Commit graph

11608 commits

Author SHA1 Message Date
Maxime Ripard
c163668a4a usb: gadget: Move USBNET_HOST_ADDR to Kconfig
While the USB Ethernet device address is already defined in Kconfig, the
host address isn't. Convert it.

Reviewed-by: Łukasz Majewski <lukma@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
2017-10-03 19:12:04 +02:00
Maxime Ripard
74e7997c70 usb: gadget: Document USBNET_DEVADDR
Add an help about the USBNET_DEVADDR Kconfig option to make it clearer what
it's about.

Acked-by: Łukasz Majewski <lukma@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
2017-10-03 19:12:04 +02:00
Maxime Ripard
5506ff149d usb: gadget: Move USBNET_DEVADDR option out of g_dnl
The USBNET_DEVADDR has nothing to do with the USB download gadget, but
rather with the USB Ethernet gadget. Move it out of the if statement.

Acked-by: Łukasz Majewski <lukma@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
2017-10-03 19:12:04 +02:00
Tom Rini
4d1c166fee Merge git://git.denx.de/u-boot-usb 2017-10-01 18:06:53 -04:00
Masahiro Yamada
dc04b35ef2 usb: dwc3: add UniPhier specific glue layer
Add UniPhier platform specific glue layer to support USB3 Host mode
on Synopsys DWC3 IP.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Marek Vasut <marex@denx.de>
2017-10-01 16:32:55 +02:00
Bin Meng
fae35857e1 usb: xhci: Set 'Average TRB Length' to 8 for control endpoints
Update the codes to conform with xHCI spec chapter 6.2.3.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:55 +02:00
Bin Meng
ab2b727dc0 usb: xhci: Set 'Error Count' to 0 for isoch endpoints
Per xHCI spec, 'Error Count' should be set to 0 for isoch endpoints.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:54 +02:00
Bin Meng
fa483b2c75 usb: xhci: Program max burst size for endpoint
The 'Max Burst Size' indicates to the xHC the maximum number of
consecutive USB transactions that should be executed per scheduling
opportunity. This is a “zero-based” value, where 0 to 15 represents
burst sizes of 1 to 16, but at present this is always set to zero.
Let's program the required value according to real needs.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:54 +02:00
Bin Meng
f51966bf7a usb: xhci: Honor endpoint's interval
USB endpoint reports the period between consecutive requests to send
or receive data as bInverval in its endpoint descriptor. So far this
is ignored by xHCI driver and the 'Interval' field in xHC's endpoint
context is always programmed to zero which means 1ms for low speed
or full speed , or 125us for high speed or super speed. We should
honor the interval by getting it from endpoint descriptor.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:54 +02:00
Bin Meng
b5aa857b95 usb: xhci: Fix max packet size for full speed device endpoint 0
In xhci_check_maxpacket(), the control endpoint 0 max packet size
is wrongly taken from the interface's endpoint descriptor. However
the default endpoint 0 does not come with an endpoint descriptor
hence is not included in the interface structure. Change to use
epmaxpacketin[0] instead.

The other bug in this routine is that when setting max packet size
to the xHC endpoint 0 context, it does not clear its previous value
at all before programming a new one.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:54 +02:00
Bin Meng
1897d60130 usb: xhci: Add interrupt transfer support
xHCI uses normal TRBs for both bulk and interrupt. This adds the
missing interrupt transfer support to xHCI so that devices like
USB keyboard that uses interrupt transfer can work.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:53 +02:00
Bin Meng
8a0e6d8307 usb: xhci: Don't assume LS/FS devices are always behind a HS hub
At present xHCI driver assumes LS/FS devices are attached directly
to a HS hub. If they are connected to a LS/FS hub, the driver will
fail to perform the USB enumeration process on such devices.

This is fixed by looking from the device itself all the way up to
the HS hub where the TT that serves the device is located.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:52 +02:00
Bin Meng
ad56e4b684 dm: usb: emul: Drop usb_emul_reset()
With the root hub unbinding in usb_stop(), there is no need to do
a Sandbox-specific reset operation. usb_emul_reset() is no longer
used anywhere, drop it.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:51 +02:00
Bin Meng
ad0a9378bf dm: usb: Remove no longer needed blk_unbind_all()
With the root hub unbinding in usb_stop(), there is no need to do
a blk uclass specific unbind operation.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:51 +02:00
Bin Meng
d4efefe32e dm: usb: Fix broken usb_stop()
At present we only do device_remove() during usb stop. The DM API
device_remove() only marks the device state as inactivated, but
still keeps its USB topology (eg: parent, children, etc) in the DM
device structure. There is no issue if we only start USB subsystem
once and never stop it. But a big issue occurs when we do 'usb stop'
and 'usb start' multiple times.

