Hi, Alex, On 2017/2/1 3:37, Alexander Graf wrote: > > > On 31/01/2017 14:32, John Garry wrote: >> On 30/01/2017 17:12, Alexander Graf wrote: >>> On 01/24/2017 08:05 AM, zhichang.yuan wrote: >>>> Low-pin-count interface is integrated into some SoCs. The accesses to >>>> those >>>> peripherals under LPC make use of I/O ports rather than the memory >>>> mapped I/O. >>>> >>>> To drive these devices, this patch introduces a method named >>>> indirect-IO. >>>> In this method the in/out() accessor in include/asm-generic/io.h will be >>>> redefined. When upper layer drivers call in/out() with those known >>>> legacy port >>>> addresses to access the peripherals, the I/O operations will be routed >>>> to the >>>> right hooks which are registered specific to the host device, such as >>>> LPC. >>>> Then the hardware relevant manupulations are finished by the >>>> corresponding >>>> host. >>>> >>>> According to the comments on V5, this patch adds a common indirect-IO >>>> driver >>>> which support this I/O indirection to the generic directory. >>>> >>>> In the later pathches, some host-relevant drivers are implemented to >>>> support >>>> the specific I/O hooks and register them. >>>> Based on these, the upper layer drivers which depend on in/out() can >>>> work well >>>> without any extra work or any changes. >>>> >>>> Signed-off-by: zhichang.yuan <yuanzhichang@xxxxxxxxxxxxx> >>>> Signed-off-by: Gabriele Paoloni <gabriele.paoloni@xxxxxxxxxx> >>>> Signed-off-by: John Garry <john.garry@xxxxxxxxxx> >>> >>> I like the extio idea. That allows us to handle all PIO requests on >>> platforms that don't have native PIO support via different routes >>> depending on the region they're in. Unfortunately we now we have 2 >>> frameworks for handling sparse PIO regions: One in extio, one in PCI. >>> >>> Why don't we just merge the two? Most of the code that has #ifdef >>> PCI_IOBASE throughout the code base sounds like an ideal candidate to >>> get migrated to extio instead. Then we only have a single framework to >>> worry about ... >> >> To be clear, are you suggesting we merge the functionality from >> pci_register_io_range(), pci_pio_to_address(), pci_address_to_pio() into >> extio, so extio manages all PIO? > > Yes, I guess so. > >> And having a single type of node to >> register PIO ranges, by amalgamating struct extio_node and io_range (as >> Bjorn mentioned)? > > I'm not quite sure I follow you here. Basically I think you want a generic "non-x86 PIO" framework that PCI just plugs into. > > I don't think that necessarily means you want to statically allocate regions of that PIO space to separate (pseudo-)devices. Instead, everyone shares that space and should be able to fail gracefully if some space is already occupied. > >> It would make sense. We would be somewhat decoupling PIO from PCI. > > Yes :). > >> I think that other architectures, like PPC, and other code would need to >> be fixed up to handle this. > > I think only PPC, Microblaze and ARM are using this. Grep for PCI_IOBASE. It's not that many. > >> We need to consider all the other challenges/obstacles to this. > > Well, getting our abstraction levels right to me sounds like it's worth the obstacles. > >> >>> >>>> --- >>>> include/asm-generic/io.h | 50 ++++++++++++++++ >>>> include/linux/extio.h | 85 +++++++++++++++++++++++++++ >>>> include/linux/io.h | 1 + >>>> lib/Kconfig | 8 +++ >>>> lib/Makefile | 2 + >>>> lib/extio.c | 147 >>>> +++++++++++++++++++++++++++++++++++++++++++++++ xc>> create mode >>>> 100644 include/linux/extio.h >>>> create mode 100644 lib/extio.c >>>> >> >> <snip> >> >>>> + * Copyright (C) 2016 Hisilicon Limited, All Rights Reserved. >>>> + * Author: Zhichang Yuan <yuanzhichang@xxxxxxxxxxxxx> >>>> + * >>>> + * This program is free software; you can redistribute it and/or modify >>>> + * it under the terms of the GNU General Public License version 2 as >>>> + * published by the Free Software Foundation. >>>> + * >>>> + * This program is distributed in the hope that it will be useful, >>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of >>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the >>>> + * GNU General Public License for more details. >>>> + * >>>> + * You should have received a copy of the GNU General Public License >>>> + * along with this program. If not, see >>>> <http://www.gnu.org/licenses/>. >>>> + */ >>>> + >>>> +#include <linux/io.h> >>>> +#include <linux/spinlock.h> >>>> + >>>> +static LIST_HEAD(extio_dev_list); >>>> +static DEFINE_RWLOCK(extio_list_lock); >>> >>> Why not just make the list an RCU list? Then you don't need read locks. >>> We also wouldn't create potential lock contention between devices that >>> could easily have parallel PIO operations (say a PCI device and an LPC >>> device). >>> >> >> OK >> >>>> + >>>> +void register_extio(struct extio_node *node) >>>> +{ >>>> + write_lock(&extio_list_lock); >>>> + list_add_tail(&node->list, &extio_dev_list); >>>> + write_unlock(&extio_list_lock); >>>> +} >>>> + >>>> +static struct extio_node *find_extio_token(unsigned long addr) >>>> +{ >>>> + struct extio_node *extio_entry; >>>> + >>>> + read_lock(&extio_list_lock); >>>> + list_for_each_entry(extio_entry, &extio_dev_list, list) { >>>> + if ((addr < extio_entry->io_start + extio_entry->range_size) && >>>> + (addr >= extio_entry->io_start)) >>>> + break; >>>> + } >>>> + read_unlock(&extio_list_lock); >>>> + return (&extio_entry->list == &extio_dev_list) ? NULL : >>>> extio_entry; >>>> +} >>>> + >>>> +struct extio_node *extio_find_node(struct fwnode_handle *node) >>>> +{ >>>> + struct extio_node *entry; >>>> + >>>> + read_lock(&extio_list_lock); >>>> + list_for_each_entry(entry, &extio_dev_list, list) { >>>> + if (entry->fwnode == node) >>>> + break; >>>> + } >>>> + read_unlock(&extio_list_lock); >>>> + >>>> + return (&entry->list == &extio_dev_list) ? NULL : entry; >>>> +} >>>> + >>>> +unsigned long extio_translate(struct fwnode_handle *node, >>>> + unsigned long bus_addr) >>>> +{ >>>> + struct extio_node *entry; >>>> + unsigned long port_id = -1; >>>> + >>>> + read_lock(&extio_list_lock); >>>> + list_for_each_entry(entry, &extio_dev_list, list) { >>>> + if (entry->fwnode == node && >>>> + bus_addr >= entry->bus_start && >>>> + bus_addr - entry->bus_start < entry->range_size) >>>> + port_id = entry->io_start + bus_addr - >>>> + entry->bus_start; >>>> + } >>>> + read_unlock(&extio_list_lock); >>>> + >>>> + return port_id; >>>> +} >>>> + >>>> +#ifdef PCI_IOBASE >>>> + >>>> +#define BUILD_EXTIO(bw, type) \ >>>> +type extio_in##bw(unsigned long addr) \ >>>> +{ \ >>>> + struct extio_node *extio_entry = find_extio_token(addr); \ >>>> + \ >>>> + if (!extio_entry) \ >>>> + return read##bw(PCI_IOBASE + addr); \ >>>> + return extio_entry->ops->pfin ? \ >>>> + extio_entry->ops->pfin(extio_entry->devpara, \ >>>> + addr, sizeof(type)) : -1; \ >>>> +} \ >>>> + \ >>>> +void extio_out##bw(type value, unsigned long addr) \ >>>> +{ \ >>>> + struct extio_node *extio_entry = find_extio_token(addr); \ >>>> + \ >>>> + if (!extio_entry) \ >>>> + write##bw(value, PCI_IOBASE + addr); \ >>> >>> All of the fallback code would also disappear as a nice side effect of >>> making pci pio handling a user of extio :). >> >> Is your idea that PCI IO space will also register accessors, which would >> be the same read{b,w,l}/write{b,w,l}? I am not so sure what is your ideas on this. Do you mean the snippet like these: #define BUILD_IO(bw, type) \ type extio_in##bw(unsigned long addr) \ { \ struct io_range *entry = find_io_range(addr); \ \ if (entry) \ return entry->ops->pfin(entry->devpara, \ addr, sizeof(type)); \ return read##bw(PCI_IOBASE + addr); \ } we add the last 'return read##bw(PCI_IOBASE + addr);' to keep the original logic of inX() in asm-generic/io.h; In above snippet, all the hosts applied extio should register their own ops->pfin(). Thanks, Zhichang > > Yes. If you need to later on accelerate that bit, you can always do something like > > if (extio_entry->ops->pfin == pci_extio_in) > return pci_extio_in(...); > > which should get you all the prefetcher and branch prediction benefits that the current version gives you. But for starters I'd leave that out, since I doubt it'll have measurable performance impact to go via an indirect function call. > >> >>> >> >> It would be nice to have a quicker way to so the lookup from address to >> node, as we loop all nodes in find_extio_token() every single time. > > You can always replace the search with a tree. But to me that's an implementation detail that's easy enough to replace in a follow-up patch series. > > > Alex > > . > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
