Subject: Re: [PATCH v8 38/45] powerpc/powernv: Functions to get/set PCI slot status

From: Alexey Kardashevskiy <[email-masked]>
Date: Wed, 20 Apr 2016 14:25:21 +1000

On 04/20/2016 12:36 PM, Gavin Shan wrote:
> On Tue, Apr 19, 2016 at 07:39:34PM +1000, Alexey Kardashevskiy wrote:
>> On 02/17/2016 02:44 PM, Gavin Shan wrote:
>>> This exports 4 functins, which base on the corresponding OPAL
>>
>>
>> s/functins/functions/
>>
>
> Thanks.
>
>>> APIs to get/set PCI slot status. Those functions are going to
>>> be used by PowerNV PCI hotplug driver:
>>>
>>>     pnv_pci_get_device_tree()    opal_get_device_tree()
>>>     pnv_pci_get_presence_state() opal_pci_get_presence_state()
>>>     pnv_pci_get_power_state()    opal_pci_get_power_state()
>>>     pnv_pci_set_power_state()    opal_pci_set_power_state()
>>>
>>> Besides, the patch also exports pnv_pci_hotplug_notifier_{register,
>>> unregister}() to allow registration and unregistration of PCI hotplug
>>> notifier, which will be used to receive PCI hotplug message from
>>> skiboot firmware in PowerNV PCI hotplug driver.
>>>
>>> Signed-off-by: Gavin Shan <[email-masked]>
>>> ---
>>>   arch/powerpc/include/asm/opal-api.h            | 17 ++++++-
>>>   arch/powerpc/include/asm/opal.h                |  4 ++
>>>   arch/powerpc/include/asm/pnv-pci.h             |  7 +++
>>>   arch/powerpc/platforms/powernv/opal-wrappers.S |  4 ++
>>>   arch/powerpc/platforms/powernv/pci.c           | 66 ++++++++++++++++++++++++++
>>>   5 files changed, 97 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/opal-api.h b/arch/powerpc/include/asm/opal-api.h
>>> index f8faaae..a6af338 100644
>>> --- a/arch/powerpc/include/asm/opal-api.h
>>> +++ b/arch/powerpc/include/asm/opal-api.h
>>> @@ -158,7 +158,11 @@
>>>   #define OPAL_LEDS_SET_INDICATOR			115
>>>   #define OPAL_CEC_REBOOT2			116
>>>   #define OPAL_CONSOLE_FLUSH			117
>>> -#define OPAL_LAST				117
>>> +#define OPAL_GET_DEVICE_TREE			118
>>> +#define OPAL_PCI_GET_PRESENCE_STATE		119
>>> +#define OPAL_PCI_GET_POWER_STATE		120
>>> +#define OPAL_PCI_SET_POWER_STATE		121
>>> +#define OPAL_LAST				121
>>>
>>>   /* Device tree flags */
>>>
>>> @@ -344,6 +348,16 @@ enum OpalPciResetState {
>>>   	OPAL_ASSERT_RESET   = 1
>>>   };
>>>
>>> +enum OpalPciSlotPresentenceState {
>>> +	OPAL_PCI_SLOT_EMPTY	= 0,
>>> +	OPAL_PCI_SLOT_PRESENT	= 1
>>> +};
>>> +
>>> +enum OpalPciSlotPowerState {
>>> +	OPAL_PCI_SLOT_POWER_OFF	= 0,
>>> +	OPAL_PCI_SLOT_POWER_ON	= 1
>>> +};
>>> +
>>>   enum OpalSlotLedType {
>>>   	OPAL_SLOT_LED_TYPE_ID = 0,	/* IDENTIFY LED */
>>>   	OPAL_SLOT_LED_TYPE_FAULT = 1,	/* FAULT LED */
>>> @@ -378,6 +392,7 @@ enum opal_msg_type {
>>>   	OPAL_MSG_DPO,
>>>   	OPAL_MSG_PRD,
>>>   	OPAL_MSG_OCC,
>>> +	OPAL_MSG_PCI_HOTPLUG,
>>>   	OPAL_MSG_TYPE_MAX,
>>>   };
>>>
>>> diff --git a/arch/powerpc/include/asm/opal.h b/arch/powerpc/include/asm/opal.h
>>> index 9e0039f..899bcb941 100644
>>> --- a/arch/powerpc/include/asm/opal.h
>>> +++ b/arch/powerpc/include/asm/opal.h
>>> @@ -209,6 +209,10 @@ int64_t opal_flash_write(uint64_t id, uint64_t offset, uint64_t buf,
>>>   		uint64_t size, uint64_t token);
>>>   int64_t opal_flash_erase(uint64_t id, uint64_t offset, uint64_t size,
>>>   		uint64_t token);
>>> +int64_t opal_get_device_tree(uint32_t phandle, uint64_t buf, uint64_t len);
>>> +int64_t opal_pci_get_presence_state(uint64_t id, uint8_t *state);
>>> +int64_t opal_pci_get_power_state(uint64_t id, uint8_t *state);
>>> +int64_t opal_pci_set_power_state(uint64_t id, uint8_t state);
>>>
