[PATCH v1 1/2] mmc: Support kmsg dumper based on pstore/blk

[Bhaskara Budiredla]

This patch introduces to mmcpstore. The functioning of mmcpstore is
is similar to mtdpstore. mmcpstore works on FTL based flash devices
whereas mtdpstore works on raw flash devices. When the system crashes,
mmcpstore stores the kmsg panic and oops logs to a user specified
MMC device.

It collects the details about the host MMC device through pstore/blk
"blkdev" parameter. The user can specify the MMC device in many ways
by checking in Documentation/admin-guide/pstore-blk.rst.

The individual mmc host drivers have to define suitable polling
subroutines to write kmsg panic/oops logs through mmcpstore.

Signed-off-by: Bhaskara Budiredla <bbudiredla@xxxxxxxxxxx>
---
 drivers/mmc/core/Kconfig     |   7 +
 drivers/mmc/core/Makefile    |   1 +
 drivers/mmc/core/block.c     |  20 +++
 drivers/mmc/core/block.h     |   3 +
 drivers/mmc/core/core.c      |  24 +++
 drivers/mmc/core/mmcpstore.c | 318 +++++++++++++++++++++++++++++++++++
 include/linux/mmc/card.h     |   4 +
 include/linux/mmc/core.h     |   4 +
 include/linux/mmc/host.h     |   6 +
 9 files changed, 387 insertions(+)
 create mode 100644 drivers/mmc/core/mmcpstore.c

diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig
index c12fe13e4b14..cafb367c482d 100644
--- a/drivers/mmc/core/Kconfig
+++ b/drivers/mmc/core/Kconfig
@@ -81,3 +81,10 @@ config MMC_TEST
 	  This driver is only of interest to those developing or
 	  testing a host driver. Most people should say N here.
 
+config MMC_PSTORE
+	bool "Log panic/oops to a MMC buffer"
+	depends on PSTORE
+	depends on PSTORE_BLK
+	help
+	  Backend driver to store the kmsg crash dumps to a user specified MMC
+	  device. The driver is based on pstore/blk.
diff --git a/drivers/mmc/core/Makefile b/drivers/mmc/core/Makefile
index 95ffe008ebdf..5f4230b79ac6 100644
--- a/drivers/mmc/core/Makefile
+++ b/drivers/mmc/core/Makefile
@@ -17,4 +17,5 @@ mmc_core-$(CONFIG_DEBUG_FS)	+= debugfs.o
 obj-$(CONFIG_MMC_BLOCK)		+= mmc_block.o
 mmc_block-objs			:= block.o queue.o
 obj-$(CONFIG_MMC_TEST)		+= mmc_test.o
+obj-$(CONFIG_MMC_PSTORE)	+= mmcpstore.o
 obj-$(CONFIG_SDIO_UART)		+= sdio_uart.o
diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
index 8d3df0be0355..f11c21d60b67 100644
--- a/drivers/mmc/core/block.c
+++ b/drivers/mmc/core/block.c
@@ -2870,6 +2870,21 @@ static void mmc_blk_remove_debugfs(struct mmc_card *card,
 
 #endif /* CONFIG_DEBUG_FS */
 
+#ifdef CONFIG_MMC_PSTORE
+sector_t mmc_blk_get_part(struct mmc_card *card, int part_num, sector_t *size)
+{
+	struct mmc_blk_data *md = dev_get_drvdata(&card->dev);
+	struct gendisk *disk = md->disk;
+	struct disk_part_tbl *part_tbl = disk->part_tbl;
+
+	if (part_num < 0 || part_num >= part_tbl->len)
+		return 0;
+
+	*size = part_tbl->part[part_num]->nr_sects << SECTOR_SHIFT;
+	return part_tbl->part[part_num]->start_sect;
+}
+#endif
+
 static int mmc_blk_probe(struct mmc_card *card)
 {
 	struct mmc_blk_data *md, *part_md;
@@ -2913,6 +2928,11 @@ static int mmc_blk_probe(struct mmc_card *card)
 			goto out;
 	}
 
