diff options
Diffstat (limited to 'target/linux/tegra/patches-4.19/100-serial8250-on-tegra-hsuart-recover-from-spurious-interrupts-due-to-tegra2-silicon-bug.patch')
| -rw-r--r-- | target/linux/tegra/patches-4.19/100-serial8250-on-tegra-hsuart-recover-from-spurious-interrupts-due-to-tegra2-silicon-bug.patch | 77 |
1 files changed, 0 insertions, 77 deletions
diff --git a/target/linux/tegra/patches-4.19/100-serial8250-on-tegra-hsuart-recover-from-spurious-interrupts-due-to-tegra2-silicon-bug.patch b/target/linux/tegra/patches-4.19/100-serial8250-on-tegra-hsuart-recover-from-spurious-interrupts-due-to-tegra2-silicon-bug.patch deleted file mode 100644 index 9e8c331934..0000000000 --- a/target/linux/tegra/patches-4.19/100-serial8250-on-tegra-hsuart-recover-from-spurious-interrupts-due-to-tegra2-silicon-bug.patch +++ /dev/null @@ -1,77 +0,0 @@ -From patchwork Fri Jul 13 11:32:42 2018 -Content-Type: text/plain; charset="utf-8" -MIME-Version: 1.0 -Content-Transfer-Encoding: 7bit -Subject: serial8250 on tegra hsuart: recover from spurious interrupts due to - tegra2 silicon bug -X-Patchwork-Submitter: "David R. Piegdon" <lkml@p23q.org> -X-Patchwork-Id: 943440 -Message-Id: <4676ea34-69ce-5422-1ded-94218b89f7d9@p23q.org> -To: linux-tegra@vger.kernel.org -Date: Fri, 13 Jul 2018 11:32:42 +0000 -From: "David R. Piegdon" <lkml@p23q.org> -List-Id: <linux-tegra.vger.kernel.org> - -Hi, -a while back I sent a few mails regarding spurious interrupts in the -UARTA (hsuart) block of the Tegra2 SoC, when using the 8250 driver for -it instead of the hsuart driver. After going down a pretty deep -debugging/testing hole, I think I found a patch that fixes the issue. So -far testing in a reboot-cycle suggests that the error frequency dropped -from >3% of all reboots to at least <0.05% of all reboots. Tests -continue to run over the weekend. - -The patch below already is a second iteration; the first did not reset -the MCR or contain the lines below '// clear interrupts'. This resulted -in no more spurious interrupts, but in a few % of spurious interrupts -that were recovered the UART block did not receive any characters any -more. So further resetting was required to fully reacquire operational -state of the UART block. - -I'd love any comments/suggestions on this! - -Cheers, - -David - ---- a/drivers/tty/serial/8250/8250_core.c -+++ b/drivers/tty/serial/8250/8250_core.c -@@ -136,6 +136,38 @@ static irqreturn_t serial8250_interrupt( - "serial8250: too much work for irq%d\n", irq); - break; - } -+ -+#ifdef CONFIG_ARCH_TEGRA_2x_SOC -+ if (!handled && (port->type == PORT_TEGRA)) { -+ /* -+ * Fix Tegra 2 CPU silicon bug where sometimes -+ * "TX holding register empty" interrupts result in a -+ * bad (metastable?) state in Tegras HSUART IP core. -+ * Only way to recover seems to be to reset all -+ * interrupts as well as the TX queue and the MCR. -+ * But we don't want to loose any outgoing characters, -+ * so only do it if the RX and TX queues are empty. -+ */ -+ unsigned char lsr = port->serial_in(port, UART_LSR); -+ const unsigned char fifo_empty_mask = -+ (UART_LSR_TEMT | UART_LSR_THRE); -+ if (((lsr & (UART_LSR_DR | fifo_empty_mask)) == -+ fifo_empty_mask)) { -+ port->serial_out(port, UART_IER, 0); -+ port->serial_out(port, UART_MCR, 0); -+ serial8250_clear_and_reinit_fifos(up); -+ port->serial_out(port, UART_MCR, up->mcr); -+ port->serial_out(port, UART_IER, up->ier); -+ // clear interrupts -+ serial_port_in(port, UART_LSR); -+ serial_port_in(port, UART_RX); -+ serial_port_in(port, UART_IIR); -+ serial_port_in(port, UART_MSR); -+ up->lsr_saved_flags = 0; -+ up->msr_saved_flags = 0; -+ } -+ } -+#endif - } while (l != end); - - spin_unlock(&i->lock); |