From 09864c1cdf5c537bd01bff45181406e422ea988c Mon Sep 17 00:00:00 2001 From: Stefan-gabriel Mirea Date: Fri, 9 Aug 2019 11:29:16 +0000 Subject: tty: serial: Add linflexuart driver for S32V234 Introduce support for LINFlex driver, based on: - the version of Freescale LPUART driver after commit b3e3bf2ef2c7 ("Merge 4.0-rc7 into tty-next"); - commit abf1e0a98083 ("tty: serial: fsl_lpuart: lock port on console write"). In this basic version, the driver can be tested using initramfs and relies on the clocks and pin muxing set up by U-Boot. Remarks concerning the earlycon support: - LinFlexD does not allow character transmissions in the INIT mode (see section 47.4.2.1 in the reference manual[1]). Therefore, a mutual exclusion between the first linflex_setup_watermark/linflex_set_termios executions and linflex_earlycon_putchar was employed and the characters normally sent to earlycon during initialization are kept in a buffer and sent afterwards. - Empirically, character transmission is also forbidden within the last 1-2 ms before entering the INIT mode, so we use an explicit timeout (PREINIT_DELAY) between linflex_earlycon_putchar and the first call to linflex_setup_watermark. - U-Boot currently uses the UART FIFO mode, while this driver makes the transition to the buffer mode. Therefore, the earlycon putchar function matches the U-Boot behavior before initializations and the Linux behavior after. [1] https://www.nxp.com/webapp/Download?colCode=S32V234RM Signed-off-by: Stoica Cosmin-Stefan Signed-off-by: Adrian.Nitu Signed-off-by: Larisa Grigore Signed-off-by: Ana Nedelcu Signed-off-by: Mihaela Martinas Signed-off-by: Matthew Nunez [stefan-gabriel.mirea@nxp.com: Reduced for upstreaming and implemented earlycon support] Signed-off-by: Stefan-Gabriel Mirea Link: https://lore.kernel.org/r/20190809112853.15846-6-stefan-gabriel.mirea@nxp.com Signed-off-by: Greg Kroah-Hartman --- Documentation/admin-guide/kernel-parameters.txt | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 47d981a86e2f..9ee66d61986b 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1090,6 +1090,12 @@ the framebuffer, pass the 'ram' option so that it is mapped with the correct attributes. + linflex, + Use early console provided by Freescale LinFlex UART + serial driver for NXP S32V234 SoCs. A valid base + address must be provided, and the serial port must + already be setup and configured. + earlyprintk= [X86,SH,ARM,M68k,S390] earlyprintk=vga earlyprintk=sclp -- cgit v1.2.3