[PATCH 3/4] mmc: dw_mmc: Add desc_num field for clarity

[Shawn Lin]

The ring_size field in struct dw_mci is misleadingly named.
Despite its name, it does not represent the size of the descriptor
ring buffer in bytes, but rather the number of descriptors allocated
within the fixed-size ring buffer.

The actual ring buffer size is fixed at PAGE_SIZE (or DESC_RING_BUF_SZ,
which equals PAGE_SIZE). Within this buffer, we allocate either
struct idmac_desc or struct idmac_desc_64addr descriptors, and
ring_size stores the count of these descriptors.

This naming has caused confusion, as it's also used to set
mmc->max_segs (the maximum number of scatter-gather segments),
which logically corresponds to the number of descriptors, not a
size in bytes.

No functional change is introduced by this naming-only patch.

Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
---

 drivers/mmc/host/dw_mmc.c | 16 ++++++++--------
 drivers/mmc/host/dw_mmc.h |  2 ++
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 20193ee..df6daa6 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -491,12 +491,12 @@ static int dw_mci_idmac_init(struct dw_mci *host)
 
 	if (host->dma_64bit_address == 1) {
 		struct idmac_desc_64addr *p;
-		/* Number of descriptors in the ring buffer */
-		host->ring_size =
+
+		host->desc_num =
 			DESC_RING_BUF_SZ / sizeof(struct idmac_desc_64addr);
 
 		/* Forward link the descriptor list */
-		for (i = 0, p = host->sg_cpu; i < host->ring_size - 1;
+		for (i = 0, p = host->sg_cpu; i < host->desc_num - 1;
 								i++, p++) {
 			p->des6 = (host->sg_dma +
 					(sizeof(struct idmac_desc_64addr) *
@@ -519,13 +519,13 @@ static int dw_mci_idmac_init(struct dw_mci *host)
 
 	} else {
 		struct idmac_desc *p;
-		/* Number of descriptors in the ring buffer */
-		host->ring_size =
+
+		host->desc_num =
 			DESC_RING_BUF_SZ / sizeof(struct idmac_desc);
 
 		/* Forward link the descriptor list */
 		for (i = 0, p = host->sg_cpu;
-		     i < host->ring_size - 1;
+		     i < host->desc_num - 1;
 		     i++, p++) {
 			p->des3 = cpu_to_le32(host->sg_dma +
 					(sizeof(struct idmac_desc) * (i + 1)));
@@ -2858,10 +2858,10 @@ static int dw_mci_init_host(struct dw_mci *host)
 
 	/* Useful defaults if platform data is unset. */
 	if (host->use_dma == TRANS_MODE_IDMAC) {
-		mmc->max_segs = host->ring_size;
+		mmc->max_segs = host->desc_num;
 		mmc->max_blk_size = 65535;
 		mmc->max_seg_size = 0x1000;
-		mmc->max_req_size = mmc->max_seg_size * host->ring_size;
+		mmc->max_req_size = mmc->max_seg_size * host->desc_num;
 		mmc->max_blk_count = mmc->max_req_size / 512;
 	} else if (host->use_dma == TRANS_MODE_EDMAC) {
 		mmc->max_segs = 64;
diff --git a/drivers/mmc/host/dw_mmc.h b/drivers/mmc/host/dw_mmc.h
index 14fb2b3..a05100c 100644
--- a/drivers/mmc/host/dw_mmc.h
+++ b/drivers/mmc/host/dw_mmc.h
@@ -80,6 +80,7 @@ struct dw_mci_dma_slave {
  * @cmd_status: Snapshot of SR taken upon completion of the current
  *	command. Only valid when EVENT_CMD_COMPLETE is pending.
  * @ring_size: Buffer size for idma descriptors.
+ * @desc_num: Number of idmac descriptors available.
  * @dms: structure of slave-dma private data.
  * @phy_regs: physical address of controller's register map
  * @data_status: Snapshot of SR taken upon completion of the current
@@ -185,6 +186,7 @@ struct dw_mci {
 	const struct dw_mci_dma_ops	*dma_ops;
 	/* For idmac */
 	unsigned int		ring_size;
+	unsigned short		desc_num;
 
 	/* For edmac */
 	struct dw_mci_dma_slave *dms;
-- 
2.7.4