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Date: Thu, 15 Jul 2021 09:07:31 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Paul Menzel <pmenzel@...gen.mpg.de>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Guohan Lu <lguohan@...il.com>,
Billie Alsup <balsup@...co.com>,
Madhava Reddy Siddareddygari <msiddare@...co.com>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
Sergey Miroshnichenko <s.miroshnichenko@...ro.com>
Subject: Re: [RFC][PATCH] PCI: Reserve address space for powered-off devices
behind PCIe bridges
[+cc Sergey]
On Thu, Jul 15, 2021 at 03:50:49PM +0200, Paul Menzel wrote:
> [Add Billie’s correct address.]
>
> Am 13.07.21 um 09:31 schrieb Paul Menzel:
> > From: balsup <balsup@...toso.com>
>
> Billie Alsup <balsup@...co.com>
>
> > Data path devices are powered off by default, they will not be visible at
> > BIOS stage and memory for these devices is not reserved.
> >
> > By default, no address space would be reserved on the bridges for these
> > unpowered devices. When they were powered up, they could fail to initialize
> > because there was no appropriately aligned window available for a given
> > BAR.
> >
> > This patch will reserve address space for data path devices that are behind
> > PCIe bridge, so that when devices are available PCIe subsystem will be
> > assign the address within the specified range.
> >
> > Signed-off-by: Madhava Reddy Siddareddygari <msiddare@...co.com>
> > ---
> > This patch was submitted to the SONiC project for a Cisco device [1].
> > It’s better to have it reviewed and committed upstream though.
> >
> > drivers/pci/setup-bus.c | 159 ++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 159 insertions(+)
> >
> > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > index 2ce636937c6e..266097984e19 100644
> > --- a/drivers/pci/setup-bus.c
> > +++ b/drivers/pci/setup-bus.c
> > @@ -967,6 +967,148 @@ static inline resource_size_t calculate_mem_align(resource_size_t *aligns,
> > return min_align;
> > }
> > +#define PLX_RES_MAGIC_VALUE 0xABBA
> > +#define PLX_RES_DS_PORT_REG0 0xC6C
> > +#define PLX_RES_DS_PORT_REG1 0xC70
> > +#define PLX_RES_MAGIC_OFFSET 0xC76
> > +#define PLX_RES_NP_MASK 0x1
> > +#define PLX_RES_P_MASK 0x1F
> > +
> > +static struct pci_dev *
> > +plx_find_nt_device(struct pci_bus *bus, unsigned short brg_dev_id)
> > +{
> > + struct pci_dev *dev, *nt_virt_dev = NULL;
> > + struct pci_bus *child_bus;
> > + unsigned short vendor, devid, class;
> > +
> > + if (!bus)
> > + return NULL;
> > +
> > + list_for_each_entry(child_bus, &bus->children, node) {
> > + list_for_each_entry(dev, &child_bus->devices, bus_list) {
> > + vendor = dev->vendor;
> > + devid = dev->device;
> > + class = dev->class >> 8;
> > +
> > + if ((vendor == PCI_VENDOR_ID_PLX) &&
> > + (brg_dev_id == devid) &&
> > + (class == PCI_CLASS_BRIDGE_OTHER)) {
> > + dev_dbg(&dev->dev, "Found NT device 0x%x\n",
> > + devid);
> > + nt_virt_dev = dev;
> > + break;
> > + }
> > + }
> > +
> > + if (nt_virt_dev)
> > + break;
> > + }
> > + return nt_virt_dev;
> > +}
> > +
> > +static resource_size_t
> > +pci_get_plx_downstream_res_size(struct pci_bus *bus, unsigned long res_type)
> > +{
> > + int depth = 0;
> > + resource_size_t size = 0;
> > + struct pci_dev *dev = bus->self;
> > + struct pci_bus *tmp_bus;
> > + struct pci_dev *nt_virt_dev;
> > + u16 res_magic = 0;
> > +
> > + /*
> > + * 32 bits to store the memory requirement for PLX ports.
