powerpc/pseries: delete scanlog

Remove the pseries scanlog driver.

This code supports functions from Power4-era servers that are not present
on targets currently supported by arch/powerpc. System manuals from this
time have this description:

  Scan Dump data is a set of chip data that the service processor gathers
  after a system malfunction. It consists of chip scan rings, chip trace
  arrays, and Scan COM (SCOM) registers. This data is stored in the
  scan-log partition of the system’s Nonvolatile Random Access
  Memory (NVRAM).

PowerVM partition firmware development doesn't recognize the associated
function call or property, and they don't see any references to them in
their codebase. It seems to have been specific to non-virtualized pseries.

References:

Historical Linux commit from February 2003 (interesting to note this seems
to be the source of non-GPL exports for rtas_call etc):
https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=f92e361842d5251e50562b09664082dcbd0548bb

IntelliStation and pSeries docs which refer to the feature:
http://ps-2.retropc.se/basil.holloway/ALL%20PDF/380635.pdf
http://ps-2.kev009.com/rs6000/manuals/p/p615-6C3-6E3/6C3_and_6E3_Users_Guide_SA38-0629.pdfSigned-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210920173203.1800475-1-nathanl@linux.ibm.com

arch/powerpc/configs/ppc64_defconfig

@@ -26,7 +26,6 @@ CONFIG_PPC64=y
 CONFIG_NR_CPUS=2048
 CONFIG_PPC_SPLPAR=y
 CONFIG_DTL=y
-CONFIG_SCANLOG=m
 CONFIG_PPC_SMLPAR=y
 CONFIG_IBMEBUS=y
 CONFIG_PPC_SVM=y

arch/powerpc/configs/pseries_defconfig

@@ -38,7 +38,6 @@ CONFIG_MODULE_SRCVERSION_ALL=y
 CONFIG_PARTITION_ADVANCED=y
 CONFIG_PPC_SPLPAR=y
 CONFIG_DTL=y
-CONFIG_SCANLOG=m
 CONFIG_PPC_SMLPAR=y
 CONFIG_IBMEBUS=y
 CONFIG_PAPR_SCM=m

arch/powerpc/platforms/pseries/Kconfig

@@ -61,10 +61,6 @@ config PSERIES_ENERGY
 	  Provides: /sys/devices/system/cpu/pseries_(de)activation_hint_list
 	  and /sys/devices/system/cpu/cpuN/pseries_(de)activation_hint
 
-config SCANLOG
-	tristate "Scanlog dump interface"
-	depends on RTAS_PROC && PPC_PSERIES
-
 config IO_EVENT_IRQ
 	bool "IO Event Interrupt support"
 	depends on PPC_PSERIES

arch/powerpc/platforms/pseries/Makefile

@@ -8,7 +8,6 @@ obj-y			:= lpar.o hvCall.o nvram.o reconfig.o \
 			   firmware.o power.o dlpar.o mobility.o rng.o \
 			   pci.o pci_dlpar.o eeh_pseries.o msi.o
 obj-$(CONFIG_SMP)	+= smp.o
-obj-$(CONFIG_SCANLOG)	+= scanlog.o
 obj-$(CONFIG_KEXEC_CORE)	+= kexec.o
 obj-$(CONFIG_PSERIES_ENERGY)	+= pseries_energy.o
 

