9 files changed, 187 insertions, 2 deletions

diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt
index d758702fc03c..5f583af0a6e1 100644
--- a/Documentation/arm64/memory.txt
+++ b/Documentation/arm64/memory.txt
@@ -35,6 +35,8 @@ ffffffbc00000000	ffffffbdffffffff	   8GB		vmemmap
 
 ffffffbe00000000        ffffffbffbbfffff          ~8GB          [guard, future vmmemap]
 
+ffffffbffbc00000        ffffffbffbdfffff           2MB          earlyprintk device
+
 ffffffbffbe00000        ffffffbffbe0ffff          64KB          PCI I/O space
 
 ffffffbbffff0000        ffffffbcffffffff          ~2MB          [guard]
diff --git a/arch/arm64/Kconfig.debug b/arch/arm64/Kconfig.debug
index d7553f2bda66..79871cd78da8 100644
--- a/arch/arm64/Kconfig.debug
+++ b/arch/arm64/Kconfig.debug
@@ -24,4 +24,13 @@ config DEBUG_STACK_USAGE
           Enables the display of the minimum amount of free stack which each
           task has ever had available in the sysrq-T output.
 
+config EARLY_PRINTK
+        bool "Early printk support"
+        default y
+        help
+          Say Y here if you want to have an early console using the
+          earlyprintk=<name>[,<addr>][,<options>] kernel parameter. It
+          is assumed that the early console device has been initialised
+          by the boot loader prior to starting the Linux kernel.
+
 endmenu
diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
index d2f05a608274..57f12c991de2 100644
--- a/arch/arm64/include/asm/io.h
+++ b/arch/arm64/include/asm/io.h
@@ -230,6 +230,9 @@ extern void __iounmap(volatile void __iomem *addr);
 #define ioremap_wc(addr, size)          __ioremap((addr), (size), __pgprot(PROT_NORMAL_NC))
 #define iounmap                         __iounmap
 
+#define PROT_SECT_DEFAULT       (PMD_TYPE_SECT | PMD_SECT_AF)
+#define PROT_SECT_DEVICE_nGnRE  (PROT_SECT_DEFAULT | PTE_PXN | PTE_UXN | PMD_ATTRINDX(MT_DEVICE_nGnRE))
+
 #define ARCH_HAS_IOREMAP_WC
 #include <asm-generic/iomap.h>
 
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 1cac16a001cb..381f556b664e 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -43,6 +43,7 @@
 #define PAGE_OFFSET             UL(0xffffffc000000000)
 #define MODULES_END             (PAGE_OFFSET)
 #define MODULES_VADDR           (MODULES_END - SZ_64M)
+#define EARLYCON_IOBASE         (MODULES_VADDR - SZ_4M)
 #define VA_BITS                 (39)
 #define TASK_SIZE_64            (UL(1) << VA_BITS)
 
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index d4f7fd5b9e33..2494fc01896a 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -26,5 +26,6 @@ typedef struct {
 
 extern void paging_init(void);
 extern void setup_mm_for_reboot(void);
+extern void __iomem *early_io_map(phys_addr_t phys, unsigned long virt);
 
 #endif
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 74239c31e25a..a1cace45e970 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -17,6 +17,7 @@ arm64-obj-$(CONFIG_MODULES)		+= arm64ksyms.o module.o
 arm64-obj-$(CONFIG_SMP)                 += smp.o
 arm64-obj-$(CONFIG_HW_PERF_EVENTS)      += perf_event.o
 arm64-obj-$(CONFIG_HAVE_HW_BREAKPOINT)+= hw_breakpoint.o
+arm64-obj-$(CONFIG_EARLY_PRINTK)        += early_printk.o
 
 obj-y                                   += $(arm64-obj-y) vdso/
 obj-m                                   += $(arm64-obj-m)
diff --git a/arch/arm64/kernel/early_printk.c b/arch/arm64/kernel/early_printk.c
new file mode 100644
index 000000000000..7e320a2edb9b
--- /dev/null
+++ b/arch/arm64/kernel/early_printk.c
@@ -0,0 +1,118 @@
+/*
+ * Earlyprintk support.
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ * Author: Catalin Marinas <catalin.marinas@arm.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <linux/kernel.h>
+#include <linux/console.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/io.h>
+
+#include <linux/amba/serial.h>
+
+static void __iomem *early_base;
+static void (*printch)(char ch);
+
+/*
+ * PL011 single character TX.
+ */
+static void pl011_printch(char ch)
+{
+        while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_TXFF)
+                ;
+        writeb_relaxed(ch, early_base + UART01x_DR);
+        while (readl_relaxed(early_base + UART01x_FR) & UART01x_FR_BUSY)
+                ;
+}
+
+struct earlycon_match {
+        const char *name;
+        void (*printch)(char ch);
+};
+
+static const struct earlycon_match earlycon_match[] __initconst = {
+        { .name = "pl011", .printch = pl011_printch, },
+        {}
+};
+
+static void early_write(struct console *con, const char *s, unsigned n)
+{
+        while (n-- > 0) {
+                if (*s == '\n')
+                        printch('\r');
+                printch(*s);
+                s++;
+        }
+}
+
+static struct console early_console = {
+        .name =         "earlycon",
+        .write =        early_write,
+        .flags =        CON_PRINTBUFFER | CON_BOOT,
+        .index =        -1,
+};
+
+/*
+ * Parse earlyprintk=... parameter in the format:
+ *
+ *   <name>[,<addr>][,<options>]
+ *
+ * and register the early console. It is assumed that the UART has been
+ * initialised by the bootloader already.
+ */
+static int __init setup_early_printk(char *buf)
+{
+        const struct earlycon_match *match = earlycon_match;
+        phys_addr_t paddr = 0;
+
+        if (!buf) {
+                pr_warning("No earlyprintk arguments passed.\n");
+                return 0;
+        }
+
+        while (match->name) {
+                size_t len = strlen(match->name);
+                if (!strncmp(buf, match->name, len)) {
+                        buf += len;
+                        break;
+                }
+                match++;
+        }
+        if (!match->name) {
+                pr_warning("Unknown earlyprintk arguments: %s\n", buf);
+                return 0;
+        }
+
+        /* I/O address */
+        if (!strncmp(buf, ",0x", 3)) {
+                char *e;
+                paddr = simple_strtoul(buf + 1, &e, 16);
+                buf = e;
+        }
+        /* no options parsing yet */
+
+        if (paddr)
+                early_base = early_io_map(paddr, EARLYCON_IOBASE);
+
+        printch = match->printch;
+        register_console(&early_console);
+
+        return 0;
+}
+
+early_param("earlyprintk", setup_early_printk);
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 368ad1f7c36c..0a0a49756826 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -82,10 +82,8 @@
 