> > + * Following is the layout:
> > + * np32_0:1; --> non-prefetchable port 0
> > + * p64_0:5; --> prefetchable port 0
> > + * np32_1:1; --> non-prefetchable port 1
> > + * p64_1:5; --> prefetchable port 1
> > + * np32_2:1; --> non-prefetchable port 2
> > + * p64_2:5; --> prefetchable port 2
> > + * np32_3:1; --> non-prefetchable port 3
> > + * p64_3:5; --> prefetchable port 3
> > + * np32_4:1; --> non-prefetchable port 4
> > + * p64_4:5; --> prefetchable port 4
> > + * reserved:2;
> > + */
> > + unsigned int port_bitmap;
> > +
> > + u32 mem_res_bitmap = 0;
> > + unsigned int ds_port_offset = 0;
> > + unsigned short multiplier = 0;
> > + unsigned short np_size = 0;
> > +
> > + /*
> > + * PLX8713 used on FC4 and FC8
> > + * PLX8725 used on FC12 and FC18
> > + */
> > + if (!dev || dev->vendor != PCI_VENDOR_ID_PLX ||
> > + ((dev->device & 0xFF00) != 0x8700))
> > + return size;
> > +
> > + tmp_bus = bus;
> > + while (tmp_bus->parent) {
> > + tmp_bus = tmp_bus->parent;
> > + depth++;
> > + }
> > +
> > + /* Only for Second level bridges */
> > + if (depth != 5)
> > + return size;
> > +
> > + nt_virt_dev = plx_find_nt_device(bus->parent, 0x87b0);
> > + if (nt_virt_dev) {
> > + pci_read_config_word(nt_virt_dev, PLX_RES_MAGIC_OFFSET,
> > + &res_magic);
> > + dev_dbg(&nt_virt_dev->dev,
> > + "Magic offset of 0x%x found in NT device\n", res_magic);
> > + }
> > +
> > + if (res_magic == PLX_RES_MAGIC_VALUE) {
> > + /*
> > + * The pacifics are connected on PLX ports:
> > + * FC4 and FC8: #3, #4
> > + * FC12 : #3, #4, #5
> > + * FC18 : #3, #4, #5, #11
> > + */
> > +
> > + /* Calculate resource based on EEPROM values */
> > + ds_port_offset = (bus->number - bus->parent->number) - 1;
> > + if (ds_port_offset < 5) {
> > + pci_read_config_dword(nt_virt_dev, PLX_RES_DS_PORT_REG0,
> > + &mem_res_bitmap);
> > + } else {
> > + ds_port_offset -= 5;
> > + pci_read_config_dword(nt_virt_dev, PLX_RES_DS_PORT_REG1,
> > + &mem_res_bitmap);
> > + }
> > + port_bitmap = mem_res_bitmap;
> > + dev_dbg(&bus->dev, "Port offset: 0x%x, res bitmap 0x%x\n",
> > + ds_port_offset, mem_res_bitmap);
> > +
> > + if (ds_port_offset < 5) {
> > + u8 m[] = { 26, 20, 14, 8, 2 };
> > + u8 s[] = { 31, 25, 19, 13, 7 };
> > +
> > + multiplier = (port_bitmap >> m[ds_port_offset]) & PLX_RES_P_MASK;
> > + np_size = (port_bitmap >> s[ds_port_offset]) & PLX_RES_NP_MASK;
> > +
> > + dev_dbg(&bus->dev, "Multiplier: %d, np_size: %d\n",
> > + multiplier, np_size);
> > +
> > + if (res_type & IORESOURCE_PREFETCH) {
> > + size = 0x100000 << (multiplier - 1);
> > + dev_dbg(&bus->dev, "Pref Multiplier %d, Size 0x%llx\n",
> > + multiplier, (long long) size);
> > + } else if (np_size) {
> > + size = 0x100000;
> > + dev_dbg(&bus->dev, "NP Size 0x%llx\n", (long long) size);
> > + }
> > + }
> > + }
> > + return size;
> > +}
> > +
> > /**
> > * pbus_size_mem() - Size the memory window of a given bus
> > *
> > @@ -1001,6 +1143,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> > resource_size_t children_add_size = 0;
> > resource_size_t children_add_align = 0;
> > resource_size_t add_align = 0;
> > + unsigned int dev_count = 0;
> > if (!b_res)
> > return -ENOSPC;
> > @@ -1016,6 +1159,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> > list_for_each_entry(dev, &bus->devices, bus_list) {
> > int i;
> > + dev_count++;
> > for (i = 0; i < PCI_NUM_RESOURCES; i++) {
> > struct resource *r = &dev->resource[i];
> > resource_size_t r_size;
> > @@ -1071,6 +1215,21 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask,
> > }
> > }
> > + /* Static allocation for FC pacific */
> > + if (!size && !dev_count) {
> > + size = pci_get_plx_downstream_res_size(bus, type);
> > + if (size) {
> > + order = __ffs(size);
> > + dev_dbg(&bus->self->dev, "order for %llx is %u\n", (long long) size, order);
> > + if ((order >= 20) &&
> > + ((order -= 20) < ARRAY_SIZE(aligns)) &&
> > + (order > max_order)) {
> > + max_order = order;
> > + dev_dbg(&bus->self->dev, "max_order reset to %d; size %zx\n", max_order, (size_t)size);
> > + }
> > + }
> > + }
> > +
> > min_align = calculate_mem_align(aligns, max_order);
> > min_align = max(min_align, window_alignment(bus, b_res->flags));
> > size0 = calculate_memsize(size, min_size, 0, 0, resource_size(b_res), min_align);
>
> This is basically a request for comments, how to deal with such
> hardware, which is going to run Linux based network operating
> systems (NOS) like SONiC.
I don't think this patch is practical for upstream as-is because it
inserts so much device-specific stuff in generic code. That won't
scale when we try to extend it for other similar devices.
I think the long-term solution is something like Sergey's work on
movable BARs [1], but that needs testing and review and hasn't been
merged yet.
In the short term, you might be able to work around this with the
"pci=resource_alignment=" or "pci=hpmmiosize=" kernel parameters.
[1] https://lore.kernel.org/linux-pci/20191024171228.877974-1-s.miroshnichenko@yadro.com/
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