On 16/07/2021 17:01, Andy Shevchenko wrote: > On Fri, Jul 16, 2021 at 4:07 PM Ralf Ramsauer > wrote: >> On 14/07/2021 15:35, Andy Shevchenko wrote: >>> On Wed, Jul 14, 2021 at 3:56 PM Ralf Ramsauer >>> wrote: >>>> On 14/07/2021 08:54, Jiri Slaby wrote: >>>>> On 13. 07. 21, 12:40, Andy Shevchenko wrote: >>> >>>>> 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) Sure, please find it attached. Ralf > >> 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… >