From: Bjorn Helgaas <helgaas@kernel.org>
To: Huacai Chen <chenhuacai@loongson.cn>
Cc: "Bjorn Helgaas" <bhelgaas@google.com>,
"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
"Rob Herring" <robh@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
linux-pci@vger.kernel.org, "Xuefeng Li" <lixuefeng@loongson.cn>,
"Huacai Chen" <chenhuacai@gmail.com>,
"Jiaxun Yang" <jiaxun.yang@flygoat.com>
Subject: Re: [PATCH V13 3/6] PCI: loongson: Don't access unexisting devices
Date: Tue, 31 May 2022 18:14:07 -0500 [thread overview]
Message-ID: <20220531231407.GA795410@bhelgaas> (raw)
In-Reply-To: <20220430084846.3127041-4-chenhuacai@loongson.cn>
On Sat, Apr 30, 2022 at 04:48:43PM +0800, Huacai Chen wrote:
> On LS2K/LS7A, some unexisting devices don't return 0xffffffff when
> scanning. This is a hardware flaw but we can only avoid it by software
> now.
s/unexisting/non-existant/ (many occurrences: subject line, commit
log, comments below)
What happens in other situations that normally cause Unsupported
Request or similar errors? For example, memory reads/writes to a
device in D3hot should cause an Unsupported Request error. I'm
wondering whether other error handling assumptions might be broken
on LS2K/LS7A.
> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
> ---
> drivers/pci/controller/pci-loongson.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
> index adbfa4a2330f..48316daa1f23 100644
> --- a/drivers/pci/controller/pci-loongson.c
> +++ b/drivers/pci/controller/pci-loongson.c
> @@ -138,6 +138,8 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
> int where)
> {
> unsigned char busnum = bus->number;
> + unsigned int device = PCI_SLOT(devfn);
> + unsigned int function = PCI_FUNC(devfn);
> struct loongson_pci *priv = pci_bus_to_loongson_pci(bus);
>
> if (pci_is_root_bus(bus))
> @@ -147,8 +149,13 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
> * Do not read more than one device on the bus other than
> * the host bus. For our hardware the root bus is always bus 0.
> */
> - if (priv->data->flags & FLAG_DEV_FIX &&
> - !pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
> + if ((priv->data->flags & FLAG_DEV_FIX) && bus->self) {
> + if (!pci_is_root_bus(bus) && (device > 0))
> + return NULL;
> + }
> +
> + /* Don't access unexisting devices */
> + if (pci_is_root_bus(bus) && (device >= 9 && device <= 20 && function > 0))
Yuck. This is pretty nasty magic. If this is something that might be
fixed in future versions of the hardware, maybe you should factor this
out into a function pointer in loongson_pci_data or something.
> return NULL;
>
> /* CFG0 can only access standard space */
> --
> 2.27.0
>
next prev parent reply other threads:[~2022-05-31 23:14 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-30 8:48 [PATCH V13 0/6] PCI: Loongson pci improvements and quirks Huacai Chen
2022-04-30 8:48 ` [PATCH V13 1/6] PCI: loongson: Use generic 8/16/32-bit config ops on LS2K/LS7A Huacai Chen
2022-06-01 2:08 ` Bjorn Helgaas
2022-06-02 4:18 ` Huacai Chen
2022-04-30 8:48 ` [PATCH V13 2/6] PCI: loongson: Add ACPI init support Huacai Chen
2022-05-31 23:04 ` Bjorn Helgaas
2022-06-02 7:09 ` Huacai Chen
2022-04-30 8:48 ` [PATCH V13 3/6] PCI: loongson: Don't access unexisting devices Huacai Chen
2022-05-31 23:14 ` Bjorn Helgaas [this message]
2022-06-02 4:28 ` Huacai Chen
2022-06-02 16:23 ` Bjorn Helgaas
2022-06-02 20:00 ` Jiaxun Yang
2022-04-30 8:48 ` [PATCH V13 4/6] PCI: loongson: Improve the MRRS quirk for LS7A Huacai Chen
2022-06-01 2:22 ` Bjorn Helgaas
2022-06-01 11:59 ` Jiaxun Yang
2022-06-02 4:17 ` Huacai Chen
2022-06-02 16:20 ` Bjorn Helgaas
2022-06-03 12:13 ` Krzysztof Hałasa
2022-06-03 22:57 ` Jiaxun Yang
2022-06-04 0:07 ` Bjorn Helgaas
2022-06-08 8:29 ` Huacai Chen
2022-04-30 8:48 ` [PATCH V13 5/6] PCI: Add quirk for LS7A to avoid reboot failure Huacai Chen
2022-05-31 23:35 ` Bjorn Helgaas
2022-06-02 12:48 ` Huacai Chen
2022-06-02 16:29 ` Bjorn Helgaas
2022-06-08 9:34 ` Huacai Chen
2022-06-08 19:31 ` Bjorn Helgaas
2022-06-16 8:39 ` Huacai Chen
2022-06-16 22:57 ` Bjorn Helgaas
2022-06-17 2:21 ` Huacai Chen
2022-06-17 11:37 ` Bjorn Helgaas
2022-06-17 12:14 ` Huacai Chen
2022-04-30 8:48 ` [PATCH V13 6/6] PCI: Add quirk for multifunction devices of LS7A Huacai Chen
2022-06-01 2:07 ` Bjorn Helgaas
2022-06-01 7:36 ` Jianmin Lv
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