
>> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
>> Cc: Mike Leach <mike.leach@linaro.org>
>> Cc: Leo Yan <leo.yan@linaro.org>
>> Cc: coresight@lists.linaro.org
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: linux-kernel@vger.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
>> ---
>>   .../coresight/coresight-etm4x-core.c          | 57 ++++++++++++++++++-
>>   drivers/hwtracing/coresight/coresight-etm4x.h |  4 ++
>>   include/linux/coresight.h                     | 47 +++++++++++++++
>>   3 files changed, 106 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
>> index 57a7181017bd..c9e2219ee6b6 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
>> @@ -30,6 +30,7 @@
>>   #include <linux/platform_device.h>
>>   #include <linux/pm_runtime.h>
>>   #include <linux/property.h>
>> +#include <linux/clk/clk-conf.h>
>>     #include <asm/barrier.h>
>>   #include <asm/sections.h>
>> @@ -1073,11 +1074,21 @@ static bool etm4_init_sysreg_access(struct etmv4_drvdata *drvdata,
>>       return true;
>>   }
>>   +static bool is_devtype_cpu_trace(void __iomem *base)
>> +{
>> +    u32 devtype = readl(base + TRCDEVTYPE);
>> +
>> +    return (devtype == CS_DEVTYPE_PE_TRACE);
>> +}
>> +
>>   static bool etm4_init_iomem_access(struct etmv4_drvdata *drvdata,
>>                      struct csdev_access *csa)
>>   {
>>       u32 devarch = readl_relaxed(drvdata->base + TRCDEVARCH);
>>   +    if (!is_coresight_device(drvdata->base) || !is_devtype_cpu_trace(drvdata->base))
>> +        return false;
>> +
>>       /*
>>        * All ETMs must implement TRCDEVARCH to indicate that
>>        * the component is an ETMv4. Even though TRCIDR1 also
>> @@ -2135,6 +2146,7 @@ static int etm4_probe_amba(struct amba_device *adev, const struct amba_id *id)
>>     static int etm4_probe_platform_dev(struct platform_device *pdev)
>>   {
>> +    struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>       struct etmv4_drvdata *drvdata;
>>       int ret;
>>   @@ -2142,7 +2154,18 @@ static int etm4_probe_platform_dev(struct platform_device *pdev)
>>       if (!drvdata)
>>           return -ENOMEM;
>>   -    drvdata->base = NULL;
>> +    drvdata->pclk = coresight_get_enable_apb_pclk(&pdev->dev);
>> +    if (IS_ERR(drvdata->pclk))
>> +        return -ENODEV;
>> +
>> +    if (res) {
>> +        drvdata->base = devm_ioremap_resource(&pdev->dev, res);
>> +        if (IS_ERR(drvdata->base)) {
>> +            clk_put(drvdata->pclk);
> 
> clk_put() can handle drvdata->pclk == NULL and bail out early. So calling this without the != NULL check is fine.
> 
>> +            return PTR_ERR(drvdata->base);
>> +        }
>> +    }
>> +
>>       dev_set_drvdata(&pdev->dev, drvdata);
>>       pm_runtime_get_noresume(&pdev->dev);
>>       pm_runtime_set_active(&pdev->dev);
>> @@ -2188,7 +2211,7 @@ static struct amba_cs_uci_id uci_id_etm4[] = {
>>           /*  ETMv4 UCI data */
>>           .devarch    = ETM_DEVARCH_ETMv4x_ARCH,
>>           .devarch_mask    = ETM_DEVARCH_ID_MASK,
>> -        .devtype    = 0x00000013,
>> +        .devtype    = CS_DEVTYPE_PE_TRACE,
>>       }
>>   };
>>   @@ -2247,6 +2270,9 @@ static int __exit etm4_remove_platform_dev(struct platform_device *pdev)
>>       if (drvdata)
>>           ret = etm4_remove_dev(drvdata);
>>       pm_runtime_disable(&pdev->dev);
>> +
>> +    if (drvdata->pclk)
>> +        clk_put(drvdata->pclk);
>>       return ret;
>>   }
>>   @@ -2286,6 +2312,32 @@ static struct amba_driver etm4x_amba_driver = {
>>       .id_table    = etm4_ids,
>>   };
>>   +#ifdef CONFIG_PM
>> +static int etm4_runtime_suspend(struct device *dev)
>> +{
>> +    struct etmv4_drvdata *drvdata = dev_get_drvdata(dev);
>> +
>> +    if (!IS_ERR(drvdata->pclk))
>> +        clk_disable_unprepare(drvdata->pclk);
> 
> However this seems to be inconsistent. Should we not use:
> 
>     if (drvdata->pclk)
>         ...