 #ifdef CONFIG_ARM64_64K_PAGES
 #define MM_MMUFLAGS     PTE_ATTRINDX(MT_NORMAL) | PTE_FLAGS
-#define IO_MMUFLAGS     PTE_ATTRINDX(MT_DEVICE_nGnRE) | PTE_XN | PTE_FLAGS
 #else
 #define MM_MMUFLAGS     PMD_ATTRINDX(MT_NORMAL) | PMD_FLAGS
-#define IO_MMUFLAGS     PMD_ATTRINDX(MT_DEVICE_nGnRE) | PMD_SECT_XN | PMD_FLAGS
 #endif
 
 /*
@@ -368,6 +366,7 @@ ENDPROC(__calc_phys_offset)
  *   - identity mapping to enable the MMU (low address, TTBR0)
  *   - first few MB of the kernel linear mapping to jump to once the MMU has
  *     been enabled, including the FDT blob (TTBR1)
+ *   - UART mapping if CONFIG_EARLY_PRINTK is enabled (TTBR1)
  */
 __create_page_tables:
         pgtbl   x25, x26, x24                   // idmap_pg_dir and swapper_pg_dir addresses
@@ -420,6 +419,15 @@ __create_page_tables:
         sub     x6, x6, #1                      // inclusive range
         create_block_map x0, x7, x3, x5, x6
 1:
+#ifdef CONFIG_EARLY_PRINTK
+        /*
+         * Create the pgd entry for the UART mapping. The full mapping is done
+         * later based earlyprintk kernel parameter.
+         */
+        ldr     x5, =EARLYCON_IOBASE            // UART virtual address
+        add     x0, x26, #2 * PAGE_SIZE         // section table address
+        create_pgd_entry x26, x0, x5, x6, x7
+#endif
         ret
 ENDPROC(__create_page_tables)
         .ltorg
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index a6885d896ab6..f4dd585898c5 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -25,6 +25,7 @@
 #include <linux/nodemask.h>
 #include <linux/memblock.h>
 #include <linux/fs.h>
+#include <linux/io.h>
 
 #include <asm/cputype.h>
 #include <asm/sections.h>
@@ -251,6 +252,47 @@ static void __init create_mapping(phys_addr_t phys, unsigned long virt,
         } while (pgd++, addr = next, addr != end);
 }
 
+#ifdef CONFIG_EARLY_PRINTK
+/*
+ * Create an early I/O mapping using the pgd/pmd entries already populated
+ * in head.S as this function is called too early to allocated any memory. The
+ * mapping size is 2MB with 4KB pages or 64KB or 64KB pages.
+ */
+void __iomem * __init early_io_map(phys_addr_t phys, unsigned long virt)
+{
+        unsigned long size, mask;
+        bool page64k = IS_ENABLED(ARM64_64K_PAGES);
+        pgd_t *pgd;
+        pud_t *pud;
+        pmd_t *pmd;
+        pte_t *pte;
+
+        /*
+         * No early pte entries with !ARM64_64K_PAGES configuration, so using
+         * sections (pmd).
+         */
+        size = page64k ? PAGE_SIZE : SECTION_SIZE;
+        mask = ~(size - 1);
+
+        pgd = pgd_offset_k(virt);
+        pud = pud_offset(pgd, virt);
+        if (pud_none(*pud))
+                return NULL;
+        pmd = pmd_offset(pud, virt);
+
+        if (page64k) {
+                if (pmd_none(*pmd))
+                        return NULL;
+                pte = pte_offset_kernel(pmd, virt);
+                set_pte(pte, __pte((phys & mask) | PROT_DEVICE_nGnRE));
+        } else {
+                set_pmd(pmd, __pmd((phys & mask) | PROT_SECT_DEVICE_nGnRE));
+        }
+
+        return (void __iomem *)((virt & mask) + (phys & ~mask));
+}
+#endif
+
 static void __init map_mem(void)
 {
         struct memblock_region *reg;