From b40de7469ef135161c80af0e8c462298cc5dac00 Mon Sep 17 00:00:00 2001
From: Patrik John <patrik.john@u-blox.com>
Date: Tue, 23 Nov 2021 14:27:38 +0100
Subject: [PATCH] serial: tegra: Change lower tolerance baud rate limit for tegra20 and tegra30
Git-commit: b40de7469ef135161c80af0e8c462298cc5dac00
Patch-mainline: v5.16-rc4
References: git-fixes

The current implementation uses 0 as lower limit for the baud rate
tolerance for tegra20 and tegra30 chips which causes isses on UART
initialization as soon as baud rate clock is lower than required even
when within the standard UART tolerance of +/- 4%.

This fix aligns the implementation with the initial commit description
of +/- 4% tolerance for tegra chips other than tegra186 and
tegra194.

Fixes: d781ec21bae6 ("serial: tegra: report clk rate errors")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Patrik John <patrik.john@u-blox.com>
Link: https://lore.kernel.org/r/sig.19614244f8.20211123132737.88341-1-patrik.john@u-blox.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/tty/serial/serial-tegra.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index 45e2e4109acd..b6223fab0687 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -1506,7 +1506,7 @@ static struct tegra_uart_chip_data tegra20_uart_chip_data = {
 	.fifo_mode_enable_status	= false,
 	.uart_max_port			= 5,
 	.max_dma_burst_bytes		= 4,
-	.error_tolerance_low_range	= 0,
+	.error_tolerance_low_range	= -4,
 	.error_tolerance_high_range	= 4,
 };
 
@@ -1517,7 +1517,7 @@ static struct tegra_uart_chip_data tegra30_uart_chip_data = {
 	.fifo_mode_enable_status	= false,
 	.uart_max_port			= 5,
 	.max_dma_burst_bytes		= 4,
-	.error_tolerance_low_range	= 0,
+	.error_tolerance_low_range	= -4,
 	.error_tolerance_high_range	= 4,
 };
 
-- 
2.31.1