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Diffstat (limited to 'target/linux/tegra/patches-5.4/100-serial8250-on-tegra-hsuart-recover-from-spurious-interrupts-due-to-tegra2-silicon-bug.patch')
-rw-r--r--target/linux/tegra/patches-5.4/100-serial8250-on-tegra-hsuart-recover-from-spurious-interrupts-due-to-tegra2-silicon-bug.patch77
1 files changed, 0 insertions, 77 deletions
diff --git a/target/linux/tegra/patches-5.4/100-serial8250-on-tegra-hsuart-recover-from-spurious-interrupts-due-to-tegra2-silicon-bug.patch b/target/linux/tegra/patches-5.4/100-serial8250-on-tegra-hsuart-recover-from-spurious-interrupts-due-to-tegra2-silicon-bug.patch
deleted file mode 100644
index 08ed9d441c..0000000000
--- a/target/linux/tegra/patches-5.4/100-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
-@@ -133,6 +133,38 @@ static irqreturn_t serial8250_interrupt(
-
- if (l == i->head && pass_counter++ > PASS_LIMIT)
- 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);