mmc: Support kmsg dumper based on pstore/blk

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@marvell.com>

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.

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

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);
 

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

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