serial: tegra: Change lower tolerance baud rate limit for tegra20 and tegra30

BugLink: https://bugs.launchpad.net/bugs/1953731
commit b40de7469ef135161c80af0e8c462298cc5dac00 upstream.

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>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index 45e2e4109acd0d8a3557b379674bb2726a95310c..b6223fab0687da64f947e70f20b72b6b419590ff 100644 (file)
--- 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,
 };