Re: [PATCH 2/5] serial: s5p: Add Apple M1 support

[Mark Kettenis <mark.kettenis@xs4all.nl>]

> From: Simon Glass <sjg@chromium.org>
> Date: Sun, 19 Sep 2021 21:15:59 -0600
> 
> Hi Mark,
> 
> On Sat, 18 Sept 2021 at 07:55, Mark Kettenis <kettenis@openbsd.org> wrote:
> >
> > Apple M1 SoCs include an S5L UART which is a variant of the S5P
> > UART.  Add support for this variant and enable it by default
> > on Apple SoCs.
> >
> > Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
> > ---
> >  arch/arm/include/asm/arch-m1/clk.h  | 11 ++++++++
> >  arch/arm/include/asm/arch-m1/uart.h | 41 +++++++++++++++++++++++++++++
> >  arch/arm/mach-apple/board.c         |  5 ++++
> >  drivers/serial/Kconfig              |  2 +-
> >  drivers/serial/serial_s5p.c         | 22 ++++++++++++++++
> >  5 files changed, 80 insertions(+), 1 deletion(-)
> >  create mode 100644 arch/arm/include/asm/arch-m1/clk.h
> >  create mode 100644 arch/arm/include/asm/arch-m1/uart.h
> >
> > diff --git a/arch/arm/include/asm/arch-m1/clk.h b/arch/arm/include/asm/arch-m1/clk.h
> > new file mode 100644
> > index 0000000000..f4326d0c0f
> > --- /dev/null
> > +++ b/arch/arm/include/asm/arch-m1/clk.h
> > @@ -0,0 +1,11 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright (C) 2021 Mark Kettenis <kettenis@openbsd.org>
> > + */
> > +
> > +#ifndef __ASM_ARM_ARCH_CLK_H_
> > +#define __ASM_ARM_ARCH_CLK_H_
> > +
> > +unsigned long get_uart_clk(int dev_index);
> 
> comment? But this should be in a clock driver, unless you are trying
> to get a debug UART up ASAP with minimal code?
> 
> > +
> > +#endif
> > diff --git a/arch/arm/include/asm/arch-m1/uart.h b/arch/arm/include/asm/arch-m1/uart.h
> > new file mode 100644
> > index 0000000000..d2a17a221e
> > --- /dev/null
> > +++ b/arch/arm/include/asm/arch-m1/uart.h
> > @@ -0,0 +1,41 @@
> > +/* SPDX-License-Identifier: GPL-2.0+ */
> > +/*
> > + * (C) Copyright 2009 Samsung Electronics
> > + * Minkyu Kang <mk7.kang@samsung.com>
> > + * Heungjun Kim <riverful.kim@samsung.com>
> > + */
> > +
> > +#ifndef __ASM_ARCH_UART_H_
> > +#define __ASM_ARCH_UART_H_
> > +
> > +#ifndef __ASSEMBLY__
> > +/* baudrate rest value */
> > +union br_rest {
> > +       unsigned short  slot;           /* udivslot */
> > +       unsigned char   value;          /* ufracval */
> > +};
> > +
> > +struct s5p_uart {
> > +       unsigned int    ulcon;
> > +       unsigned int    ucon;
> > +       unsigned int    ufcon;
> > +       unsigned int    umcon;
> > +       unsigned int    utrstat;
> > +       unsigned int    uerstat;
> > +       unsigned int    ufstat;
> > +       unsigned int    umstat;
> > +       unsigned int    utxh;
> > +       unsigned int    urxh;
> > +       unsigned int    ubrdiv;
> > +       union br_rest   rest;
> > +       unsigned char   res3[0x3fd0];
> > +};
> > +
> > +static inline int s5p_uart_divslot(void)
> > +{
> > +       return 0;
> > +}
> > +
> > +#endif /* __ASSEMBLY__ */
> > +
> > +#endif
> > diff --git a/arch/arm/mach-apple/board.c b/arch/arm/mach-apple/board.c
> > index 0c8b35292e..8bc5c2f69e 100644
> > --- a/arch/arm/mach-apple/board.c
> > +++ b/arch/arm/mach-apple/board.c
> > @@ -156,3 +156,8 @@ ulong board_get_usable_ram_top(ulong total_size)
> >          */
> >         return 0x980000000;
> >  }
> > +
> > +unsigned long get_uart_clk(int dev_index)
> > +{
> > +       return 24000000;
> 
> Should add to devicetree for the driver
> 
> > +}
> > diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
> > index 93348c0929..c3ac773929 100644
> > --- a/drivers/serial/Kconfig
> > +++ b/drivers/serial/Kconfig
> > @@ -719,7 +719,7 @@ config ROCKCHIP_SERIAL
> >
