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Stefan-gabriel Mirea authored
Introduce support for LINFlex driver, based on: - the version of Freescale LPUART driver after commit b3e3bf2e ("Merge 4.0-rc7 into tty-next"); - commit abf1e0a9 ("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=S32V234RMSigned-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.comSigned-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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