Hi Lorenzo,
On Tuesday 01 May 2018 05:24 PM, Lorenzo Pieralisi wrote:
> On Tue, May 01, 2018 at 03:37:47PM +0530, Kishon Vijay Abraham I wrote:
>> Hi Lorenzo,
>>
>> On Thursday 26 April 2018 10:26 PM, Lorenzo Pieralisi wrote:
>>> On Tue, Apr 24, 2018 at 02:44:40PM +0100, Gustavo Pimentel wrote:
>>>> Adds a seconds entry on the pci_epf_test_ids structure that disables the
>>>
>>> "Add a second entry to..."
>>>
>>>> linkup_notifier parameter on driver for the designware EP.
>>>>
>>>> This allows designware EPs that doesn't have linkup notification signal
>>>> to work with pcitest.
>>>>
>>>> Updates the binding documentation accordingly.
>>>
>>> Valid for all the series: use imperative sentences.
>>>
>>> eg:
>>>
>>> "Update the binding documentation accordingly".
>>>
>>> not
>>>
>>> "Updates the binding documentation accordingly".
>>>
>>>> Signed-off-by: Gustavo Pimentel <gustavo.pimentel@xxxxxxxxxxxx>
>>>> Acked-by: Kishon Vijay Abraham I <kishon@xxxxxx>
>>>> ---
>>>> Change v2->v3:
>>>> - Added second entry in pci_epf_test_ids structure.
>>>> - Remove test_reg_bar field assignment on second entry.
>>>> Changes v3->v4:
>>>> - Nothing changed, just to follow the patch set version.
>>>> Changes v4->v5:
>>>> - Changed pci_epf_test_cfg2 to pci_epf_test_designware.
>>>> Changes v5->v6:
>>>> - Changed name field from pci_epf_test_designware to pci_epf_test_dw.
>>>> Changes v6->v7:
>>>> - Changed variable name from data_cfg2 to data_linkup_notifier_disabled.
>>>>
>>>> Documentation/PCI/endpoint/function/binding/pci-test.txt | 2 ++
>>>> drivers/pci/endpoint/functions/pci-epf-test.c | 8 ++++++++
>>>> 2 files changed, 10 insertions(+)
>>>>
>>>> diff --git a/Documentation/PCI/endpoint/function/binding/pci-test.txt b/Documentation/PCI/endpoint/function/binding/pci-test.txt
>>>> index 3b68b95..dc39f47 100644
>>>> --- a/Documentation/PCI/endpoint/function/binding/pci-test.txt
>>>> +++ b/Documentation/PCI/endpoint/function/binding/pci-test.txt
>>>> @@ -1,6 +1,8 @@
>>>> PCI TEST ENDPOINT FUNCTION
>>>>
>>>> name: Should be "pci_epf_test" to bind to the pci_epf_test driver.
>>>> +name: Should be "pci_epf_test_dw" to bind to the pci_epf_test driver
>>>> + with a custom configuration for the designware EP.
>>>
>>> The link between the "name" and the device created is quite obscure and
>>> reading pci-test-howto.txt certainly does not clarify it.
>>>
>>> In pci-test-howto.txt an explanation should be added to the configs
>>> device creation paragraph to clarify it.
>>>
>>>> Configurable Fields:
>>>> vendorid : should be 0x104c
>>>> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
>>>> index 7cef851..4ab463b 100644
>>>> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
>>>> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
>>>> @@ -459,10 +459,18 @@ static int pci_epf_test_bind(struct pci_epf *epf)
>>>> return 0;
>>>> }
>>>>
>>>> +static const struct pci_epf_test_data data_linkup_notifier_disabled = {
>>>> + .linkup_notifier = false
>>>> +};
>>>> +
>>>> static const struct pci_epf_device_id pci_epf_test_ids[] = {
>>>> {
>>>> .name = "pci_epf_test",
>>>> },
>>>> + {
>>>> + .name = "pci_epf_test_dw",
>>>> + .driver_data = (kernel_ulong_t)&data_linkup_notifier_disabled,
>>>> + },
>>>> {},
>>>
>>> Should not this be a property derived from the controller compatible
>>> property instead of the test device name written in configfs ?
>>
>> pci_epf_test is an independent driver on its own that operates in a layer above
>> the controller driver. So it does not get the controller compatible (which is
>> used in controller drivers like pcie-designware-plat.c). pci_epf_test uses
>> "pci_epf_device_id" which is _similar_ to "of_device_id" used by platform drivers.
>
> I understand that, the problem is that the independent driver depends on
> features of the related controller driver as this patch shows. This
> patch basically says that if you use a specific path in configfs (that
> includes pci_epf_test_dw) your device has specific HW features (eg
> linkup notifier above), that obviously depends on the platform HW not on
> the string you use in configfs.
>
> What I am questioning is a) if I understand this right and b) whether
> this is the right approach.
Your understanding is right. Ideally pci-epf-test driver shouldn't have any HW
specific configuration. But different HW have different configurations and
pci-epf-test should be informed of the configuration the HW supports.
configfs is just one way of creating epf_device and it was mainly added since
pci-epf-test cannot have a dt entry because it doesn't represent anything in
the HW.
The other option was to have a callback to EPC driver to get the features it
supports. But a particular feature that is required might be specific to a EPF
driver.
I find the driver_data approach in pci_epf_device_id to be more clean.
Thanks
Kishon