+#ifdef CONFIG_MMC_PSTORE
+	if (mmc_card_mmc(card) || mmc_card_sd(card))
+		mmcpstore_card_set(card, md->disk->disk_name);
+#endif
+
 	/* Add two debugfs entries */
 	mmc_blk_add_debugfs(card, md);
 
diff --git a/drivers/mmc/core/block.h b/drivers/mmc/core/block.h
index 31153f656f41..2a2b81635508 100644
--- a/drivers/mmc/core/block.h
+++ b/drivers/mmc/core/block.h
@@ -16,5 +16,8 @@ void mmc_blk_mq_recovery(struct mmc_queue *mq);
 struct work_struct;
 
 void mmc_blk_mq_complete_work(struct work_struct *work);
+#ifdef CONFIG_MMC_PSTORE
+sector_t mmc_blk_get_part(struct mmc_card *card, int part_num, sector_t *size);
+#endif
 
 #endif
diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index d42037f0f10d..7cc3d81f6a9a 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -569,6 +569,30 @@ int mmc_cqe_recovery(struct mmc_host *host)
 }
 EXPORT_SYMBOL(mmc_cqe_recovery);
 
+
+#ifdef CONFIG_MMC_PSTORE
+/**
+ *	mmc_wait_for_pstore_req - initiate a blocking mmc request
+ *	@host: MMC host to start command
+ *	@mrq: MMC request to start
+ *
+ *	Start a new MMC custom command request for a host, and
+ *	wait for the command to complete based on request data timeout.
+ */
+void mmc_wait_for_pstore_req(struct mmc_host *host, struct mmc_request *mrq)
+{
+	unsigned int timeout;
+
+	host->ops->req_cleanup_pending(host);
+	mmc_start_request(host, mrq);
+
+	if (mrq->data) {
+		timeout = mrq->data->timeout_ns / NSEC_PER_MSEC;
+		host->ops->req_completion_poll(host, timeout);
+	}
+}
+#endif
+
 /**
  *	mmc_is_req_done - Determine if a 'cap_cmd_during_tfr' request is done
  *	@host: MMC host
diff --git a/drivers/mmc/core/mmcpstore.c b/drivers/mmc/core/mmcpstore.c
new file mode 100644
index 000000000000..ffa44c859e10
--- /dev/null
+++ b/drivers/mmc/core/mmcpstore.c
@@ -0,0 +1,318 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pstore_blk.h>
+#include <linux/blkdev.h>
+#include <linux/mount.h>
+#include <linux/slab.h>
+#include <linux/mmc/mmc.h>
+#include <linux/mmc/host.h>
+#include <linux/mmc/card.h>
+#include <linux/scatterlist.h>
+#include "block.h"
+#include "card.h"
+#include "core.h"
+
+static struct mmcpstore_context {
+	char dev_name[BDEVNAME_SIZE];
+	int partno;
+	sector_t start_sect;
+	sector_t size;
+	struct pstore_device_info dev;
+	struct pstore_blk_config conf;
+	struct pstore_blk_info info;
+
+	char *sub;
+	struct mmc_card	*card;
+	struct mmc_request *mrq;
+} oops_cxt;
+
+static void mmc_prep_req(struct mmc_request *mrq,
+		unsigned int sect_offset, unsigned int nsects,
+		struct scatterlist *sg, u32 opcode, unsigned int flags)
+{
+	mrq->cmd->opcode = opcode;
+	mrq->cmd->arg = sect_offset;
+	mrq->cmd->flags = MMC_RSP_R1 | MMC_CMD_ADTC;
+
+	if (nsects == 1) {
+		mrq->stop = NULL;
+	} else {
+		mrq->stop->opcode = MMC_STOP_TRANSMISSION;
+		mrq->stop->arg = 0;
+		mrq->stop->flags = MMC_RSP_R1B | MMC_CMD_AC;
+	}
+
+	mrq->data->blksz = SECTOR_SIZE;
+	mrq->data->blocks = nsects;
+	mrq->data->flags = flags;
+	mrq->data->sg = sg;
+	mrq->data->sg_len = 1;
+}
+
+static int mmcpstore_rdwr_req(const char *buf, unsigned int nsects,
+			unsigned int sect_offset, unsigned int flags)
+{
+	struct mmcpstore_context *cxt = &oops_cxt;
