atmel-mci: support multiple mmc slots
The Atmel MCI controller can drive multiple cards through separate sets
of pins, but only one at a time. This patch adds support for
multiplexing access to the controller so that multiple card slots can be
used as if they were hooked up to separate mmc controllers.
The atmel-mci driver registers each slot as a separate mmc_host. Both
access the same common controller state, but they also have some state
on their own for card detection/write protect handling, and separate
shadows of the MR and SDCR registers.
When one of the slots receives a request from the mmc core, the common
controller state is checked. If it's idle, the request is submitted
immediately. If not, the request is added to a queue. When a request is
done, the queue is checked and if there is a queued request, it is
submitted before the completion callback is called.
This patch also includes a few cleanups and fixes, including a locking
overhaul. I had to change the locking extensively in any case, so I
might as well try to get it right. The driver no longer takes any
irq-safe locks, which may or may not improve the overall system
performance.
This patch also adds a bit of documentation of the internal data
structures.
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>
diff --git a/arch/avr32/include/asm/atmel-mci.h b/arch/avr32/include/asm/atmel-mci.h
index d38c64c..5d5ae12 100644
--- a/arch/avr32/include/asm/atmel-mci.h
+++ b/arch/avr32/include/asm/atmel-mci.h
@@ -1,6 +1,8 @@
#ifndef __ASM_AVR32_ATMEL_MCI_H
#define __ASM_AVR32_ATMEL_MCI_H
+#define ATMEL_MCI_MAX_NR_SLOTS 2
+
/**
* struct mci_slot_pdata - board-specific per-slot configuration
* @bus_width: Number of data lines wired up the slot
@@ -11,6 +13,10 @@
* set to 0. The other fields are ignored in this case.
*
* Any pins that aren't available should be set to a negative value.
+ *
+ * Note that support for multiple slots is experimental -- some cards
+ * might get upset if we don't get the clock management exactly right.
+ * But in most cases, it should work just fine.
*/
struct mci_slot_pdata {
unsigned int bus_width;
@@ -23,7 +29,7 @@
* @slot: Per-slot configuration data.
*/
struct mci_platform_data {
- struct mci_slot_pdata slot[2];
+ struct mci_slot_pdata slot[ATMEL_MCI_MAX_NR_SLOTS];
};
#endif /* __ASM_AVR32_ATMEL_MCI_H */