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Message-ID: <46d81b40dda20ada3b5847353a866172b419c811.camel@linux.ibm.com>
Date: Tue, 08 Oct 2024 10:16:25 +0200
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: "Maciej W. Rozycki" <macro@...am.me.uk>
Cc: Brian Cain <bcain@...cinc.com>, Marcel Holtmann <marcel@...tmann.org>,
Luiz Augusto von Dentz <luiz.dentz@...il.com>,
Patrik Jakobsson
<patrik.r.jakobsson@...il.com>,
Maarten Lankhorst
<maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Dave Airlie <airlied@...hat.com>, Gerd
Hoffmann <kraxel@...hat.com>,
Lucas De Marchi <lucas.demarchi@...el.com>,
Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Greg Kroah-Hartman
<gregkh@...uxfoundation.org>,
Jiri Slaby <jirislaby@...nel.org>, Arnd
Bergmann <arnd@...db.de>,
Heiko Carstens <hca@...ux.ibm.com>, linux-kernel@...r.kernel.org,
linux-hexagon@...r.kernel.org, linux-bluetooth@...r.kernel.org,
dri-devel@...ts.freedesktop.org, virtualization@...ts.linux.dev,
spice-devel@...ts.freedesktop.org, intel-xe@...ts.freedesktop.org,
linux-serial@...r.kernel.org, linux-arch@...r.kernel.org,
Arnd Bergmann <arnd@...nel.org>
Subject: Re: [PATCH v6 4/5] tty: serial: handle HAS_IOPORT dependencies
On Mon, 2024-10-07 at 22:09 +0100, Maciej W. Rozycki wrote:
> On Mon, 7 Oct 2024, Niklas Schnelle wrote:
>
> > diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
> > index 6709b6a5f3011db38acc58dc7223158fe4fcf72e..6a638feb44e443a1998980dd037748f227ec1bc8 100644
> > --- a/drivers/tty/serial/8250/8250_pci.c
> > +++ b/drivers/tty/serial/8250/8250_pci.c
> [...]
> > iobase = pci_resource_start(dev, 0);
> > outb(0x0, iobase + CH384_XINT_ENABLE_REG);
> > }
> >
> > -
> > static int
> > pci_sunix_setup(struct serial_private *priv,
> > const struct pciserial_board *board,
>
> Gratuitous change here.
>
> > diff --git a/drivers/tty/serial/8250/8250_pcilib.c b/drivers/tty/serial/8250/8250_pcilib.c
> > index ea906d721b2c3eac15c9e8d62cc6fa56c3ef6150..fc1882d7515b5814ff1240ffdbe1009ab908ad6b 100644
> > --- a/drivers/tty/serial/8250/8250_pcilib.c
> > +++ b/drivers/tty/serial/8250/8250_pcilib.c
> > @@ -28,6 +28,10 @@ int serial8250_pci_setup_port(struct pci_dev *dev, struct uart_8250_port *port,
> > port->port.membase = pcim_iomap_table(dev)[bar] + offset;
> > port->port.regshift = regshift;
> > } else {
> > + if (!IS_ENABLED(CONFIG_HAS_IOPORT)) {
> > + pr_err("Serial port %lx requires I/O port support\n", port->port.iobase);
> > + return -EINVAL;
> > + }
> > port->port.iotype = UPIO_PORT;
> > port->port.iobase = pci_resource_start(dev, bar) + offset;
> > port->port.mapbase = 0;
>
> Can we please flatten this conditional and get rid of the negation, and
> also use `pci_err' for clear identification (`port->port.iobase' may not
> even have been set to anything meaningful if this triggers)? I.e.:
>
> /* ... */
> } else if (IS_ENABLED(CONFIG_HAS_IOPORT)) {
> /* ... */
> } else {
> pci_err(dev, "serial port requires I/O port support\n");
> return -EINVAL;
> }
>
> I'd also say "port I/O" (by analogy to "memory-mapped I/O") rather than
> "I/O port", but I can imagine it might be debatable.
Agree this looks better, will change it.
>
> > +static __always_inline bool is_upf_fourport(struct uart_port *port)
> > +{
> > + if (!IS_ENABLED(CONFIG_HAS_IOPORT))
> > + return false;
> > +
> > + return port->flags & UPF_FOURPORT;
> > +}
>
> Can we perhaps avoid adding this helper and then tweaking code throughout
> by having:
>
> #ifdef CONFIG_SERIAL_8250_FOURPORT
> #define UPF_FOURPORT ((__force upf_t) ASYNC_FOURPORT /* 1 */ )
> #else
> #define UPF_FOURPORT 0
> #endif
>
> in include/linux/serial_core.h instead? I can see the flag is reused by
> drivers/tty/serial/sunsu.c, but from a glance over it seems rubbish to me
> and such a change won't hurt the driver anyway.
I'll look at this, do you think this is okay regarding matching the
user-space definitions in include/uapi/linux/tty_flags.h?
>
> > @@ -1174,7 +1201,7 @@ static void autoconfig(struct uart_8250_port *up)
> > */
> > scratch = serial_in(up, UART_IER);
> > serial_out(up, UART_IER, 0);
> > -#ifdef __i386__
> > +#if defined(__i386__) && defined(CONFIG_HAS_IOPORT)
> > outb(0xff, 0x080);
> > #endif
> > /*
> > @@ -1183,7 +1210,7 @@ static void autoconfig(struct uart_8250_port *up)
> > */
> > scratch2 = serial_in(up, UART_IER) & UART_IER_ALL_INTR;
> > serial_out(up, UART_IER, UART_IER_ALL_INTR);
> > -#ifdef __i386__
> > +#if defined(__i386__) && defined(CONFIG_HAS_IOPORT)
> > outb(0, 0x080);
> > #endif
> > scratch3 = serial_in(up, UART_IER) & UART_IER_ALL_INTR;
>
> Nah, i386 does have machine OUTB instructions, it has the port I/O
> address space in the ISA, so these two changes make no sense to me.
>
> Though this #ifdef should likely be converted to CONFIG_X86_32 via a
> separate change.
This is needed for Usermode Linux (UM) which sets __i386__ but also
doesn't have CONFIG_HAS_IOPORT. This was spotted by the kernel test bot
here: https://lore.kernel.org/all/202410031712.BwfGjrQY-lkp@intel.com/
>
> > @@ -1306,12 +1333,12 @@ static void autoconfig_irq(struct uart_8250_port *up)
> > {
> > struct uart_port *port = &up->port;
> > unsigned char save_mcr, save_ier;
> > + unsigned long irqs;
> > unsigned char save_ICP = 0;
> > unsigned int ICP = 0;
> > - unsigned long irqs;
> > int irq;
>
> Gratuitous change here (also breaking the reverse Christmas tree order).
>
> Thanks for making the clean-ups we discussed.
>
> Maciej
WIll drop this hunk
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