arch/powerpc/platforms/pseries/scanlog.c

-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- *  c 2001 PPC 64 Team, IBM Corp
- *
- * scan-log-data driver for PPC64  Todd Inglett <tinglett@vnet.ibm.com>
- *
- * When ppc64 hardware fails the service processor dumps internal state
- * of the system.  After a reboot the operating system can access a dump
- * of this data using this driver.  A dump exists if the device-tree
- * /chosen/ibm,scan-log-data property exists.
- *
- * This driver exports /proc/powerpc/scan-log-dump which can be read.
- * The driver supports only sequential reads.
- *
- * The driver looks at a write to the driver for the single word "reset".
- * If given, the driver will reset the scanlog so the platform can free it.
- */
-
-#include <linux/module.h>
-#include <linux/types.h>
-#include <linux/errno.h>
-#include <linux/proc_fs.h>
-#include <linux/init.h>
-#include <linux/delay.h>
-#include <linux/slab.h>
-#include <linux/uaccess.h>
-#include <asm/rtas.h>
-#include <asm/prom.h>
-
-#define MODULE_VERS "1.0"
-#define MODULE_NAME "scanlog"
-
-/* Status returns from ibm,scan-log-dump */
-#define SCANLOG_COMPLETE 0
-#define SCANLOG_HWERROR -1
-#define SCANLOG_CONTINUE 1
-
-
-static unsigned int ibm_scan_log_dump;			/* RTAS token */
-static unsigned int *scanlog_buffer;			/* The data buffer */
-
-static ssize_t scanlog_read(struct file *file, char __user *buf,
-			    size_t count, loff_t *ppos)
-{
-	unsigned int *data = scanlog_buffer;
-	int status;
-	unsigned long len, off;
-	unsigned int wait_time;
-
-	if (count > RTAS_DATA_BUF_SIZE)
-		count = RTAS_DATA_BUF_SIZE;
-
-	if (count < 1024) {
-		/* This is the min supported by this RTAS call.  Rather
-		 * than do all the buffering we insist the user code handle
-		 * larger reads.  As long as cp works... :)
-		 */
-		printk(KERN_ERR "scanlog: cannot perform a small read (%ld)\n", count);
-		return -EINVAL;
-	}
-
-	if (!access_ok(buf, count))
-		return -EFAULT;
-
-	for (;;) {
-		wait_time = 500;	/* default wait if no data */
-		spin_lock(&rtas_data_buf_lock);
-		memcpy(rtas_data_buf, data, RTAS_DATA_BUF_SIZE);
-		status = rtas_call(ibm_scan_log_dump, 2, 1, NULL,
-				   (u32) __pa(rtas_data_buf), (u32) count);
-		memcpy(data, rtas_data_buf, RTAS_DATA_BUF_SIZE);
-		spin_unlock(&rtas_data_buf_lock);
-
-		pr_debug("scanlog: status=%d, data[0]=%x, data[1]=%x, " \
-			 "data[2]=%x\n", status, data[0], data[1], data[2]);
-		switch (status) {
-		    case SCANLOG_COMPLETE:
-			pr_debug("scanlog: hit eof\n");
-			return 0;
-		    case SCANLOG_HWERROR:
-			pr_debug("scanlog: hardware error reading data\n");
-			return -EIO;
-		    case SCANLOG_CONTINUE:
-			/* We may or may not have data yet */
-			len = data[1];
-			off = data[2];
-			if (len > 0) {
-				if (copy_to_user(buf, ((char *)data)+off, len))
-					return -EFAULT;
-				return len;
-			}
-			/* Break to sleep default time */
-			break;
-		    default:
-			/* Assume extended busy */
-			wait_time = rtas_busy_delay_time(status);
-			if (!wait_time) {
-				printk(KERN_ERR "scanlog: unknown error " \
-				       "from rtas: %d\n", status);
-				return -EIO;
-			}
-		}
-		/* Apparently no data yet.  Wait and try again. */
-		msleep_interruptible(wait_time);
-	}
-	/*NOTREACHED*/
-}
-
-static ssize_t scanlog_write(struct file * file, const char __user * buf,
-			     size_t count, loff_t *ppos)
-{
-	char stkbuf[20];
-	int status;
-
-	if (count > 19) count = 19;
-	if (copy_from_user (stkbuf, buf, count)) {
-		return -EFAULT;
-	}
-	stkbuf[count] = 0;
-
-	if (buf) {
-		if (strncmp(stkbuf, "reset", 5) == 0) {
-			pr_debug("scanlog: reset scanlog\n");
-			status = rtas_call(ibm_scan_log_dump, 2, 1, NULL, 0, 0);
-			pr_debug("scanlog: rtas returns %d\n", status);
-		}
-	}
-	return count;
-}
-
-static int scanlog_open(struct inode * inode, struct file * file)
-{
-	unsigned int *data = scanlog_buffer;
-
-	if (data[0] != 0) {
-		/* This imperfect test stops a second copy of the
-		 * data (or a reset while data is being copied)
-		 */
-		return -EBUSY;
-	}
-
-	data[0] = 0;	/* re-init so we restart the scan */
-
-	return 0;
-}
-
-static int scanlog_release(struct inode * inode, struct file * file)
-{
-	unsigned int *data = scanlog_buffer;
-
-	data[0] = 0;
-	return 0;
-}
-
-static const struct proc_ops scanlog_proc_ops = {
-	.proc_read	= scanlog_read,
-	.proc_write	= scanlog_write,
-	.proc_open	= scanlog_open,
-	.proc_release	= scanlog_release,
-	.proc_lseek	= noop_llseek,
-};
-
-static int __init scanlog_init(void)
-{
-	struct proc_dir_entry *ent;
-	int err = -ENOMEM;
-
-	ibm_scan_log_dump = rtas_token("ibm,scan-log-dump");
-	if (ibm_scan_log_dump == RTAS_UNKNOWN_SERVICE)
-		return -ENODEV;
-
-	/* Ideally we could allocate a buffer < 4G */
-	scanlog_buffer = kzalloc(RTAS_DATA_BUF_SIZE, GFP_KERNEL);
-	if (!scanlog_buffer)
-		goto err;
-
-	ent = proc_create("powerpc/rtas/scan-log-dump", 0400, NULL,
-			  &scanlog_proc_ops);
-	if (!ent)
-		goto err;
-	return 0;
-err:
-	kfree(scanlog_buffer);
-	return err;
-}
-
-static void __exit scanlog_cleanup(void)
-{
-	remove_proc_entry("powerpc/rtas/scan-log-dump", NULL);
-	kfree(scanlog_buffer);
-}
-
-module_init(scanlog_init);
-module_exit(scanlog_cleanup);
-MODULE_LICENSE("GPL");