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Message-ID: <20150527231426.GA105692@worksta>
Date: Wed, 27 May 2015 16:14:26 -0700
From: Bin Gao <bin.gao@...ux.intel.com>
To: Peter Hurley <peter@...leysoftware.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jiri Slaby <jslaby@...e.cz>,
One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
linux-kernel@...r.kernel.org,
"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH v4 1/2] serial_core: add pci uart early console support
Peter Hurley,
First of all, thank you for your reviewing.
Please see my answers below.
On Tue, May 26, 2015 at 01:12:34PM -0400, Peter Hurley wrote:
> Hi Bin,
>
> Please don't drop lists (or other addressees) from patch revisions.
>
> [ +cc linux-serial]
Will fix this.
> Please update Documentation/kernel-parameters.txt with pci-specific
> earlycon parameter formats.
Will do.
> Please move this hunk to patch 2/2.
It's already in 2/2. Or I'm not quite understanding?
> FYI, there is a proposal to evaluate "earlyprintk=" earlier than
> parse_early_params(), which this would break.
>
> https://lkml.org/lkml/2015/5/18/127
No, it wouldn't. The proposal only moves earlyprintk=serial(legacy 0x3f8).
If you look into arch/x86/kernel/early_printk.c, you'll find many other
options other than serial, e.g. vga, dbgp, xen, efi, pciserial, etc.
uart8250(previously pciserial) is one of these "others".
> > +static int parse_bdf(char *options, char **endp, char delimiter, u8 *val)
>
> If this function is only used from parse_pci_options(), please enclose it
> in #ifdef CONFIG_PCI_EARLY scope with parse_pci_options().
Yes, will fix it.
>
> > +{
> > + char str[4]; /* max 3 chars, plus a NULL terminator */
> > + char *p = options;
> > + int i = 0;
> > +
> > + while (*p) {
> > + if (i >= 4)
> > + return -EINVAL;
> > +
> > + if (*p == delimiter) {
> > + str[i++] = 0;
> > + if (endp)
> > + *endp = p + 1;
> > + return kstrtou8(str, 10, val); /* decimal, no hex */
> > + }
> > +
> > + str[i++] = *p++;
> > + }
>
> Is all this to avoid using simple_strtoul()?
> If yes, I'd rather you use simple_strtoul() like the rest of the console
> code and ignore the (misguided) advice that simple_strtoul() is obsolete.
Then scripts/checkpatch.pl should be updated to avoid this kind of "misguiding".
Also the kstrto* API descriptions should be updated...
> The code above is exactly what is wrong with the kstrto* api.
Can you elaborate a little bit? Thanks.
> > + if (!early_pci_allowed()) {
> > + pr_err("earlycon pci not available(early pci not allowed)\n");
>
> Error message is redundant.
"early pci not allowed" is the reason of "earlycon pci not available".
> > + /*
> > + * On these platforms class code in pci config is broken,
> ^^^^^^^^^^^^^^^
> which platforms?
On platforms where this code will run on.
Do you prefer something like:
On platforms with early pci serial class code in pci config is broken,
> > + pr_info("Use 8250 uart at PCI 0000:%02u:%02u.%01u as early console\n",
> > + bus, dev, func);
>
> I think one earlycon banner is sufficient; you could make this pr_debug()
> instead. Existing convention for earlycon messages is
>
> "earlycon: ...."
Will use pr_debug().
> > * @options: ptr for <options> field; NULL if not present (out)
> > *
> > * Decodes earlycon kernel command line parameters of the form
> > - * earlycon=<name>,io|mmio|mmio32,<addr>,<options>
> > + * earlycon=<name>,io|mmio|mmio32|pci|pci32,<addr>,<options>
>
> Document the pci/pci32 format separately because
> earlycon=uart8250,pci32,<addr>,<options> is not a valid form.
Why it's not a valid form? It follows the existed syntax like this:
earlycon=uart8250,<io type>,<addr>,<options>
> > @@ -1829,12 +1939,23 @@ uart_get_console(struct uart_port *ports, int nr, struct console *co)
> > int uart_parse_earlycon(char *p, unsigned char *iotype, unsigned long *addr,
> > char **options)
> > {
> > + int pci = 0, ret;
> > + unsigned long phys;
> > +
> > if (strncmp(p, "mmio,", 5) == 0) {
> > *iotype = UPIO_MEM;
> > p += 5;
> > } else if (strncmp(p, "mmio32,", 7) == 0) {
> > *iotype = UPIO_MEM32;
> > p += 7;
> > + } else if (strncmp(p, "pci,", 4) == 0) {
> > + pci = 1;
> > + p += 4;
> > + ret = parse_pci_options(p, &phys);
> > + } else if (strncmp(p, "pci32,", 6) == 0) {
> > + pci = 2;
> > + p += 6;
> > + ret = parse_pci_options(p, &phys);
> > } else if (strncmp(p, "io,", 3) == 0) {
> > *iotype = UPIO_PORT;
> > p += 3;
> > @@ -1844,7 +1965,27 @@ int uart_parse_earlycon(char *p, unsigned char *iotype, unsigned long *addr,
> > return -EINVAL;
> > }
> >
> > - *addr = simple_strtoul(p, NULL, 0);
> > + if (pci) {
> > + if (ret < 0) /* error */
> > + return ret;
> > +
> > + /*
> > + * Once PCI mem/io is read from PCI BAR, we can reuse
> > + * mmio/mmio32/io type to minimize code change.
> > + */
> > + if (ret > 0) /* PCI io */
> > + *iotype = UPIO_PORT;
> > + else { /* ret = 0: PCI mem */
> > + if (pci == 2)
> > + *iotype = UPIO_MEM32;
> > + else
> > + *iotype = UPIO_MEM;
> > + }
> > +
> > + *addr = phys;
> > + } else
> > + *addr = simple_strtoul(p, NULL, 0);
> > +
>
> I'd like to see this refactored without the logic steering locals.
> Like this:
>
> if (strncmp(p, "mmio,", 5) == 0) {
> *iotype = UPIO_MEM;
> p += 5;
> + *addr = simple_strtoul(p, NULL, 0);
> } else if (strncmp(p, "mmio32,", 7) == 0) {
> *iotype = UPIO_MEM32;
> p += 7;
> + *addr = simple_strtoul(p, NULL, 0);
> + } else if (strncmp(p, "pci,", 4) == 0) {
> + pci = 1;
> + p += 4;
> + ret = parse_pci_options(p, addr);
> + if (ret < 0)
> + return ret;
> + *iotype = (ret > 0) ? UPIO_PORT : UPIO_MEM;
> + } else if (strncmp(p, "pci32,", 6) == 0) {
> + pci = 2;
> + p += 6;
> + ret = parse_pci_options(p, addr);
> + if (ret < 0)
> + return ret;
> + *iotype = (ret > 0) ? UPIO_PORT : UPIO_MEM32;
> } else if (strncmp(p, "io,", 3) == 0) {
> *iotype = UPIO_PORT;
> p += 3;
> + *addr = simple_strtoul(p, NULL, 0);
>
>
> Regards,
> Peter Hurley
>
> > - *addr = simple_strtoul(p, NULL, 0);
> > p = strchr(p, ',');
> > if (p)
> > p++;
> >
Ah, this is kind of coding style. But I agree with your suggestion. Will fix it.
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