mmc: dw_mmc: Add data CRC error injection

This driver has had problems when handling data errors. Add fault
injection support so that the abort handling can be easily triggered and
regression-tested. A hrtimer is used to indicate a data CRC error at
various points during the data transfer.

Note that for the recent problem with hangs in the case of some data CRC
errors, a udelay(10) inserted at the start of send_stop_abort() greatly
helped in triggering the error, but I've not included this as part of
the fault injection support since it seemed too specific.

Signed-off-by: Vincent Whitchurch <[e-mail]>
Reviewed-by: Jaehoon Chung <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Ulf Hansson <[e-mail]>

drivers/mmc/host/dw_mmc.c

···
 #include <linux/interrupt.h>
 #include <linux/iopoll.h>
 #include <linux/ioport.h>
+#include <linux/ktime.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/prandom.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/stat.h>
···
 			   &host->pending_events);
 	debugfs_create_xul("completed_events", S_IRUSR, root,
 			   &host->completed_events);
+#ifdef CONFIG_FAULT_INJECTION
+	fault_create_debugfs_attr("fail_data_crc", root, &host->fail_data_crc);
+#endif
 }
 #endif /* defined(CONFIG_DEBUG_FS) */
 
···
 	.prepare_hs400_tuning	= dw_mci_prepare_hs400_tuning,
 };
 
+#ifdef CONFIG_FAULT_INJECTION
+static enum hrtimer_restart dw_mci_fault_timer(struct hrtimer *t)
+{
+	struct dw_mci *host = container_of(t, struct dw_mci, fault_timer);
+	unsigned long flags;
+
+	spin_lock_irqsave(&host->irq_lock, flags);
+
+	if (!host->data_status)
+		host->data_status = SDMMC_INT_DCRC;
+	set_bit(EVENT_DATA_ERROR, &host->pending_events);
+	tasklet_schedule(&host->tasklet);
+
+	spin_unlock_irqrestore(&host->irq_lock, flags);
+
+	return HRTIMER_NORESTART;
+}
+
+static void dw_mci_start_fault_timer(struct dw_mci *host)
+{
+	struct mmc_data *data = host->data;
+
+	if (!data || data->blocks <= 1)
+		return;
+
+	if (!should_fail(&host->fail_data_crc, 1))
+		return;
+
+	/*
+	 * Try to inject the error at random points during the data transfer.
+	 */
+	hrtimer_start(&host->fault_timer,
+		      ms_to_ktime(prandom_u32() % 25),
+		      HRTIMER_MODE_REL);
+}
+
+static void dw_mci_stop_fault_timer(struct dw_mci *host)
+{
+	hrtimer_cancel(&host->fault_timer);
+}
+
+static void dw_mci_init_fault(struct dw_mci *host)
+{
+	host->fail_data_crc = (struct fault_attr) FAULT_ATTR_INITIALIZER;
+
+	hrtimer_init(&host->fault_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+	host->fault_timer.function = dw_mci_fault_timer;
+}
+#else
+static void dw_mci_init_fault(struct dw_mci *host)
+{
+}
+
+static void dw_mci_start_fault_timer(struct dw_mci *host)
+{
+}
+
+static void dw_mci_stop_fault_timer(struct dw_mci *host)
+{
+}
+#endif
+
 static void dw_mci_request_end(struct dw_mci *host, struct mmc_request *mrq)
 	__releases(&host->lock)
 	__acquires(&host->lock)
···
 				break;
 			}
 
+			dw_mci_stop_fault_timer(host);
 			host->data = NULL;
 			set_bit(EVENT_DATA_COMPLETE, &host->completed_events);
 			err = dw_mci_data_complete(host, data);
···
 			if (mrq->cmd->error && mrq->data)
 				dw_mci_reset(host);
 
+			dw_mci_stop_fault_timer(host);
 			host->cmd = NULL;
 			host->data = NULL;
 
···
 
 	set_bit(EVENT_CMD_COMPLETE, &host->pending_events);
 	tasklet_schedule(&host->tasklet);
+
+	dw_mci_start_fault_timer(host);
 }
 
 static void dw_mci_handle_cd(struct dw_mci *host)
···
 	spin_lock_init(&host->lock);
 	spin_lock_init(&host->irq_lock);
 	INIT_LIST_HEAD(&host->queue);
+
+	dw_mci_init_fault(host);
 
 	/*
 	 * Get the host data width - this assumes that HCON has been set with

drivers/mmc/host/dw_mmc.h

···
 #include <linux/mmc/core.h>
 #include <linux/dmaengine.h>
 #include <linux/reset.h>
+#include <linux/fault-inject.h>
+#include <linux/hrtimer.h>
 #include <linux/interrupt.h>
 
 enum dw_mci_state {
···
 	struct timer_list       cmd11_timer;
 	struct timer_list       cto_timer;
 	struct timer_list       dto_timer;
+
+#ifdef CONFIG_FAULT_INJECTION
+	struct fault_attr	fail_data_crc;
+	struct hrtimer		fault_timer;
+#endif
 };
 
 /* DMA ops for Internal/External DMAC interface */