On Fri, 24 Sep 2021, 23:42 Stefano Stabellini, <sstabell...@kernel.org> wrote:
> On Fri, 24 Sep 2021, Rahul Singh wrote: > > Hi Stefano, > > > > > On 23 Sep 2021, at 8:12 pm, Stefano Stabellini <sstabell...@kernel.org> > wrote: > > > > > > On Thu, 23 Sep 2021, Rahul Singh wrote: > > >>>> + goto err_exit; > > >>>> + } > > >>> > > >>> This is unnecessary at the moment, right? Can we get rid of > ops->init ? > > >> > > >> No this is required for N1SDP board. Please check below patch. > > >> > https://gitlab.com/rahsingh/xen-integration/-/commit/6379ba5764df33d57547087cff4ffc078dc515d5 > > > > > > OK > > > > > > > > >>>> +int pci_host_common_probe(struct dt_device_node *dev, const void > *data) > > >>>> +{ > > >>>> + struct pci_host_bridge *bridge; > > >>>> + struct pci_config_window *cfg; > > >>>> + struct pci_ecam_ops *ops; > > >>>> + const struct dt_device_match *of_id; > > >>>> + int err; > > >>>> + > > >>>> + if ( dt_device_for_passthrough(dev) ) > > >>>> + return 0; > > >>>> + > > >>>> + of_id = dt_match_node(dev->dev.of_match_table, > dev->dev.of_node); > > >>>> + ops = (struct pci_ecam_ops *) of_id->data; > > >>> > > >>> Do we really need dt_match_node and dev->dev.of_match_table to get > > >>> dt_device_match.data? > > >>> > > >> > > >>> data is passed as a parameter to pci_host_common_probe, isn't it > enough > > >>> to do: > > >>> > > >>> ops = (struct pci_ecam_ops *) data; > > >> > > >> As of now not required but in future we might need it if we implement > other ecam supported bridge > > >> > > >> static const struct dt_device_match gen_pci_dt_match[] = { > > > >> { .compatible = "pci-host-ecam-generic", > > > >> .data = &pci_generic_ecam_ops }, > > >> > > >> { .compatible = "pci-host-cam-generic", > > >> .data = &gen_pci_cfg_cam_bus_ops }, > > > >> > > >> { }, > > > >> }; > > > > > > Even if we add another ECAM-supported bridge, the following: > > > > > > ops = (struct pci_ecam_ops *) data; > > > > > > could still work, right? The probe function will directly receive as > > > parameter the .data pointer. You shouldn't need the indirection via > > > dt_match_node? > > > > As per my understanding probe function will not get .data pointer.Probe > data argument is NULL in most of the cases in XEN > > Please have a look once dt_pci_init() -> device_init(..) call flow > implementation. > > You are right. Looking at the code, nobody is currently using > dt_device_match.data and it is clear why: it is not passed to the > device_desc.init function at all. As it is today, it is basically > useless. > IIRC it is used by the SMMU driver. But you need to lookup for the desc manually in each init callback. If I am not mistaken, this is how Linux is dealing with it as well. However... > And there is only one case where device_init has a non-NULL data > parameter and it is in xen/drivers/char/arm-uart.c. All the others are > not even using the data parameter of device_init. > I think we need to change device_init so that dt_device_match.data can > be useful. Sorry for the scope-creep but I think we should do the > following: > > - do not add of_match_table to struct device > > - add one more parameter to device_desc.init: > int (*init)(struct dt_device_node *dev, struct device_desc *desc, const > void *data); > > - change device_init to call desc->init with the right parameters: > desc->init(dev, desc, data); > > This way pci_host_common_probe is just going to get a desc directly as > parameter. I think it would make a lot more sense from an interface > perspective. It does require a change in all the DT_DEVICE_START.init > functions adding a struct device_desc *desc parameter, but it should be > a mechanical change. > > Alternatively we could just change device_init to pass > device_desc.dt_match.data when the data parameter is NULL but it feels > like a hack. > > > What do you think? ... I like the idea of passing desc parameter (we could also simply pass desc.data in an argument named "priv"). Cheers, >
