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authorStefan-gabriel Mirea <stefan-gabriel.mirea@nxp.com>2019-08-09 14:29:16 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-09-04 13:43:54 +0300
commit09864c1cdf5c537bd01bff45181406e422ea988c (patch)
treea646e147848688a6edd6181029d200cf4b85ab2e /Documentation/admin-guide
parent8d41ab87630bdd249996a7ec1f138a23bcd2f5ff (diff)
downloadlinux-09864c1cdf5c537bd01bff45181406e422ea988c.tar.xz
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 <cosmin.stoica@nxp.com> Signed-off-by: Adrian.Nitu <adrian.nitu@freescale.com> Signed-off-by: Larisa Grigore <Larisa.Grigore@nxp.com> Signed-off-by: Ana Nedelcu <B56683@freescale.com> Signed-off-by: Mihaela Martinas <Mihaela.Martinas@freescale.com> Signed-off-by: Matthew Nunez <matthew.nunez@nxp.com> [stefan-gabriel.mirea@nxp.com: Reduced for upstreaming and implemented earlycon support] Signed-off-by: Stefan-Gabriel Mirea <stefan-gabriel.mirea@nxp.com> Link: https://lore.kernel.org/r/20190809112853.15846-6-stefan-gabriel.mirea@nxp.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/admin-guide')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt6
1 files changed, 6 insertions, 0 deletions
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,<addr>
+ 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