On Mon, Nov 22, 2021 at 01:44:26PM +0100, Patrik John wrote: > 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) All of these links will break in a few days. And a line number is not "1540ff" :( > > 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). You can just reference a file in the kernel source tree directly, no need to go back to kernel.org > > 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. Can you please wrap your changelog text at 72 columns like git asked you to when you committed the change to your local tree? > > 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; > } I do not understand, why is this code in the changelog? > > 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. > > Signed-off-by: Patrik John <patrik.john@xxxxxxxxxx> What commit does this fix? Should it have a "Fixes:" tag in it? And should it go to stable kernel(s)? Also, this is a v2 patch, please include below the --- line what changed from the previous version when you resend v3. thanks, greg k-h
