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SubjectRe: [PATCH v1 3/4] serial: 8250_pci: Always try MSI/MSI-X
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On 13. 07. 21, 12:40, Andy Shevchenko wrote:
> There is no need to try MSI/MSI-X only on selected devices.
> If MSI is not supported while neing advertised it means device

being

> is broken and we rather introduce a list of such devices which
> hopefully will be small or never appear.

Hmm, have you checked the commit which introduced the whitelist?

Nevertheless, this needs to handled with care: while many 8250 devices
actually claim to support MSI(-X) interrupts it should not be
enabled be
default. I had at least one device in my hands with broken MSI
implementation.

So better introduce a whitelist with devices that are known to support
MSI(-X) interrupts. I tested all devices mentioned in the patch.


You should have at least CCed the author for an input.

> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> drivers/tty/serial/8250/8250_pci.c | 28 ++++++++--------------------
> 1 file changed, 8 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
> index 937861327aca..02825c8c5f84 100644
> --- a/drivers/tty/serial/8250/8250_pci.c
> +++ b/drivers/tty/serial/8250/8250_pci.c
> @@ -58,18 +58,6 @@ struct serial_private {
>
> #define PCI_DEVICE_ID_HPE_PCI_SERIAL 0x37e
>
> -static const struct pci_device_id pci_use_msi[] = {
> - { PCI_DEVICE_SUB(PCI_VENDOR_ID_NETMOS, PCI_DEVICE_ID_NETMOS_9900,
> - 0xA000, 0x1000) },
> - { PCI_DEVICE_SUB(PCI_VENDOR_ID_NETMOS, PCI_DEVICE_ID_NETMOS_9912,
> - 0xA000, 0x1000) },
> - { PCI_DEVICE_SUB(PCI_VENDOR_ID_NETMOS, PCI_DEVICE_ID_NETMOS_9922,
> - 0xA000, 0x1000) },
> - { PCI_DEVICE_SUB(PCI_VENDOR_ID_HP_3PAR, PCI_DEVICE_ID_HPE_PCI_SERIAL,
> - PCI_ANY_ID, PCI_ANY_ID) },
> - { }
> -};
> -
> static int pci_default_setup(struct serial_private*,
> const struct pciserial_board*, struct uart_8250_port *, int);
>
> @@ -3994,14 +3982,9 @@ pciserial_init_ports(struct pci_dev *dev, const struct pciserial_board *board)
> if (board->flags & FL_NOIRQ) {
> uart.port.irq = 0;
> } else {
> - if (pci_match_id(pci_use_msi, dev)) {
> - dev_dbg(&dev->dev, "Using MSI(-X) interrupts\n");
> - pci_set_master(dev);
> - rc = pci_alloc_irq_vectors(dev, 1, 1, PCI_IRQ_ALL_TYPES);
> - } else {
> - dev_dbg(&dev->dev, "Using legacy interrupts\n");
> - rc = pci_alloc_irq_vectors(dev, 1, 1, PCI_IRQ_LEGACY);
> - }
> + pci_set_master(dev);

But bus mastering is not about MSIs. I *think* it's still OK, but you
need to document that in the commit log too.

Actually, why the commit which added this code turns on bus mastering?

> +
> + rc = pci_alloc_irq_vectors(dev, 1, 1, PCI_IRQ_ALL_TYPES);
> if (rc < 0) {
> kfree(priv);
> priv = ERR_PTR(rc);
> @@ -4009,6 +3992,11 @@ pciserial_init_ports(struct pci_dev *dev, const struct pciserial_board *board)
> }
>
> uart.port.irq = pci_irq_vector(dev, 0);
> +
> + if (pci_dev_msi_enabled(dev))
> + dev_dbg(&dev->dev, "Using MSI(-X) interrupts\n");
> + else
> + dev_dbg(&dev->dev, "Using legacy interrupts\n");
> }
>
> uart.port.dev = &dev->dev;
>

thanks,
--
js
suse labs

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