[v5,0/7] Update Renesas {EMMA mobile, RZ/V2M} UART Port type

The Renesas {EMMA mobile, RZ/V2M} UART compatible with the general-purpose
16750 UART chip. This patch updates Renesas {EMMA mobile, RZ/V2M} UART type
from 16550a->16750 and also enables 64-bytes fifo.

This patch series also simplifies 8250_em_probe() and also updates the
register handling for the below restriction mentioned in the hardware
manual.

40.6.1 Point for Caution when Changing the Register Settings:

When changing the settings of the following registers, a PRESETn master
reset or FIFO reset + SW reset (FCR[2],FCR[1], HCR0[7]) must be input to
re-initialize them.

Target Registers: FCR, LCR, MCR, DLL, DLM, HCR0.

v4->v5:
 Ref: https://lore.kernel.org/linux-renesas-soc/20230217114255.226517-1-biju.das.jz@bp.renesas.com/T/#t 
 
 * Added fixes tag and reordered the patch (from patch#4 to patch#1) to make
   it easier for applying it to stable branches.
 * Updated commit header and descriptions.
 * Removed UPF_BOOT_AUTOCONF from flags.
 * Created a new patch for adding missing break statement in
   serial8250_em_serial_out().
 * On patch#6, retained UART_FCR in serial8250_em_serial_out().
 * Dropped UART_FCR from serial8250_em_serial_out_helper() as it is handled in
   serial8250_em_serial_out().
 * Fixed code alignment in serial8250_em_reg_update()
 * Added missing break statements.
v3->v4:
 * Split patch#1 to 3 patches and removed Rb tags.
 * Replaced dev_err->dev_err_probe() in probe()
 * Added a local variable 'dev' to replace '&pdev->dev' in probe().
 * Patch#2 removes unused header file slab.h.
 * Patch#3 simplifies clk handling in probe()/remove()
 * Removed sclk from struct serial8250_em_priv instead used local
   variable in probe()
 * Replaced devm_clk_get->devm_clk_get_enabled() and removed
   clk_prepare_enable/clk_disable_unprepare from probe()/remove().
 * Both {RZ/V2M, EMMA mobile} SoC is Register-compatible
   with the general-purpose 16750 UART chip. So started using
   generic compatible and removed struct serial8250_em_hw_info.
 * Introduced pseudo offset for UART_FCR(UART_FCR_EM) and used
   UART_FCR_EM in serial8250_em_serial{_in/_out} function to read/write
   FCR register.
 * Updated register update restriction to EMMA mobile SoC as well.
 * Replaced readl->serial8250_em_serial_in() for reading fcr register
   in serial8250_em_reg_update().
 * Added serial8250_em_serial_out_helper() to simplify the
   code and used for register writes in serial8250_em_reg_update().
v2->v3:
 * Dropped sclk from priv.
 * Dropped unneeded clk_disable_unprepare from remove().
 * Retained Rb tags from Geert,Andy and Ilpo as the changes are trivial.
 * Replaced of_device_get_match_data->device_get_match_data
 * Dropped struct serial8250_em_hw_info *info from priv and started
   using a local variable info in probe().
 * Retained Rb tag from Ilpo as changes are trivial.
 * Replaced readl/writel()->serial8250_em_serial_in/out() in serial8250_rzv2m_
   reg_update() to avoid duplication of offset trickery.
 * Added support for HCR0 read/write in serial8250_em_{serial_in, serial_out}
 * Added UART_LCR macro support in serial8250_em_serial_in() to read LCR
 * Reordered serial8250_em_{serial_in, serial_out} above serial8250_rzv2m_
   reg_update().
 * Replaced priv->info->serial_out to info->serial_out.
v1->v2:
 * Dropped patch#1 from previous series
 * Replaced devm_clk_get->devm_clk_get_enabled() and updated clk
   handling in probe().
 * Added Rb tag from Geert.
 * Added patch for updating Renesas RZ/V2M UART type from 16550a->16750
   and also enables 64-bytes fifo.
 * Used .data for taking h/w differences between EMMA mobile and RZ/V2M UART.
 * Added serial_out() to struct serial8250_em_hw_info for the write register
   differences between EMMA mobile and RZ/V2M UART.

Biju Das (7):
  serial: 8250_em: Fix UART port type
  serial: 8250_em: Simplify probe()
  serial: 8250_em: Drop unused header file
  serial: 8250_em: Add missing break statement
  serial: 8250_em: Use devm_clk_get_enabled()
  serial: 8250_em: Use pseudo offset for UART_FCR
  serial: 8250_em: Add serial8250_em_{reg_update(),out_helper()}

 drivers/tty/serial/8250/8250_em.c | 117 +++++++++++++++++++++++-------
 1 file changed, 92 insertions(+), 25 deletions(-)