usb: musb: ux500: optimize DMA callback routine

Skip the use of work queue and call musb_dma_completion() directly from
DMA callback context.

Here follows measurements on a Snowball board with ondemand governor active.

Performance using work queue:
(105 MB) copied, 6.23758 s, 16.8 MB/s
(105 MB) copied, 5.7151 s, 18.3 MB/s
(105 MB) copied, 5.83583 s, 18.0 MB/s
(105 MB) copied, 5.93611 s, 17.7 MB/s

Performance without work queue
(105 MB) copied, 5.62173 s, 18.7 MB/s
(105 MB) copied, 5.61811 s, 18.7 MB/s
(105 MB) copied, 5.57817 s, 18.8 MB/s
(105 MB) copied, 5.58549 s, 18.8 MB/s

Signed-off-by: Per Forlin <per.forlin@linaro.org>
Acked-by: Mian Yousaf Kaukab <mian.yousaf.kaukab@stericsson.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 3 insertions, 36 deletions

diff --git a/drivers/usb/musb/ux500_dma.c b/drivers/usb/musb/ux500_dma.c
index ef4333f4bbe0..a163632877af 100644
--- a/drivers/usb/musb/ux500_dma.c
+++ b/drivers/usb/musb/ux500_dma.c
@@ -37,7 +37,6 @@ struct ux500_dma_channel {
         struct dma_channel channel;
         struct ux500_dma_controller *controller;
         struct musb_hw_ep *hw_ep;
-        struct work_struct channel_work;
         struct dma_chan *dma_chan;
         unsigned int cur_len;
         dma_cookie_t cookie;
@@ -56,31 +55,11 @@ struct ux500_dma_controller {
         dma_addr_t phy_base;
 };
 
-/* Work function invoked from DMA callback to handle tx transfers. */
-static void ux500_tx_work(struct work_struct *data)
-{
-        struct ux500_dma_channel *ux500_channel = container_of(data,
-                struct ux500_dma_channel, channel_work);
-        struct musb_hw_ep       *hw_ep = ux500_channel->hw_ep;
-        struct musb *musb = hw_ep->musb;
-        unsigned long flags;
-
-        dev_dbg(musb->controller, "DMA tx transfer done on hw_ep=%d\n",
-                hw_ep->epnum);
-
-        spin_lock_irqsave(&musb->lock, flags);
-        ux500_channel->channel.actual_len = ux500_channel->cur_len;
-        ux500_channel->channel.status = MUSB_DMA_STATUS_FREE;
-        musb_dma_completion(musb, hw_ep->epnum,
-                                ux500_channel->is_tx);
-        spin_unlock_irqrestore(&musb->lock, flags);
-}
-
 /* Work function invoked from DMA callback to handle rx transfers. */
-static void ux500_rx_work(struct work_struct *data)
+void ux500_dma_callback(void *private_data)
 {
-        struct ux500_dma_channel *ux500_channel = container_of(data,
-                struct ux500_dma_channel, channel_work);
+        struct dma_channel *channel = private_data;
+        struct ux500_dma_channel *ux500_channel = channel->private_data;
         struct musb_hw_ep       *hw_ep = ux500_channel->hw_ep;
         struct musb *musb = hw_ep->musb;
         unsigned long flags;
@@ -94,14 +73,7 @@ static void ux500_rx_work(struct work_struct *data)
         musb_dma_completion(musb, hw_ep->epnum,
                 ux500_channel->is_tx);
         spin_unlock_irqrestore(&musb->lock, flags);
-}
-
-void ux500_dma_callback(void *private_data)
-{
-        struct dma_channel *channel = (struct dma_channel *)private_data;
-        struct ux500_dma_channel *ux500_channel = channel->private_data;
 
-        schedule_work(&ux500_channel->channel_work);
 }
 
 static bool ux500_configure_channel(struct dma_channel *channel,
@@ -330,7 +302,6 @@ static int ux500_dma_controller_start(struct dma_controller *c)
         void **param_array;
         struct ux500_dma_channel *channel_array;
         u32 ch_count;
-        void (*musb_channel_work)(struct work_struct *);
         dma_cap_mask_t mask;
 
         if ((data->num_rx_channels > UX500_MUSB_DMA_NUM_RX_CHANNELS) ||
@@ -347,7 +318,6 @@ static int ux500_dma_controller_start(struct dma_controller *c)
         channel_array = controller->rx_channel;
         ch_count = data->num_rx_channels;
         param_array = data->dma_rx_param_array;
-        musb_channel_work = ux500_rx_work;
 
         for (dir = 0; dir < 2; dir++) {
                 for (ch_num = 0; ch_num < ch_count; ch_num++) {
@@ -374,15 +344,12 @@ static int ux500_dma_controller_start(struct dma_controller *c)
                                 return -EBUSY;
                         }
 
-                        INIT_WORK(&ux500_channel->channel_work,
-                                musb_channel_work);
                 }
 
                 /* Prepare the loop for TX channels */
                 channel_array = controller->tx_channel;
                 ch_count = data->num_tx_channels;
                 param_array = data->dma_tx_param_array;
-                musb_channel_work = ux500_tx_work;
                 is_tx = 1;
         }