>>>   /* Internal functions */
>>>   extern int early_init_dt_scan_opal(unsigned long node, const char *uname,
>>> diff --git a/arch/powerpc/include/asm/pnv-pci.h b/arch/powerpc/include/asm/pnv-pci.h
>>> index 6f77f71..d9d095b 100644
>>> --- a/arch/powerpc/include/asm/pnv-pci.h
>>> +++ b/arch/powerpc/include/asm/pnv-pci.h
>>> @@ -13,6 +13,13 @@
>>>   #include <linux/pci.h>
>>>   #include <misc/cxl-base.h>
>>>
>>> +extern int pnv_pci_get_device_tree(uint32_t phandle, void *buf, uint64_t len);
>>> +extern int pnv_pci_get_presence_state(uint64_t id, uint8_t *state);
>>> +extern int pnv_pci_get_power_state(uint64_t id, uint8_t *state);
>>> +extern int pnv_pci_set_power_state(uint64_t id, uint8_t state);
>>> +extern int pnv_pci_hotplug_notifier_register(struct notifier_block *nb);
>>> +extern int pnv_pci_hotplug_notifier_unregister(struct notifier_block *nb);
>>> +
>>>   int pnv_phb_to_cxl_mode(struct pci_dev *dev, uint64_t mode);
>>>   int pnv_cxl_ioda_msi_setup(struct pci_dev *dev, unsigned int hwirq,
>>>   			   unsigned int virq);
>>> diff --git a/arch/powerpc/platforms/powernv/opal-wrappers.S b/arch/powerpc/platforms/powernv/opal-wrappers.S
>>> index e45b88a..3ea1a855 100644
>>> --- a/arch/powerpc/platforms/powernv/opal-wrappers.S
>>> +++ b/arch/powerpc/platforms/powernv/opal-wrappers.S
>>> @@ -302,3 +302,7 @@ OPAL_CALL(opal_prd_msg,				OPAL_PRD_MSG);
>>>   OPAL_CALL(opal_leds_get_ind,			OPAL_LEDS_GET_INDICATOR);
>>>   OPAL_CALL(opal_leds_set_ind,			OPAL_LEDS_SET_INDICATOR);
>>>   OPAL_CALL(opal_console_flush,			OPAL_CONSOLE_FLUSH);
>>> +OPAL_CALL(opal_get_device_tree,			OPAL_GET_DEVICE_TREE);
>>> +OPAL_CALL(opal_pci_get_presence_state,		OPAL_PCI_GET_PRESENCE_STATE);
>>> +OPAL_CALL(opal_pci_get_power_state,		OPAL_PCI_GET_POWER_STATE);
>>> +OPAL_CALL(opal_pci_set_power_state,		OPAL_PCI_SET_POWER_STATE);
>>> diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
>>> index a458703..206385f 100644
>>> --- a/arch/powerpc/platforms/powernv/pci.c
>>> +++ b/arch/powerpc/platforms/powernv/pci.c
>>> @@ -63,6 +63,72 @@ int pnv_pci_poll(uint64_t id, int64_t rval, uint8_t *state)
>>>   	return (rval == OPAL_SUCCESS) ? 0 : -EIO;
>>>   }
>>>
>>> +int pnv_pci_get_device_tree(uint32_t phandle, void *buf, uint64_t len)
>>> +{
>>> +	int64_t rc;
>>> +
>>> +	if (!opal_check_token(OPAL_GET_DEVICE_TREE))
>>> +		return -ENXIO;
>>> +
>>> +	rc = opal_get_device_tree(phandle, (uint64_t)buf, len);
>>> +	if (rc != OPAL_SUCCESS)
>>> +		return -EIO;
>>> +
>>> +	return 0;
>>> +}
>>> +EXPORT_SYMBOL_GPL(pnv_pci_get_device_tree);
>>> +
>>> +int pnv_pci_get_presence_state(uint64_t id, uint8_t *state)
>>> +{
>>> +	int64_t rc;
>>> +
>>> +	if (!opal_check_token(OPAL_PCI_GET_PRESENCE_STATE))
>>> +		return -ENXIO;
>>> +
>>> +	rc = opal_pci_get_presence_state(id, state);
>>> +	if (rc != OPAL_SUCCESS)
>>> +		return -EIO;
>>> +
>>> +	return 0;
>>> +}
>>> +EXPORT_SYMBOL_GPL(pnv_pci_get_presence_state);
>>> +
>>> +int pnv_pci_get_power_state(uint64_t id, uint8_t *state)
>>> +{
>>> +	int64_t rc;
>>> +
>>> +	if (!opal_check_token(OPAL_PCI_GET_POWER_STATE))
>>> +		return -ENXIO;
>>> +
>>> +	rc = opal_pci_get_power_state(id, state);
>>
>>
>> Out of curiosity - if rc==OPAL_SUCCESS, @state should already contain the
>> correct state and you do not have to call pnv_pci_poll() (which will call
>> opal_pci_poll() immediately), is that correct?
>>
>
> It's not correct. opal_pci_get_power_state() to starts a state machine
> in the OPAL firmware and pnv_pci_poll() keeps pushing the state machine
> moving forward.

