On Fri, Jul 16, 2021 at 4:07 PM Ralf Ramsauer
[off-list ref] wrote:

On 14/07/2021 15:35, Andy Shevchenko wrote:

quoted

On Wed, Jul 14, 2021 at 3:56 PM Ralf Ramsauer
[off-list ref] wrote:

quoted

On 14/07/2021 08:54, Jiri Slaby wrote:

quoted

On 13. 07. 21, 12:40, Andy Shevchenko wrote:

quoted

quoted

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.

Yep, back then I was testing three different 8250 pci cards. All of them
claimed to support MSI, while one really worked with MSI, the one that I
whitelisted. So I thought it would be better to use legacy IRQs as long
as no one tested a specific card to work with MSI.

Can you shed a light eventually what those cards are?

So I found a no-name el-cheapo card that has some issues with MSI:

Win Chip Head (WCH)

18:00.0 Serial controller: Device 1c00:3253 (rev 10) (prog-if 05 [16850])

The card comes with two serial lines. It comes perfectly up, if I enable
it to use MSI in the whitelist:

serial 0000:18:00.0: Using MSI(-X) interrupts
serial 0000:18:00.0: Setup PCI port: port 40c0, irq 104, type 0
0000:18:00.0: ttyS6 at I/O 0x40c0 (irq = 104, base_baud = 115200) is a
XR16850
serial 0000:18:00.0: Setup PCI port: port 40c8, irq 104, type 0
0000:18:00.0: ttyS7 at I/O 0x40c8 (irq = 104, base_baud = 115200) is a
XR16850

After loading 8250_pci, lspci -vvs 18:0.0 tells:

        Capabilities: [68] MSI: Enable+ Count=1/32 Maskable+ 64bit+
                Address: 00000000fee000b8  Data: 0000
                Masking: ffffffff  Pending: 00000000

Looks good so far. Now let's echo to the device.

$ echo asdf > /dev/ttyS6

-- stuck. The echoing process stucks at close():

write(1, "asdf\n", 5)                   = 5
close(1

Stuck in the sense of: the echo is still killable, no crashes. The same
happens if I try to access the device with stty. So something is odd
here. However, the Netmos cards that I whitelisted do a great job.

Can you share somehow the `lspci -vvv -xx -nk; lspci -t` with and
without MSI enabled? (I want to understand what is going on with it)

So I can't tell if I was just unlucky to grab a card that has issues
with MSI, and this is an exception rather than the rule…

-- 
With Best Regards,
Andy Shevchenko