Strange things may be observed with current implementation, like:
- the enumeration may report only 1 mass storage device is detected,
  but the total number of USB devices is correct.
- USB keyboard does not work anymore after a bunch of 'usb reset'
  even if 'usb tree' shows it is correctly identified.
- read/write flash drive via 'fatload usb' may complain "Bad device"

In fact, every time when USB host controller starts the enumeration
process, it takes random time for each USB port to show up online,
hence each USB device may appear in a different order from previous
enumeration, and gets assigned to a totally different USB address.
As a result, we end up using a stale USB topology in the DM device
structure which still reflects the previous enumeration result, and
it may create an exact same DM device name like generic_bus_0_dev_7
that is already in the DM device structure. And since the DM device
structure is there, there is no device_bind() call to bind driver to
the device during current enumeration process, eventually creating
an inconsistent software representation of the hardware topology, a
non-working USB subsystem.

The fix is to clear the unused USB topology in the usb_stop(), by
calling device_unbind() on each controller's root hub device, and
the unbinding will unbind all of its children automatically.

For Sandbox, we need scan the device tree each time when we start
the USB stack, in order to re-create the emulated USB devices and
bind drivers for them before we actually do the driver probe.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:51 +02:00
Bin Meng
d7771f0c5c usb: emul: hub: Report the actual device speed of the emulation device
At present the usb hub emulator always reports its downstream port
speed as full speed. Actually it is high speed for sandbox-flash,
and low speed for sandbox-keyb. We can determine the device speed
by checking its device descriptor bcdUSB field, and do the proper
hub port status report based on that.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:51 +02:00
Bin Meng
848436a48d usb: emul: Expose find_descriptor() as a public API
This can be useful outside of the sandbox usb emulation uclass
driver. Expose it as a public API with a proper prefix (usb_emul_).

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:51 +02:00
Bin Meng
84aa8536f0 usb: sandbox: Fix emulator device select logic in usb_emul_find_devnum()
Current emulator select logic in usb_emul_find_devnum() is to test
the USB address. The USB address of the device being enumerated is
initialized to zero at the beginning of the enumeration process in
usb_setup_device(). At this point, the saved USB address in the
platform data has not been assigned to any valid USB address either.
This means: the logic will select an emulator device according to
its sequence of declaring order in the device tree. Take test.dts
for example, flash-stick@0 will be selected before flash-stick@1.
But unfortunately such logic is wrong.

In fact USB devices show up in a random order during the enumeration
which means usb_emul_find_devnum() may be called on port 3 for keyb@3
before on port 0 for flash-stick@0.

To fix this, we introduce a new emulator uclass specific platdata
to store the USB device's port number on its parent hub, and update
the logic to test the port number instead.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:50 +02:00
Bin Meng
813f74ea47 usb: sandbox: Initialize root hub's device speed to high speed
At present 'usb tree' shows that the root hub on the Sandbox USB
controller is at full speed. But its device descriptor says it's
USB 2.0, so let's report it as a high speed device.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:50 +02:00
Bin Meng
98b639fc50 usb: emul: Remove maxpacketsize in usb_emul_setup_device()
This parameter is never used.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-10-01 16:32:50 +02:00
Philipp Tomsich
9086eab8fe power: spl: add SPL_DM_REGULATOR_FIXED in Kconfig
The Makefile already tests for SPL_DM_REGULATOR_FIXED, but Kconfig
does not provide it.  This adds SPL_DM_REGULATOR_FIXED to Kconfig.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2017-10-01 00:33:35 +02:00
Elaine Zhang
be93fc2476 rockchip: i2c: rk3328: support i2c for rk3328 SoC
Add compatible to support rk3328 i2c

Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Heiko Schocher<hs@denx.de>
2017-10-01 00:33:33 +02:00
Philipp Tomsich
fd0a1ba52e rockchip: pinctrl: rk3368: add pinctrl for SDMMC0
Apparently, our earlier assumption that the BROM will always set up
the iomux for SDcard communication does not always hold true: when
booting U-Boot from the on-module (on the RK3368-uQ7) eMMC, the SDcard
pins are not set up and need to be configured by the pinctrl driver to
allow SD card access.