opal_pci_get_power_state() and pnv_pci_poll() both read the state, they do 
not push it (as they are not xxx_set or xxx_put or xxx_push) and there is 
no delay between these calls, does the state change so fast?

In practice, can this happen?
1. opal_pci_get_power_state() returns OPAL_SUCCESS and some state A;
2. pnv_pci_poll() called right-after-that-with-zero-delay (pnv_pci_poll() 
does not do loop if OPAL_SUCCESS) return a different state B.

Or these helpers return different types of states (unlikely though)?

It is not a concern but may help to understand all this OPAL polling magic.

>
>> Anyway, looks correct.
>>
>>
>> Reviewed-by: Alexey Kardashevskiy <[email-masked]>
>>
>>
>>
>>
>>> +	return pnv_pci_poll(id, rc, state);
>>> +}
>>> +EXPORT_SYMBOL_GPL(pnv_pci_get_power_state);
>>> +
>>> +int pnv_pci_set_power_state(uint64_t id, uint8_t state)
>>> +{
>>> +	int64_t rc;
>>> +
>>> +	if (!opal_check_token(OPAL_PCI_SET_POWER_STATE))
>>> +		return -ENXIO;
>>> +
>>> +	rc = opal_pci_set_power_state(id, state);
>>> +	return pnv_pci_poll(id, rc, NULL);
>>> +}
>>> +EXPORT_SYMBOL_GPL(pnv_pci_set_power_state);
>>> +
>>> +int pnv_pci_hotplug_notifier_register(struct notifier_block *nb)
>>> +{
>>> +	return opal_message_notifier_register(OPAL_MSG_PCI_HOTPLUG, nb);
>>> +}
>>> +EXPORT_SYMBOL_GPL(pnv_pci_hotplug_notifier_register);
>>> +
>>> +int pnv_pci_hotplug_notifier_unregister(struct notifier_block *nb)
>>> +{
>>> +	return opal_message_notifier_unregister(OPAL_MSG_PCI_HOTPLUG, nb);
>>> +}
>>> +EXPORT_SYMBOL_GPL(pnv_pci_hotplug_notifier_unregister);
>>> +
>>>   #ifdef CONFIG_PCI_MSI
>>>   int pnv_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
>>>   {
>>>
>>
>>
>> --
>> Alexey
>>
>
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>

-- 
Alexey