Sansa Connect: Disable endpoint double buffering

Disabling double buffering results in expected CPPI TX behaviour. With
the double buffering enabled, sending single ZLP resulted in two ZLPs
being available. The two ZLPs is problematic because this causes Windows
to reset USB device after failed SCSI command.

The problematic sequence on Windows 10 was as follows:
  * Host sends SCSI Mode Sense(6) Informational Exceptions Control(0x1C)
  * Device sends ZLP
  * Device sends command failed response

With endpoint double buffering enabled the ZLP was read twice by host.
As host was expecting command response on the second read (and got ZLP
instead), host attempts recovery by resetting USB device and retrying.

Change-Id: I64e95998f429ffb7b14143d956b1f29d20218d14

1 files changed, 8 insertions, 2 deletions

diff --git a/firmware/target/arm/tms320dm320/sansa-connect/tnetv105_usb_drv.c b/firmware/target/arm/tms320dm320/sansa-connect/tnetv105_usb_drv.c
index 00c9c2b80d..5563a40814 100644
--- a/firmware/target/arm/tms320dm320/sansa-connect/tnetv105_usb_drv.c
+++ b/firmware/target/arm/tms320dm320/sansa-connect/tnetv105_usb_drv.c
@@ -393,12 +393,18 @@ static void tnetv_init_endpoints(void)
         epCfg.val = tnetv_usb_reg_read(TNETV_USB_EPx_CFG(epn));
         epStartAddr.val = tnetv_usb_reg_read(TNETV_USB_EPx_ADR(epn));
 
-        epCfg.f.in_dbl_buf = 1;
+        /* Linux kernel enables dbl buf for both IN and OUT.
+         * For IN this is problematic when tnetv_cppi_send() is called
+         * to send single ZLP, it will actually send two ZLPs.
+         * Disable the dbl buf here as datasheet is not available and
+         * this results in working mass storage on Windows 10.
+         */
+        epCfg.f.in_dbl_buf = 0;
         epCfg.f.in_toggle_rst = 1;
         epCfg.f.in_ack_int = 0;
         epCfg.f.in_stall = 0;
         epCfg.f.in_nak_int = 0;
-        epCfg.f.out_dbl_buf = 1;
+        epCfg.f.out_dbl_buf = 0;
         epCfg.f.out_toggle_rst = 1;
         epCfg.f.out_ack_int = 0;
         epCfg.f.out_stall = 0;