[PATCH] usb: musb: cppi41: fix not transmitting zero length packet issue

[Bin Liu]

CPPI TX does not transmit ZLP for TX transfers which
- transfer size is multiple of EP packet size,
- and URB_ZERO_PACKET is set in urb->transfer_flags.

The fix is transmitting the ZLP using PIO mode after the CPPI TX is
done.

Validated using the following usbtest write case for MUSB host mode.

  # testusb -t1 -c1

Signed-off-by: Bin Liu <b-...@ti.com>
---
 drivers/usb/musb/musb_cppi41.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
index 5989def..e9a0e54 100644
--- a/drivers/usb/musb/musb_cppi41.c
+++ b/drivers/usb/musb/musb_cppi41.c
@@ -39,6 +39,7 @@ struct cppi41_dma_channel {
        u32 transferred;
        u32 packet_sz;
        struct list_head tx_check;
+       u32 tx_zlp;
 };
 
 #define MUSB_DMA_NUM_CHANNELS 15
@@ -122,6 +123,8 @@ static void cppi41_trans_done(struct cppi41_dma_channel 
*cppi41_channel)
 {
        struct musb_hw_ep *hw_ep = cppi41_channel->hw_ep;
        struct musb *musb = hw_ep->musb;
+       void __iomem *epio = hw_ep->regs;
+       u16 csr;
 
        if (!cppi41_channel->prog_len) {
 
@@ -130,15 +133,22 @@ static void cppi41_trans_done(struct cppi41_dma_channel 
*cppi41_channel)
                        cppi41_channel->transferred;
                cppi41_channel->channel.status = MUSB_DMA_STATUS_FREE;
                cppi41_channel->channel.rx_packet_done = true;
+
+               /* transmit ZLP using PIO mode for transfers which size is
+                * multiple of EP packet size. */
+               if (cppi41_channel->tx_zlp && (cppi41_channel->transferred %
+                                       cppi41_channel->packet_sz) == 0) {
+                       musb_ep_select(musb->mregs, hw_ep->epnum);
+                       csr = MUSB_TXCSR_MODE | MUSB_TXCSR_TXPKTRDY;
+                       musb_writew(epio, MUSB_TXCSR, csr);
+               }
                musb_dma_completion(musb, hw_ep->epnum, cppi41_channel->is_tx);
        } else {
                /* next iteration, reload */
                struct dma_chan *dc = cppi41_channel->dc;
                struct dma_async_tx_descriptor *dma_desc;
                enum dma_transfer_direction direction;
-               u16 csr;
                u32 remain_bytes;
-               void __iomem *epio = cppi41_channel->hw_ep->regs;
 
                cppi41_channel->buf_addr += cppi41_channel->packet_sz;
 
@@ -362,6 +372,7 @@ static bool cppi41_configure_channel(struct dma_channel 
*channel,
        cppi41_channel->total_len = len;
        cppi41_channel->transferred = 0;
        cppi41_channel->packet_sz = packet_sz;
+       cppi41_channel->tx_zlp = (cppi41_channel->is_tx && mode) ? 1 : 0;
 
        /*
         * Due to AM335x' Advisory 1.0.13 we are not allowed to transfer more
-- 
1.8.4

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