> >  config S5P_SERIAL
> >         bool "Support for Samsung S5P UART"
> > -       depends on ARCH_EXYNOS || ARCH_S5PC1XX
> > +       depends on ARCH_APPLE || ARCH_EXYNOS || ARCH_S5PC1XX
> >         default y
> >         help
> >           Select this to enable Samsung S5P UART support.
> > diff --git a/drivers/serial/serial_s5p.c b/drivers/serial/serial_s5p.c
> > index 6d09952a5d..eb770d9b62 100644
> > --- a/drivers/serial/serial_s5p.c
> > +++ b/drivers/serial/serial_s5p.c
> > @@ -21,12 +21,21 @@
> >
> >  DECLARE_GLOBAL_DATA_PTR;
> >
> > +#ifdef CONFIG_ARCH_APPLE
> 
> This should use the compatible string to decide which variant it is,
> then the checks happen at runtime. We should never have arch-specific
> #ifdefs in drivers.
> 
> > +#define RX_FIFO_COUNT_SHIFT    0
> > +#define RX_FIFO_COUNT_MASK     (0xf << RX_FIFO_COUNT_SHIFT)
> > +#define RX_FIFO_FULL           (1 << 8)
> > +#define TX_FIFO_COUNT_SHIFT    4
> > +#define TX_FIFO_COUNT_MASK     (0xf << TX_FIFO_COUNT_SHIFT)
> > +#define TX_FIFO_FULL           (1 << 9)
> > +#else
> >  #define RX_FIFO_COUNT_SHIFT    0
> >  #define RX_FIFO_COUNT_MASK     (0xff << RX_FIFO_COUNT_SHIFT)
> >  #define RX_FIFO_FULL           (1 << 8)
> >  #define TX_FIFO_COUNT_SHIFT    16
> >  #define TX_FIFO_COUNT_MASK     (0xff << TX_FIFO_COUNT_SHIFT)
> >  #define TX_FIFO_FULL           (1 << 24)
> > +#endif
> >
> >  /* Information about a serial port */
> >  struct s5p_serial_plat {
> > @@ -83,7 +92,11 @@ static void __maybe_unused s5p_serial_baud(struct s5p_uart *uart, uint uclk,
> >         if (s5p_uart_divslot())
> >                 writew(udivslot[val % 16], &uart->rest.slot);
> >         else
> > +#ifdef CONFIG_ARCH_APPLE
> > +               writel(val % 16, &uart->rest.value);
> > +#else
> >                 writeb(val % 16, &uart->rest.value);
> > +#endif
> >  }
> >
> >  #ifndef CONFIG_SPL_BUILD
> > @@ -148,7 +161,11 @@ static int s5p_serial_getc(struct udevice *dev)
> >                 return -EAGAIN;
> >
> >         serial_err_check(uart, 0);
> > +#ifdef CONFIG_ARCH_APPLE
> > +       return (int)(readl(&uart->urxh) & 0xff);
> > +#else
> >         return (int)(readb(&uart->urxh) & 0xff);
> > +#endif
> >  }
> >
> >  static int s5p_serial_putc(struct udevice *dev, const char ch)
> > @@ -159,7 +176,11 @@ static int s5p_serial_putc(struct udevice *dev, const char ch)
> >         if (readl(&uart->ufstat) & TX_FIFO_FULL)
> >                 return -EAGAIN;
> >
> > +#ifdef CONFIG_ARCH_APPLE
> > +       writel(ch, &uart->utxh);
> > +#else
> >         writeb(ch, &uart->utxh);
> > +#endif
> >         serial_err_check(uart, 1);
> >
> >         return 0;
> > @@ -201,6 +222,7 @@ static const struct dm_serial_ops s5p_serial_ops = {
> >
> >  static const struct udevice_id s5p_serial_ids[] = {
> >         { .compatible = "samsung,exynos4210-uart" },
> > +       { .compatible = "apple,s5l-uart" },
> >         { }
> >  };
> >
> > --
> > 2.33.0
> >
> 
> Can you add debug UART support? Or does this already work?

I don't think it does work.  But yes, I want to add it since it will
help a lot with debugging.  That makes fixing some of the issues
raised by you and bing more problematic since the debug UART support
code:

- Needs to use 32-bit access on Apple M1, and using the "reg-io-width"
  property there isn't possible.

- Relies on the FIFO control bits which are in a different position on
  the Apple M1.

So I am starting to wonder whether it makes sense to simply copy
serial_s5p.c to serial_s5l.c and modify that one to do the right thing
on the apple SoC.

Alternatively I could introduce Kconfig stuff to switch between S5L
and S5P support.