usb: dwc3: switch trb enqueue/dequeue and first_trb_index to u8

We *know* that we have 1 PAGE (4096 bytes) for our
TRB poll. We also know the size of each TRB and know
that we can fit 256 of them in one PAGE. By using a
u8 type we can make sure that:

	enqueue++ % 256;

gets optimized to an increment only.

Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index c0049c8..2f19573 100644 (file)
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -470,8 +470,6 @@ struct dwc3_ep {
 
        struct dwc3_trb         *trb_pool;
        dma_addr_t              trb_pool_dma;
-       u32                     trb_enqueue;
-       u32                     trb_dequeue;
        const struct usb_ss_ep_comp_descriptor *comp_desc;
        struct dwc3             *dwc;
 
@@ -487,6 +485,18 @@ struct dwc3_ep {
        /* This last one is specific to EP0 */
 #define DWC3_EP0_DIR_IN                (1 << 31)
 
+       /*
+        * IMPORTANT: we *know* we have 256 TRBs in our @trb_pool, so we will
+        * use a u8 type here. If anybody decides to increase number of TRBs to
+        * anything larger than 256 - I can't see why people would want to do
+        * this though - then this type needs to be changed.
+        *
+        * By using u8 types we ensure that our % operator when incrementing
+        * enqueue and dequeue get optimized away by the compiler.
+        */
+       u8                      trb_enqueue;
+       u8                      trb_dequeue;
+
        u8                      number;
        u8                      type;
        u8                      resource_index;
@@ -641,8 +651,8 @@ struct dwc3_request {
        struct usb_request      request;
        struct list_head        list;
        struct dwc3_ep          *dep;
-       u32                     first_trb_index;
 
+       u8                      first_trb_index;
        u8                      epnum;
        struct dwc3_trb         *trb;
        dma_addr_t              trb_dma;