+	struct mmc_request *mrq = cxt->mrq;
+	struct mmc_card *card = cxt->card;
+	struct mmc_host *host = card->host;
+	struct scatterlist sg;
+	u32 opcode;
+
+	if (flags == MMC_DATA_READ)
+		opcode	= (nsects > 1) ?
+			MMC_READ_MULTIPLE_BLOCK : MMC_READ_SINGLE_BLOCK;
+	else
+		opcode = (nsects > 1) ?
+			MMC_WRITE_MULTIPLE_BLOCK : MMC_WRITE_BLOCK;
+
+	mmc_prep_req(mrq, sect_offset, nsects, &sg, opcode, flags);
+	sg_init_one(&sg, buf, (nsects << SECTOR_SHIFT));
+	mmc_set_data_timeout(mrq->data, cxt->card);
+
+	mmc_claim_host(host);
+	mmc_wait_for_req(host, mrq);
+	mdelay(mrq->data->timeout_ns / NSEC_PER_MSEC);
+	mmc_release_host(host);
+
+	if (mrq->cmd->error) {
+		pr_err("Cmd error: %d\n", mrq->cmd->error);
+		return mrq->cmd->error;
+	}
+	if (mrq->data->error) {
+		pr_err("Data error: %d\n", mrq->data->error);
+		return mrq->data->error;
+	}
+
+	return 0;
+}
+
+static ssize_t mmcpstore_write(const char *buf, size_t size, loff_t off)
+{
+	struct mmcpstore_context *cxt = &oops_cxt;
+	int ret;
+
+	ret = mmcpstore_rdwr_req(buf, (size >> SECTOR_SHIFT),
+		cxt->start_sect + (off >> SECTOR_SHIFT), MMC_DATA_WRITE);
+	if (ret)
+		return ret;
+
+	return size;
+}
+
+static ssize_t mmcpstore_read(char *buf, size_t size, loff_t off)
+{
+	struct mmcpstore_context *cxt = &oops_cxt;
+	unsigned int sect_off = cxt->start_sect  + (off >> SECTOR_SHIFT);
+	unsigned long sects = (cxt->conf.kmsg_size >> SECTOR_SHIFT);
+	int ret;
+
+	if (unlikely(!buf || !size))
+		return -EINVAL;
+
+	ret = mmcpstore_rdwr_req(cxt->sub, sects, sect_off, MMC_DATA_READ);
+	if (ret)
+		return ret;
+	memcpy(buf, cxt->sub, size);
+
+	return size;
+}
+
+static void mmcpstore_panic_write_req(const char *buf,
+		unsigned int nsects, unsigned int sect_offset)
+{
+	struct mmcpstore_context *cxt = &oops_cxt;
+	struct mmc_request *mrq = cxt->mrq;
+	struct mmc_card *card = cxt->card;
+	struct mmc_host *host = card->host;
+	struct scatterlist sg;
+	u32 opcode;
+
+	opcode = (nsects > 1) ? MMC_WRITE_MULTIPLE_BLOCK : MMC_WRITE_BLOCK;
+	mmc_prep_req(mrq, sect_offset, nsects, &sg, opcode, MMC_DATA_WRITE);
+	sg_init_one(&sg, buf, (nsects << SECTOR_SHIFT));
+	mmc_set_data_timeout(mrq->data, cxt->card);
+
+	mmc_claim_host(host);
+	mmc_wait_for_pstore_req(host, mrq);
+	mmc_release_host(card->host);
+}
+
+static ssize_t mmcpstore_panic_write(const char *buf, size_t size, loff_t off)
+{
+	struct mmcpstore_context *cxt = &oops_cxt;
+
+	mmcpstore_panic_write_req(buf, (size >> SECTOR_SHIFT),
+			cxt->start_sect + (off >> SECTOR_SHIFT));
+	return size;
+}
+
+static struct block_device *mmcpstore_open_backend(const char *device)
+{
+	struct block_device *bdev;
+	dev_t devt;
+
+	bdev = blkdev_get_by_path(device, FMODE_READ, NULL);
+	if (IS_ERR(bdev)) {
+		devt = name_to_dev_t(device);
+		if (devt == 0)
+			return ERR_PTR(-ENODEV);
+
+		bdev = blkdev_get_by_dev(devt, FMODE_READ, NULL);
+		if (IS_ERR(bdev))
+			return bdev;
+	}
+
+	return bdev;
+}
+
+static void mmcpstore_close_backend(struct block_device *bdev)
+{
+	if (!bdev)
+		return;
+	blkdev_put(bdev, FMODE_READ);
+}
+
+void mmcpstore_card_set(struct mmc_card *card, const char *disk_name)
+{
+	struct mmcpstore_context *cxt = &oops_cxt;
+	struct pstore_blk_config *conf = &cxt->conf;
