From f22dd43fc16671c7c1237e855dfb65b5f73cc0eb Mon Sep 17 00:00:00 2001 From: Johan Hovold Date: Wed, 21 Apr 2021 11:54:45 +0200 Subject: [PATCH] serial: altera_jtaguart: drop low-latency workaround Commit 53dd0ba7a6f4 ("tty: serial: altera_jtag: drop uart_port->lock before calling tty_flip_buffer_push()") claimed to address a locking issue but only provided a dubious lockdep splat from an unrelated driver, which in the end turned out to be due a broken local change carried by the author. Unfortunately these patches were merged before the issue had been analysed properly so the commit messages makes no sense whatsoever. The real issue was first seen on RT which at the time effectively always set the low_latency flag for all serial drivers by patching tty_flip_buffer_push(). This in turn revealed that many drivers did not handle the infamous low_latency behaviour which meant that data was pushed immediately to the line discipline instead of being deferred to a work queue. Since commit a9c3f68f3cd8 ("tty: Fix low_latency BUG"), tty_flip_buffer_push() always schedules a work item to push data to the line discipline and there's no need to keep any low_latency hacks around. Link: https://lore.kernel.org/linux-serial/cover.1376923198.git.viresh.kumar@linaro.org/ Cc: Tobias Klauser Acked-by: Tobias Klauser Signed-off-by: Johan Hovold Link: https://lore.kernel.org/r/20210421095509.3024-3-johan@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/altera_jtaguart.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/tty/serial/altera_jtaguart.c b/drivers/tty/serial/altera_jtaguart.c index d0ca9cf29b62..23c4e0e79694 100644 --- a/drivers/tty/serial/altera_jtaguart.c +++ b/drivers/tty/serial/altera_jtaguart.c @@ -131,9 +131,7 @@ static void altera_jtaguart_rx_chars(struct altera_jtaguart *pp) uart_insert_char(port, 0, 0, ch, flag); } - spin_unlock(&port->lock); tty_flip_buffer_push(&port->state->port); - spin_lock(&port->lock); } static void altera_jtaguart_tx_chars(struct altera_jtaguart *pp)