This change implements support for setting up the SDMMC pins in
pinctrl for the RK3368.

Reported-by: Klaus Goger <klaus.goger@theobroma-systems.com>
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2017-10-01 00:33:33 +02:00
Kever Yang
f3f6591ca3 rockchip: rk322x: fix pd_bus hclk/pclk
The pd_bus hclk/pclk source is pd_bus aclk, not the PLL.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:32 +02:00
Kever Yang
21c7acc7cb rockchip: clk: fix typo in rk322x clock driver
Fix typo RK322X/RK3036 in rk322x clock driver.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:32 +02:00
Kever Yang
a27290a6f8 rockchip: rk3188: ram: add support for 16bit row address
RK3188 using the same ddr_conf for both 15 bit and 16 bit row address.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
[Fixed compile-error by declaring 'row':]
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:32 +02:00
Kever Yang
0176399b79 rockchip: rk322x: add sdram driver
Add driver for rk322x to support sdram initialize in SPL.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:32 +02:00
Kever Yang
f0768491db rockchip: rk3328: move sdram driver to driver/ram
Since we have CONFIG_RAM framwork and its driver folder, move the driver
into it.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:31 +02:00
Kever Yang
c9eb7bca4b rockchip: rk3288: move sdram driver to driver/ram
Since we have CONFIG_RAM framwork and its driver folder, move the driver
into it.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:31 +02:00
Kever Yang
5b67d7010b rockchip: rk3188: move sdram driver to driver/ram
Since we have CONFIG_RAM framwork and its driver folder, move the driver
into it.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:31 +02:00
Kever Yang
b5934cf67c rockchip: rk3399: move sdram driver to driver/ram
Since we have CONFIG_RAM framwork and its driver folder, move the driver
into it.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:31 +02:00
David Wu
364fc7315a rockchip: clk: Add rk3399 SARADC clock support
The clk_saradc is dividing from the 24M, clk_saradc=24MHz/(saradc_div_con+1).
SARADC integer divider control register is 8-bits width.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:30 +02:00
David Wu
615514c16d rockchip: clk: Add rk3368 SARADC clock support
The clk_saradc is dividing from the 24M, clk_saradc=24MHz/(saradc_div_con+1).
SARADC integer divider control register is 8-bits width.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:30 +02:00
David Wu
b375d84135 rockchip: clk: Add rk3328 SARADC clock support
The clk_saradc is dividing from the 24M, clk_saradc=24MHz/(saradc_div_con+1).
SARADC integer divider control register is 10-bits width.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:30 +02:00
David Wu
ef4cf5ae39 rockchip: clk: Add SARADC clock support for rk3288
The clk_saradc is dividing from the 24M, clk_saradc=24MHz/(saradc_div_con+1).
SARADC integer divider control register is 8-bits width.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:29 +02:00
David Wu
2e4ce50d1a rockchip: clk: Add rv1108 SARADC clock support
The clk_saradc is dividing from the 24M, clk_saradc=24MHz/(saradc_div_con+1).
SARADC integer divider control register is 10-bits width.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:29 +02:00
David Wu
ae3ed042ed dm: adc: Add driver for Rockchip SARADC
The ADC can support some channels signal-ended some bits Successive Approximation
Register (SAR) A/D Converter, like 6-channel and 10-bit. It converts the analog
input signal into some bits binary digital codes.

Signed-off-by: David Wu <david.wu@rock-chips.com>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-10-01 00:33:29 +02:00
Patrice Chotard
0cc40dfc66 dm: clk: add missing .priv_auto_alloc_size() for stm32f7
Add missing .priv_auto_alloc_size() callback.
Previously private struct stm32_clk was not allocate
which leads to unpredictable behaviour

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2017-09-29 14:07:57 -04:00
Adam Ford
ab0ac27242 spi: davinci_spi: Add da830-spi support for DM
The DM support is already in the driver, so add
da830-spi to the compatible list.

Reviewed-by: Jagan Teki <jagan@openedev.com>
Signed-off-by: Adam Ford <aford173@gmail.com>
2017-09-29 10:52:20 -04:00
Masahiro Yamada
3d3108d459 mmc: sdhci-cadence: set timing mode register depending on frequency
The MMC framework in U-Boot does not support a systematic API for
timing switch like mmc_set_timing() in Linux.

U-Boot just provides a hook to change the clock frequency via
mmc_set_clock().  It is up to drivers if additional register
settings are needed.

