22.11.2021 15:44, Patrik John пишет: > The current implementation uses 0 as lower limit for the baud rate tolerance which contradicts the initial commit description (https://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux.git/commit/drivers/tty/serial/serial-tegra.c?h=for-next&id=d781ec21bae6ff8f9e07682e8947a654484611f5) of +4/-4% tolerance for older tegra chips other than Tegra186 and Tegra194. > This causes issues on UART initilization as soon as the actual baud rate clock is slightly lower than required which we have seen on the Tegra124-based Toradex Apalis TK1 which also uses tegra30-hsuart as compatible in the DT serial node (for reference line 1540ff https://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux.git/tree/arch/arm/boot/dts/tegra124-apalis-v1.2.dtsi?h=for-next) > > The standard baud rate tolerance limits are also stated in the tegra20-hsuart driver description (https://www.kernel.org/doc/Documentation/devicetree/bindings/serial/nvidia%2Ctegra20-hsuart.txt). > > The previously introduced check_rate_in_range() always fails due to the lower limit set to 0 even if the actual baud rate is within the required -4% tolerance. > > static int tegra_check_rate_in_range(struct tegra_uart_port *tup) > { > long diff; > diff = ((long)(tup->configured_rate - tup->required_rate) * 10000) > / tup->required_rate; > if (diff < (tup->cdata->error_tolerance_low_range * 100) || > diff > (tup->cdata->error_tolerance_high_range * 100)) { > dev_err(tup->uport.dev, > "configured baud rate is out of range by %ld", diff); > return -EIO; > } > return 0; > } > > Changing the lower tolerance limit to the actual -4% resolved the issues for the Tegra124 and should resolve potential issues for other Tegra20/Tegra30 based platforms as well. Hi, 1. The text of commit message should be wrapped around 75 chars. Please run "./scripts/checkpatch.pl example.patch" and fix all reported problems before sending out the patch. 2. This patch should have v2 in the title. Please use the "git format-patch -v3" next time, it will generate patch with v3 in the title. 3. Use "Link" tag and put all http links here, before the Signed-off-by tag, like this: Link: https://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux.git/commit/drivers/tty/serial/serial-tegra.c?h=for-next&id=d781ec21bae6ff8f9e07682e8947a654484611f5 Link: https://git.kernel.org/pub/scm/linux/kernel/git/tegra/linux.git/tree/arch/arm/boot/dts/tegra124-apalis-v1.2.dtsi?h=for-next Link: https://www.kernel.org/doc/Documentation/devicetree/bindings/serial/nvidia%2Ctegra20-hsuart.txt > Signed-off-by: Patrik John <patrik.john@xxxxxxxxxx> > --- > 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, > }; > >
