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SubjectRe: [RFC][PATCH V4] axi: add AXI bus driver
From
2011/4/13 George Kashperko <george@znau.edu.ua>:
>
>> 2011/4/13 George Kashperko <george@znau.edu.ua>:
>> >
>> > В Срд, 13/04/2011 в 21:39 +0200, Rafał Miłecki пишет:
>> >> 2011/4/13 Greg KH <greg@kroah.com>:
>> >> >> diff --git a/drivers/axi/axi_pci_bridge.c b/drivers/axi/axi_pci_bridge.c
>> >> >> new file mode 100644
>> >> >> index 0000000..17e882c
>> >> >> --- /dev/null
>> >> >> +++ b/drivers/axi/axi_pci_bridge.c
>> >> >> @@ -0,0 +1,33 @@
>> >> >> +/*
>> >> >> + * AXI PCI bridge module
>> >> >> + *
>> >> >> + * Licensed under the GNU/GPL. See COPYING for details.
>> >> >> + */
>> >> >> +
>> >> >> +#include "axi_private.h"
>> >> >> +
>> >> >> +#include <linux/axi/axi.h>
>> >> >> +#include <linux/pci.h>
>> >> >> +
>> >> >> +static DEFINE_PCI_DEVICE_TABLE(axi_pci_bridge_tbl) = {
>> >> >> +     { PCI_DEVICE(PCI_VENDOR_ID_BROADCOM, 0x4331) },
>> >> >> +     { PCI_DEVICE(PCI_VENDOR_ID_BROADCOM, 0x4353) },
>> >> >> +     { PCI_DEVICE(PCI_VENDOR_ID_BROADCOM, 0x4727) },
>> >> >> +     { 0, },
>> >> >> +};
>> >> >> +MODULE_DEVICE_TABLE(pci, axi_pci_bridge_tbl);
>> >> >> +
>> >> >> +static struct pci_driver axi_pci_bridge_driver = {
>> >> >> +     .name = "axi-pci-bridge",
>> >> >> +     .id_table = axi_pci_bridge_tbl,
>> >> >> +};
>> >> >> +
>> >> >> +int __init axi_pci_bridge_init(void)
>> >> >> +{
>> >> >> +     return axi_host_pci_register(&axi_pci_bridge_driver);
>> >> >> +}
>> >> >> +
>> >> >> +void __exit axi_pci_bridge_exit(void)
>> >> >> +{
>> >> >> +     axi_host_pci_unregister(&axi_pci_bridge_driver);
>> >> >> +}
>> >> >
>> >> > You register a pci driver that does nothing?  That's not right, you need
>> >> > to then base your axi bus off of that pci device, so it is hooked up
>> >> > correctly in the /sys/devices/ tree.  Otherwise you are somewhere up in
>> >> > the virtual location for your axi bus, right?
>> >>
>> >> Please take a look at:
>> >> driver->probe = axi_host_pci_probe;
>> >> driver->remove = axi_host_pci_remove;
>> >> return pci_register_driver(driver);
>> >>
>> >>
>> >> >> +bool axi_core_is_enabled(struct axi_device *core)
>> >> >> +{
>> >> >> +     if ((axi_aread32(core, AXI_IOCTL) & (AXI_IOCTL_CLK | AXI_IOCTL_FGC))
>> >> >> +         != AXI_IOCTL_CLK)
>> >> >> +             return false;
>> >> >> +     if (axi_aread32(core, AXI_RESET_CTL) & AXI_RESET_CTL_RESET)
>> >> >> +             return false;
>> >> >> +     return true;
>> >> >> +}
>> >> >> +EXPORT_SYMBOL(axi_core_is_enabled);
>> >> >
>> >> > EXPORT_SYMBOL_GPL()?
>> >> >
>> >> > What module uses this?  And why would it care?
>> >> >
>> >> >> +EXPORT_SYMBOL(axi_core_enable);
>> >> >
>> >> > EXPORT_SYMBOL_GPL()?
>> >> >
>> >> > Same goes for your other exports, just want you to be sure here.
>> >>
>> >> Hm, I'm not sure. Using EXPORT_SYMBOL_GPL will forbid closed source
>> >> drivers from using our bus driver, right? I'm don't have preferences
>> >> on this, if you prefer us to force GPL, I can.
>> >>
>> >>
>> >> >> +u32 xaxi_chipco_gpio_control(struct axi_drv_cc *cc, u32 mask, u32 value)
>> >> >> +{
>> >> >> +     return axi_cc_write32_masked(cc, AXI_CC_GPIOCTL, mask, value);
>> >> >> +}
>> >> >> +EXPORT_SYMBOL(xaxi_chipco_gpio_control);
>> >> >
>> >> > "xaxi"?  Shouldn't that be consistant with the other exports and start
>> >> > with "axi"?
>> >>
>> >> Left from old tests/rewrites/splitting. Thanks.
>> >>
>> >>
>> >> >> +static u8 axi_host_pci_read8(struct axi_device *core, u16 offset)
>> >> >> +{
>> >> >> +     if (unlikely(core->bus->mapped_core != core))
>> >> >
>> >> > Are you sure about the use of unlikely in this, and other functions?
>> >> > The compiler almost always does a better job than we do for these types
>> >> > of calls, just let it do it's job.
>> >> >
>> >> >> +             axi_host_pci_switch_core(core);
>> >> >> +     return ioread8(core->bus->mmio + offset);
>> >> >
>> >> > I think because of that unlikely, you just slowed down all pci devices,
>> >> > right?  That's not very nice :)
>> >>
>> >> Hm, my logic suggests it is alright, but please consider this once
>> >> more with me ;)
>> >>
>> >> For the most of the time mapped_core (active core) do not change. We
>> >> perform few hundreds of operations on one core in a row. This way
>> >> mapped_core points to passed core for most of the time. Condition
>> >> (mapped_core != core) is unlikely to happen.
>> >>
>> >> Is there anything wrong in my logic?
>> >>
>> > Yes, there is. You don't need that "if" at all.
>>
>> Damn, WHY do you make me ask why, why, why, all the time?! Can't you
>> just write word of explanation without being asked for?
>>
> Errm... Sorry, but I've already explained PCIE host behaviour _several_
> times several days ago. Personally I like to ask questions. Have
> absolutely nothing agains anyone else asking good questions. Never try
> to make people ask me questions I know they would ask anyway. Really you
> might missed some my messages earlier or maybe my english is too awful ?
>
> Yet again, for PCIE cores (not only for them, for some PCI cores as
> well) buscommon, buscore and function core are all available
> simultaneously. You dont need window sliding when access them.

I had no idea what you were referring to. We do not dig into PCIe
functions yet, so I believe for now we need this "if".

I'm getting totally frustrated with that whole situation :|

--
Rafał
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