This makes sense, will update the condition check as follows.

--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -2318,7 +2318,7 @@ static int etm4_runtime_suspend(struct device *dev)
 {
        struct etmv4_drvdata *drvdata = dev_get_drvdata(dev);
 
-       if (!IS_ERR(drvdata->pclk))
+       if (drvdata->pclk && !IS_ERR(drvdata->pclk))
                clk_disable_unprepare(drvdata->pclk);
 
        return 0;
@@ -2328,7 +2328,7 @@ static int etm4_runtime_resume(struct device *dev)
 {
        struct etmv4_drvdata *drvdata = dev_get_drvdata(dev);
 
-       if (!IS_ERR(drvdata->pclk))
+       if (drvdata->pclk && !IS_ERR(drvdata->pclk))
                clk_prepare_enable(drvdata->pclk);
 
        return 0;

> 
>> +
>> +    return 0;
>> +}
>> +
>> +static int etm4_runtime_resume(struct device *dev)
>> +{
>> +    struct etmv4_drvdata *drvdata = dev_get_drvdata(dev);
>> +
>> +    if (!IS_ERR(drvdata->pclk))
> 
> same as above ?
> 
>> +        clk_prepare_enable(drvdata->pclk);
>> +
>> +    return 0;
>> +}
>> +#endif
>> +
>> +static const struct dev_pm_ops etm4_dev_pm_ops = {
>> +    SET_RUNTIME_PM_OPS(etm4_runtime_suspend, etm4_runtime_resume, NULL)
>> +};
>> +
>>   static const struct of_device_id etm4_sysreg_match[] = {
>>       { .compatible    = "arm,coresight-etm4x-sysreg" },
>>       { .compatible    = "arm,embedded-trace-extension" },
>> @@ -2299,6 +2351,7 @@ static struct platform_driver etm4_platform_driver = {
>>           .name            = "coresight-etm4x",
>>           .of_match_table        = etm4_sysreg_match,
>>           .suppress_bind_attrs    = true,
>> +        .pm            = &etm4_dev_pm_ops,
>>       },
>>   };
>>   diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
>> index 27c8a9901868..0ff0bd2cd504 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
>> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
>> @@ -701,6 +701,8 @@
>>   #define ETM_DEVARCH_ETE_ARCH                        \
>>       (ETM_DEVARCH_ARCHITECT_ARM | ETM_DEVARCH_ARCHID_ETE | ETM_DEVARCH_PRESENT)
>>   +#define CS_DEVTYPE_PE_TRACE        0x00000013
>> +
>>   #define TRCSTATR_IDLE_BIT        0
>>   #define TRCSTATR_PMSTABLE_BIT        1
>>   #define ETM_DEFAULT_ADDR_COMP        0
>> @@ -944,6 +946,7 @@ struct etmv4_save_state {
>>     /**
>>    * struct etm4_drvdata - specifics associated to an ETM component
>> + * @pclk        APB clock for this component
> 
> Might be worth adding the comment here :
> 
>      * @pclk:        APB clock if present, otherwise NULL

Sure, will update this comment above.

> 
> Rest looks fine to me
> 
> Suzuki

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