+	struct pstore_device_info *dev = &cxt->dev;
+	struct block_device *bdev;
+	struct mmc_command *stop;
+	struct mmc_command *cmd;
+	struct mmc_request *mrq;
+	struct mmc_data *data;
+	int ret;
+
+	if (!conf->device[0])
+		return;
+
+	/* Multiple backend devices not allowed */
+	if (cxt->dev_name[0])
+		return;
+
+	bdev =  mmcpstore_open_backend(conf->device);
+	if (IS_ERR(bdev)) {
+		pr_err("%s failed to open with %ld\n",
+				conf->device, PTR_ERR(bdev));
+		return;
+	}
+
+	bdevname(bdev, cxt->dev_name);
+	cxt->partno = bdev->bd_part->partno;
+	mmcpstore_close_backend(bdev);
+
+	if (strncmp(cxt->dev_name, disk_name, strlen(disk_name)))
+		return;
+
+	cxt->start_sect = mmc_blk_get_part(card, cxt->partno, &cxt->size);
+	if (!cxt->start_sect) {
+		pr_err("Non-existent partition %d selected\n", cxt->partno);
+		return;
+	}
+
+	/* Check for host mmc panic write polling function definitions */
+	if (!card->host->ops->req_cleanup_pending ||
+			!card->host->ops->req_completion_poll)
+		return;
+
+	cxt->card = card;
+
+	cxt->sub = kmalloc(conf->kmsg_size, GFP_KERNEL);
+	if (!cxt->sub)
+		goto out;
+
+	mrq = kzalloc(sizeof(struct mmc_request), GFP_KERNEL);
+	if (!mrq)
+		goto free_sub;
+
+	cmd = kzalloc(sizeof(struct mmc_command), GFP_KERNEL);
+	if (!cmd)
+		goto free_mrq;
+
+	stop = kzalloc(sizeof(struct mmc_command), GFP_KERNEL);
+	if (!stop)
+		goto free_cmd;
+
+	data = kzalloc(sizeof(struct mmc_data), GFP_KERNEL);
+	if (!data)
+		goto free_stop;
+
+	mrq->cmd = cmd;
+	mrq->data = data;
+	mrq->stop = stop;
+	cxt->mrq = mrq;
+
+	dev->total_size = cxt->size;
+	dev->flags = PSTORE_FLAGS_DMESG;
+	dev->read = mmcpstore_read;
+	dev->write = mmcpstore_write;
+	dev->erase = NULL;
+	dev->panic_write = mmcpstore_panic_write;
+
+	ret = register_pstore_device(&cxt->dev);
+	if (ret) {
+		pr_err("%s registering with psblk failed (%d)\n",
+				cxt->dev_name, ret);
+		goto free_data;
+	}
+
+	pr_info("%s registered as psblk backend\n", cxt->dev_name);
+	return;
+
+free_data:
+	kfree(data);
+free_stop:
+	kfree(stop);
+free_cmd:
+	kfree(cmd);
+free_mrq:
+	kfree(mrq);
+free_sub:
+	kfree(cxt->sub);
+out:
+	return;
+}
+EXPORT_SYMBOL(mmcpstore_card_set);
+
+static int __init mmcpstore_init(void)
+{
+	struct mmcpstore_context *cxt = &oops_cxt;
+	struct pstore_blk_config *conf = &cxt->conf;
+	int err;
+
+	err = pstore_blk_get_config(conf);
+	if (unlikely(err))
+		return err;
+
+	if (!conf->device[0]) {
+		pr_err("psblk backend is empty\n");
+		return -EINVAL;
+	}
+
+	return err;
+}
+
+static void __exit mmcpstore_exit(void)
+{
+	struct mmcpstore_context *cxt = &oops_cxt;
+
+	unregister_pstore_device(&cxt->dev);
+	kfree(cxt->mrq->data);
+	kfree(cxt->mrq->stop);
+	kfree(cxt->mrq->cmd);
+	kfree(cxt->mrq);
+	kfree(cxt->sub);
+	cxt->card = NULL;
+}
+
+module_init(mmcpstore_init);
+module_exit(mmcpstore_exit);
+
+MODULE_AUTHOR("Bhaskara Budiredla <bbudiredla@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("MMC backend for pstore/blk");
diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index 42df06c6b19c..76ae8ae61d31 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -322,6 +322,10 @@ static inline bool mmc_large_sector(struct mmc_card *card)
 
