Re: [Article] NuttX on Star64 JH7110: RISC-V PLIC Interrupts and Serial I/O
Congratulations Lup! I'm looking forward to see Star64 JH7110 integrated into mainline. BR, Alan On 8/2/23, Lee, Lup Yuen wrote: > Thanks Tomek! Here's the backup link for the article (since Codeberg is > down): https://lupyuen.github.io/articles/plic > > I found out (from Hacker News) that JH7110 uses a Synopsys DesignWare 8250 > UART that has a peculiar problem with the Line Control Register (LCR)... If > we write to LCR while the UART is busy, it will trigger spurious UART > Interrupts. > > The fix is to wait for the UART to be not busy before writing to LCR. > Here's my proposed patch for the NuttX 16550 UART Driver > (drivers/serial/uart_16550.c): > https://github.com/lupyuen2/wip-pinephone-nuttx/pull/36/files#diff-f208234edbfb636de240a0fef1c85f9cecb37876d5bc91ffb759f70a1e96b1d1 > > We're all ready to merge NuttX for JH7110! :-) > > Lup > > On Wed, Aug 2, 2023 at 7:19 AM Tomek CEDRO wrote: > >> On Wed, Aug 2, 2023 at 1:14 AM Lee, Lup Yuen wrote: >> > NuttX on Star64 JH7110 RISC-V SBC is almost ready! But we're stuck with >> > 16550 UART Controller firing too many Spurious Interrupts. >> >> Good luck Lup! IRQ storm is (was?) known problem on a desktop machines >> too! I hope you fight that beast soon :-) :-) >> >> -- >> CeDeROM, SQ7MHZ, http://www.tomek.cedro.info >> >
Re: [Article] NuttX on Star64 JH7110: RISC-V PLIC Interrupts and Serial I/O
Thanks Tomek! Here's the backup link for the article (since Codeberg is down): https://lupyuen.github.io/articles/plic I found out (from Hacker News) that JH7110 uses a Synopsys DesignWare 8250 UART that has a peculiar problem with the Line Control Register (LCR)... If we write to LCR while the UART is busy, it will trigger spurious UART Interrupts. The fix is to wait for the UART to be not busy before writing to LCR. Here's my proposed patch for the NuttX 16550 UART Driver (drivers/serial/uart_16550.c): https://github.com/lupyuen2/wip-pinephone-nuttx/pull/36/files#diff-f208234edbfb636de240a0fef1c85f9cecb37876d5bc91ffb759f70a1e96b1d1 We're all ready to merge NuttX for JH7110! :-) Lup On Wed, Aug 2, 2023 at 7:19 AM Tomek CEDRO wrote: > On Wed, Aug 2, 2023 at 1:14 AM Lee, Lup Yuen wrote: > > NuttX on Star64 JH7110 RISC-V SBC is almost ready! But we're stuck with > > 16550 UART Controller firing too many Spurious Interrupts. > > Good luck Lup! IRQ storm is (was?) known problem on a desktop machines > too! I hope you fight that beast soon :-) :-) > > -- > CeDeROM, SQ7MHZ, http://www.tomek.cedro.info >
Re: [Article] NuttX on Star64 JH7110: RISC-V PLIC Interrupts and Serial I/O
On Wed, Aug 2, 2023 at 1:14 AM Lee, Lup Yuen wrote: > NuttX on Star64 JH7110 RISC-V SBC is almost ready! But we're stuck with > 16550 UART Controller firing too many Spurious Interrupts. Good luck Lup! IRQ storm is (was?) known problem on a desktop machines too! I hope you fight that beast soon :-) :-) -- CeDeROM, SQ7MHZ, http://www.tomek.cedro.info
[Article] NuttX on Star64 JH7110: RISC-V PLIC Interrupts and Serial I/O
NuttX on Star64 JH7110 RISC-V SBC is almost ready! But we're stuck with 16550 UART Controller firing too many Spurious Interrupts. In this article, we explain… (1) Why there’s No Console Output from NuttX Apps (2) How Serial I/O works in NuttX QEMU (3) How UART I/O differs for Star64 vs QEMU (4) What’s the RISC-V Platform-Level Interrupt Controller (PLIC) (5) Why we delegate RISC-V Machine-Mode Interrupts to Supervisor-Mode (6) How NuttX Star64 handles UART Interrupts (7) Which leads to a new problem: 16550 UART Controller fires too many Spurious Interrupts! Check out the article: https://lupyuen.codeberg.page/articles/plic.html Lup
