drivers/s390/char/sclp_con.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * SCLP line mode console driver
   4  *
   5  * Copyright IBM Corp. 1999, 2009
   6  * Author(s): Martin Peschke <mpeschke@de.ibm.com>
   7  *            Martin Schwidefsky <schwidefsky@de.ibm.com>
   8  */
   9
  10 #include <linux/kmod.h>
  11 #include <linux/console.h>
  12 #include <linux/init.h>
  13 #include <linux/panic_notifier.h>
  14 #include <linux/timer.h>
  15 #include <linux/jiffies.h>
  16 #include <linux/termios.h>
  17 #include <linux/err.h>
  18 #include <linux/reboot.h>
  19 #include <linux/gfp.h>
  20
  21 #include "sclp.h"
  22 #include "sclp_rw.h"
  23 #include "sclp_tty.h"
  24
  25 #define sclp_console_major 4            /* TTYAUX_MAJOR */
  26 #define sclp_console_minor 64
  27 #define sclp_console_name  "ttyS"
  28
  29 /* Lock to guard over changes to global variables */
  30 static DEFINE_SPINLOCK(sclp_con_lock);
  31 /* List of free pages that can be used for console output buffering */
  32 static LIST_HEAD(sclp_con_pages);
  33 /* List of full struct sclp_buffer structures ready for output */
  34 static LIST_HEAD(sclp_con_outqueue);
  35 /* Pointer to current console buffer */
  36 static struct sclp_buffer *sclp_conbuf;
  37 /* Timer for delayed output of console messages */
  38 static struct timer_list sclp_con_timer;
  39 /* Flag that output queue is currently running */
  40 static int sclp_con_queue_running;
  41
  42 /* Output format for console messages */
  43 #define SCLP_CON_COLUMNS        320
  44 #define SPACES_PER_TAB          8
  45
  46 static void
  47 sclp_conbuf_callback(struct sclp_buffer *buffer, int rc)
  48 {
  49         unsigned long flags;
  50         void *page;
  51
  52         do {
  53                 page = sclp_unmake_buffer(buffer);
  54                 spin_lock_irqsave(&sclp_con_lock, flags);
  55
  56                 /* Remove buffer from outqueue */
  57                 list_del(&buffer->list);
  58                 list_add_tail((struct list_head *) page, &sclp_con_pages);
  59
  60                 /* Check if there is a pending buffer on the out queue. */
  61                 buffer = NULL;
  62                 if (!list_empty(&sclp_con_outqueue))
  63                         buffer = list_first_entry(&sclp_con_outqueue,
  64                                                   struct sclp_buffer, list);
  65                 if (!buffer) {
  66                         sclp_con_queue_running = 0;
  67                         spin_unlock_irqrestore(&sclp_con_lock, flags);
  68                         break;
  69                 }
  70                 spin_unlock_irqrestore(&sclp_con_lock, flags);
  71         } while (sclp_emit_buffer(buffer, sclp_conbuf_callback));
  72 }
  73
  74 /*
  75  * Finalize and emit first pending buffer.
  76  */
  77 static void sclp_conbuf_emit(void)
  78 {
  79         struct sclp_buffer* buffer;
  80         unsigned long flags;
  81         int rc;
  82
  83         spin_lock_irqsave(&sclp_con_lock, flags);
  84         if (sclp_conbuf)
  85                 list_add_tail(&sclp_conbuf->list, &sclp_con_outqueue);
  86         sclp_conbuf = NULL;
  87         if (sclp_con_queue_running)
  88                 goto out_unlock;
  89         if (list_empty(&sclp_con_outqueue))
  90                 goto out_unlock;
  91         buffer = list_first_entry(&sclp_con_outqueue, struct sclp_buffer,
  92                                   list);
  93         sclp_con_queue_running = 1;
  94         spin_unlock_irqrestore(&sclp_con_lock, flags);
  95
  96         rc = sclp_emit_buffer(buffer, sclp_conbuf_callback);
  97         if (rc)
  98                 sclp_conbuf_callback(buffer, rc);
  99         return;
 100 out_unlock:
 101         spin_unlock_irqrestore(&sclp_con_lock, flags);
 102 }
 103
 104 /*
 105  * Wait until out queue is empty
 106  */
 107 static void sclp_console_sync_queue(void)
 108 {
 109         unsigned long flags;
 110
 111         spin_lock_irqsave(&sclp_con_lock, flags);
 112         if (timer_pending(&sclp_con_timer))
 113                 del_timer(&sclp_con_timer);
 114         while (sclp_con_queue_running) {
 115                 spin_unlock_irqrestore(&sclp_con_lock, flags);
 116                 sclp_sync_wait();
 117                 spin_lock_irqsave(&sclp_con_lock, flags);
 118         }
 119         spin_unlock_irqrestore(&sclp_con_lock, flags);
 120 }
 121
 122 /*
 123  * When this routine is called from the timer then we flush the
 124  * temporary write buffer without further waiting on a final new line.