This driver needs to set a correct timing mode into a register when
it migrates to a different speed mode.  Only increasing clock frequency
could result in setup/hold timing violation.

The timing mode should be decided by checking MMC_TIMING_* like
drivers/mmc/host/sdhci-cadence.c in Linux, but "timing" is not
supported by U-Boot for now.  Just use mmc->clock to decide the
timing mode.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-09-29 11:34:22 +09:00
Marek Vasut
9f13021f81 mmc: uniphier-sd: Add vqmmc regulator support
Add initial support for setting the vqmmc regulator. Since we do not
support 1V8 modes, set the regulator to 3V3 and enable it.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-09-29 11:17:29 +09:00
Marek Vasut
d6c40031d5 mmc: uniphier-sd: Update the file to match V3 patchset
Old version of the uniphier-sd 64bit IO support patchset V1 was
applied by the maintainer, update the uniphier-sd.c with the
changes from the V3 of the patchset.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2017-09-29 11:14:14 +09:00
Patrice Chotard
b312c590bc mmc: Add MMC support for stm32h7 Socs
This patch adds SD/MMC support for STM32H7 SoCs.

Here is an extraction of SDMMC main features, embedded in
STM32H7 SoCs.
The SD/MMC block include the following:
 _ Full compliance with MultiMediaCard System Specification
   Version 4.51. Card support for three different databus modes:
   1-bit (default), 4-bit and 8-bit.
 _ Full compatibility with previous versions of MultiMediaCards
   (backward compatibility).
 _ Full compliance with SD memory card specifications version 4.1.
   (SDR104 SDMMC_CK speed limited to maximum allowed IO speed,
    SPI mode and UHS-II mode not supported).
 _ Full compliance with SDIO card specification version 4.0.
   Card support for two different databus modes: 1-bit (default)
   and 4-bit. (SDR104 SDMMC_CK speed limited to maximum allowed IO
   speed, SPI mode and UHS-II mode not supported).
 _ Data transfer up to 208 Mbyte/s for the 8 bit mode.
   (depending maximum allowed IO speed).
 _ Data and command output enable signals to control external
   bidirectional drivers.

The current version of the SDMMC supports only one SD/SDIO/MMC card
at any one time and a stack of MMC Version 4.51 or previous.

Signed-off-by: Christophe Kerello <christophe.kerello@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
2017-09-28 20:23:19 +09:00
Seung-Woo Kim
a939af0c74 usb: dwc2: Align size of invalidating dcache before starting DMA
During using dwc2 usb gadget, if usb message size is too small,
following cache misaligned warning is shown:

   CACHE: Misaligned operation at range [bfdbcb00, bfdbcb04]

Align size of invalidating dcache before starting DMA to remove the
warning.

Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
2017-09-27 12:12:23 +02:00
Bin Meng
2e5026a2f0 usb: kbd: Set a default polling mechanism for USB keyboard
The choice of "USB keyboard polling" cannot be optional as without
one mechanism being set, it just doesn't work. Set the default one
to CONFIG_SYS_USB_EVENT_POLL.

Fixes: ecad7051 ("configs: Migrate all of the existing USB symbols, except fastboot")
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-09-27 12:12:23 +02:00
Philipp Tomsich
6e652e3a7d usb: host: ehci-generic: convert to livetree
Update the generic EHCI driver to support a live tree.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-09-27 12:12:23 +02:00
Philipp Tomsich
a9d3037a8e usb: dwc2: convert to livetree
Update the DWC2 USB driver to support a live tree.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-09-27 12:12:22 +02:00
Philipp Tomsich
32c8eee37f rockchip: xhci: Convert to livetree
Update the Rockchip xhci wrapper driver to support a live device tree.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
2017-09-27 12:12:22 +02:00
Bin Meng
a23aa66baa dm: usb: ehci: Implement get_max_xfer_size() operation
EHCD can handle any transfer length as long as there is enough free
heap space left, hence set the theoretical max number SIZE_MAX.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-09-27 12:12:22 +02:00
Bin Meng
022ceacaf8 dm: usb: xhci: Implement get_max_xfer_size() operation
xHCD allocates one segment which includes 64 TRBs for each endpoint
and the last TRB in this segment is configured as a link TRB to form
a TRB ring. Each TRB can transfer up to 64K bytes, however data
buffers referenced by transfer TRBs shall not span 64KB boundaries.
Hence the maximum number of TRBs we can use in one transfer is 62.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
2017-09-27 12:12:22 +02:00