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<p class="MsoNormal"><span style="font-family:Consolas">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">I have come across the following problem:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">Error:<br>
After pasting ~130kb text in console, multiple “ismt_smbus 0000:00:12.0: completion wait timed out” messages are seen in dmesg.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">Configuration:<br>
1. Custom Debian-based operating system based on Linux kernel 6.1.25-13-amd64.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">2. Sysrq is set to 16.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">3. Following peripherals are present:<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span style="font-family:Consolas">a. Intel Corporation Atom Processor C3000 Series SMBus Contoller (Driver i2c_ismt).<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span style="font-family:Consolas">b. Serial controller: Intel Corporation Atom Processor C3000 Series HSUART Controller (Driver 8250_mid)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">4. The original baudrate of the serial controller is 115200, however, we configure its baudrate to 57600.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">5. Model name: Intel(R) Atom(TM) CPU C3558 @ 2.20GHz; Number of cores = 4; RAM = 16GB.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">Additional observations:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">1. The paste operation takes around 61 minutes.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">2. Number of interrupts on serial controller during this time is around 175000.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">3. Number of interrupts on SMBus controller during this time is around 346000.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">4. When sysrq is set to 0, the problem does not occur.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">5. The interrupts on the IRQ lines for serial driver and SMBus driver are serviced by the same core.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">6. If I ensure that the interrupts on the serial and SMBus driver are managed by different cores, the problem does not occur.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">7. During the paste process, the CPU usage of the core (that handles both interrupts) goes to 100%, then suddenly drops to 0%, before returning to normal values (around 90%).<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">8. If the baudrate is set to 115200 (original value), the problem does not occur.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">I studied the source code for the serial driver. I could not find anything which may have caused other interrupts to get blocked.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">I would appreciate any direction and/or explanation for this behavior. Please let me know if any additional information is needed from my end.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas">Rahul<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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