 125  */
 126 static void
 127 sclp_console_timeout(struct timer_list *unused)
 128 {
 129         sclp_conbuf_emit();
 130 }
 131
 132 /*
 133  * Drop oldest console buffer if sclp_con_drop is set
 134  */
 135 static int
 136 sclp_console_drop_buffer(void)
 137 {
 138         struct list_head *list;
 139         struct sclp_buffer *buffer;
 140         void *page;
 141
 142         if (!sclp_console_drop)
 143                 return 0;
 144         list = sclp_con_outqueue.next;
 145         if (sclp_con_queue_running)
 146                 /* The first element is in I/O */
 147                 list = list->next;
 148         if (list == &sclp_con_outqueue)
 149                 return 0;
 150         list_del(list);
 151         buffer = list_entry(list, struct sclp_buffer, list);
 152         page = sclp_unmake_buffer(buffer);
 153         list_add_tail((struct list_head *) page, &sclp_con_pages);
 154         return 1;
 155 }
 156
 157 /*
 158  * Writes the given message to S390 system console
 159  */
 160 static void
 161 sclp_console_write(struct console *console, const char *message,
 162                    unsigned int count)
 163 {
 164         unsigned long flags;
 165         void *page;
 166         int written;
 167
 168         if (count == 0)
 169                 return;
 170         spin_lock_irqsave(&sclp_con_lock, flags);
 171         /*
 172          * process escape characters, write message into buffer,
 173          * send buffer to SCLP
 174          */
 175         do {
 176                 /* make sure we have a console output buffer */
 177                 if (sclp_conbuf == NULL) {
 178                         if (list_empty(&sclp_con_pages))
 179                                 sclp_console_full++;
 180                         while (list_empty(&sclp_con_pages)) {
 181                                 if (sclp_console_drop_buffer())
 182                                         break;
 183                                 spin_unlock_irqrestore(&sclp_con_lock, flags);
 184                                 sclp_sync_wait();
 185                                 spin_lock_irqsave(&sclp_con_lock, flags);
 186                         }
 187                         page = sclp_con_pages.next;
 188                         list_del((struct list_head *) page);
 189                         sclp_conbuf = sclp_make_buffer(page, SCLP_CON_COLUMNS,
 190                                                        SPACES_PER_TAB);
 191                 }
 192                 /* try to write the string to the current output buffer */
 193                 written = sclp_write(sclp_conbuf, (const unsigned char *)
 194                                      message, count);
 195                 if (written == count)
 196                         break;
 197                 /*
 198                  * Not all characters could be written to the current
 199                  * output buffer. Emit the buffer, create a new buffer
 200                  * and then output the rest of the string.
 201                  */
 202                 spin_unlock_irqrestore(&sclp_con_lock, flags);
 203                 sclp_conbuf_emit();
 204                 spin_lock_irqsave(&sclp_con_lock, flags);
 205                 message += written;
 206                 count -= written;
 207         } while (count > 0);
 208         /* Setup timer to output current console buffer after 1/10 second */
 209         if (sclp_conbuf != NULL && sclp_chars_in_buffer(sclp_conbuf) != 0 &&
 210             !timer_pending(&sclp_con_timer)) {
 211                 mod_timer(&sclp_con_timer, jiffies + HZ / 10);
 212         }
 213         spin_unlock_irqrestore(&sclp_con_lock, flags);
 214 }
 215
 216 static struct tty_driver *
 217 sclp_console_device(struct console *c, int *index)
 218 {
 219         *index = c->index;
 220         return sclp_tty_driver;
 221 }
 222
 223 /*
 224  * Make sure that all buffers will be flushed to the SCLP.
 225  */
 226 static void
 227 sclp_console_flush(void)
 228 {
 229         sclp_conbuf_emit();
 230         sclp_console_sync_queue();
 231 }
 232
 233 static int sclp_console_notify(struct notifier_block *self,
 234                                unsigned long event, void *data)
 235 {
 236         sclp_console_flush();
 237         return NOTIFY_OK;
 238 }
 239
 240 static struct notifier_block on_panic_nb = {
 241         .notifier_call = sclp_console_notify,
 242         .priority = 1,
 243 };
 244
 245 static struct notifier_block on_reboot_nb = {
 246         .notifier_call = sclp_console_notify,
 247         .priority = 1,
 248 };
 249
 250 /*
 251  * used to register the SCLP console to the kernel and to
 252  * give printk necessary information
 253  */
 254 static struct console sclp_console =
 255 {
 256         .name = sclp_console_name,
 257         .write = sclp_console_write,
 258         .device = sclp_console_device,
 259         .flags = CON_PRINTBUFFER,
 260         .index = 0 /* ttyS0 */
 261 };
 262
 263 /*
 264  * called by console_init() in drivers/char/tty_io.c at boot-time.
 265  */
 266 static int __init
 267 sclp_console_init(void)
 268 {
 269         void *page;
 270         int i;
 271         int rc;
 272
 273         /* SCLP consoles are handled together */
 274         if (!(CONSOLE_IS_SCLP || CONSOLE_IS_VT220))
 275                 return 0;
 276         rc = sclp_rw_init();
 277         if (rc)
 278                 return rc;
 279         /* Allocate pages for output buffering */
 280         for (i = 0; i < sclp_console_pages; i++) {
 281                 page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA);
 282                 list_add_tail(page, &sclp_con_pages);
 283         }
 284         sclp_conbuf = NULL;
 285         timer_setup(&sclp_con_timer, sclp_console_timeout, 0);
 286
 287         /* enable printk-access to this driver */
 288         atomic_notifier_chain_register(&panic_notifier_list, &on_panic_nb);
 289         register_reboot_notifier(&on_reboot_nb);
 290         register_console(&sclp_console);
 291         return 0;
 292 }
 293
 294 console_initcall(sclp_console_init);