 bool mmc_card_is_blockaddr(struct mmc_card *card);
 
+#ifdef CONFIG_MMC_PSTORE
+void mmcpstore_card_set(struct mmc_card *card, const char *disk_name);
+#endif /* CONFIG_MMC_PSTORE */
+
 #define mmc_card_mmc(c)		((c)->type == MMC_TYPE_MMC)
 #define mmc_card_sd(c)		((c)->type == MMC_TYPE_SD)
 #define mmc_card_sdio(c)	((c)->type == MMC_TYPE_SDIO)
diff --git a/include/linux/mmc/core.h b/include/linux/mmc/core.h
index 29aa50711626..21dcd79f8f0e 100644
--- a/include/linux/mmc/core.h
+++ b/include/linux/mmc/core.h
@@ -166,6 +166,10 @@ struct mmc_request {
 
 struct mmc_card;
 
+#ifdef CONFIG_MMC_PSTORE
+extern void mmc_wait_for_pstore_req(struct mmc_host *, struct mmc_request *);
+#endif /* CONFIG_MMC_PSTORE */
+
 void mmc_wait_for_req(struct mmc_host *host, struct mmc_request *mrq);
 int mmc_wait_for_cmd(struct mmc_host *host, struct mmc_command *cmd,
 		int retries);
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index c079b932330f..ef57313ee3ea 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -173,6 +173,12 @@ struct mmc_host_ops {
 	 */
 	int	(*multi_io_quirk)(struct mmc_card *card,
 				  unsigned int direction, int blk_size);
+
+#ifdef CONFIG_MMC_PSTORE
+	void	(*req_cleanup_pending)(struct mmc_host *host);
+	int	(*req_completion_poll)(struct mmc_host *host,
+					unsigned long timeout);
+#endif
 };
 
 struct mmc_cqe_ops {
-- 
2.17.1