When dma->start is failed,then it has to fall back to PIO mode
for current transfer.
But Host controller was already set to bits relevant to DMA operation.
If needs to use the PIO mode, Host controller has to stop the DMA
operation. (It's more stable than now.)
When it occurred error, it's not running any request.
Fixes: 3fc7eaef44 ("mmc: dw_mmc: Add external dma interface support")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Cc: <stable@vger.kernel.org> # v4.3+
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Since commit 87a18a6a56 ("mmc: mmc: Use ->card_busy() to detect busy
cards in __mmc_switch()") the ESDHC driver is broken:
mmc0: Card stuck in programming state! __mmc_switch
mmc0: error -110 whilst initialising MMC card
Since this commit __mmc_switch() uses ->card_busy(), which is
sdhci_card_busy() for the esdhc driver. sdhci_card_busy() uses the
PRESENT_STATE register, specifically the DAT0 signal level bit. But the
ESDHC uses a non-conformant PRESENT_STATE register, thus a read fixup is
required to make the driver work again.
Signed-off-by: Michael Walle <michael@walle.cc>
Fixes: 87a18a6a56 ("mmc: mmc: Use ->card_busy() to detect busy cards in __mmc_switch()")
Acked-by: Yangbo Lu <yangbo.lu@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: <stable@vger.kernel.org> # v4.8+
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
An interrupt may occur right after devm_request_irq() is called and
prior to the spinlock initialization, leading to a kernel oops,
as the interrupt handler uses the spinlock.
In order to prevent this problem, move the spinlock initialization
prior to requesting the interrupts.
Fixes: e4243f13d1 (mmc: mxs-mmc: add mmc host driver for i.MX23/28)
Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
In the eMMC 4.51 version of the spec, an EXT_CSD field called
GENERIC_CMD6_TIME[248] was added. This allows cards to specify the maximum
time it may need to move out from its busy state, when a CMD6 command has
been sent.
In cases when the card is compliant to versions < 4.51 of the eMMC spec,
obviously the core needs to use a fall-back value for this timeout, which
currently is set to 10 minutes. This value is completely in the wrong range
and importantly in some cases it causes a card initialization to take more
than 10 minute to complete.
Earlier this scenario was avoided as the mmc core used CMD13 to poll the
card, to find out when it stopped signaling busy. Commit 08573eaf1a
("mmc: mmc: do not use CMD13 to get status after speed mode switch")
changed this behavior.
Instead of reverting that commit, which would cause other issues, let's
instead start by picking a simple solution for the problem, by using a
500ms default generic CMD6 timeout.
The reason for using exactly 500ms, comes from observations that shows it's
quite common for cards to specify 250ms. 500ms is two times that value so
likely it should be enough for most cards.
Cc: <stable@vger.kernel.org> # v4.8+
Fixes: 08573eaf1a ("mmc: mmc: do not use CMD13 to get status after speed
mode switch")
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Stephen Boyd <sboyd@codeaurora.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
mmc_test_check_result_async() requires that struct mmc_async_req is
contained within struct mmc_test_async_req. Fix the "Commands during
non-blocking write" tests so that is the case.
Fixes: 4bbb9aac9a ("mmc: mmc_test: Add tests for sending commands during transfer")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Ritesh Harjani <riteshh@codeaurora.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
To prevent subsequent commands failing, ensure the cmd and data circuits
are reset after a tuning timeout.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
In the busy response case (i.e. !host->data), an unexpected data interrupt
would result in clearing the data command as though it had completed but
without informing the upper layers and thus resulting in a hang. Fix by
only clearing the data command for data interrupts that are expected.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org # v4.8+
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
CMD line reset during an ongoing data transfer can cause the data transfer
to hang. Fix by delaying the reset until the data transfer is finished.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org # v4.8+
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Add the "reset" as name of reset controller.
This is for preventing the wrong operation. Even if some SoC has reset
controller, doesn't define "resets" in device-tree.
Then it might be waiting for reset controller and it should be stuck.
Fixes: d6786fefe8 ("mmc: dw_mmc: add reset support to dwmmc host controller")
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Acked-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Fix to return a negative error code from the platform_get_irq_byname()
error handling case instead of 0, as done elsewhere in this function.
Fixes: ad81d38710 ("mmc: sdhci-msm: Add support for UHS cards")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Georgi Djakov <georgi.djakov@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
platform_get_resource can be returned the NULL pointer.
Then regs->start should be referred to NULL Pointer.
devm_ioremap_resource() checks whether res is NULL or not.
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Accesses of the rtsx sdmmc's parent device, which is the rtsx usb device,
must be done when it's runtime resumed. Currently this isn't case when
changing the led, so let's fix this by adding a pm_runtime_get_sync() and
a pm_runtime_put() around those operations.
Reported-by: Ritesh Raj Sarraf <rrs@researchut.com>
Tested-by: Ritesh Raj Sarraf <rrs@researchut.com>
Cc: <stable@vger.kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
The rtsx_usb_sdmmc driver may bail out in its ->set_ios() callback when no
SD card is inserted. This is wrong, as it could cause the device to remain
runtime resumed when it's unused. Fix this behaviour.
Tested-by: Ritesh Raj Sarraf <rrs@researchut.com>
Cc: <stable@vger.kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Potentially overflowing expression 1000000 * data->timeout_clks with
type unsigned int is evaluated using 32-bit arithmetic, and then used
in a context that expects an expression of type unsigned long long.
To avoid overflow, cast 1000000U to type unsigned long long.
Special thanks to Coverity.
Fixes: 7f05538af7 ("mmc: sdhci: fix data timeout (part 2)")
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Cc: stable@vger.kernel.org # v3.15+
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
- The DMA error interrupt bit is in a different position as
compared to the sdhci standard. This is accounted for in
many cases, but not handled in the case of clearing the
INT_STATUS register by writing a 1 to that location.
- The HOST_CONTROL register is very different as compared to
the sdhci standard. This is accounted for in the write
case, but not when read back out (which it is in the sdhci
code).
Signed-off-by: Dave Russell <david.russell@datasoft.com>
Signed-off-by: Aaron Brice <aaron.brice@datasoft.com>
Acked-by: Dong Aisheng <aisheng.dong@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Some Intel controllers (e.g. BXT) might fail to set bus power after a
D3 -> D0 transition due to the present state not yet having propagated.
Retry for up to 2 milliseconds.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Let devices define their own sdhci_ops so that device-specific variations
can be implemented without adding quirks.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Unlike other cases, sdhci_set_power() does not reflect the default
implementation of the ->set_power() callback. Rename it and create
sdhci_set_power() that is the default implementation.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Multi-block data transfers can specify the number of blocks either using a
Set Block Count command (CMD23) or by sending a STOP command (CMD12) after
the required number of blocks has transferred. CMD23 is preferred, but some
cards don't support it. CMD12 with R1b response is used for writes, and
R1 response for reads.
Some SDHCI host controllers give a Transfer Complete (TC) interrupt for the
STOP command (CMD12) whether or not a R1b response has been specified. The
quirk SDHCI_QUIRK2_STOP_WITH_TC identifies those host controllers, but the
implementation only considers the case where the TC interrupt arrives at
the same time as the Command Complete (CC) interrupt. However,
occasionally TC arrives before CC. That is harmless, but does generate an
error message "Got data interrupt 0x00000002 even though no data operation
was in progress".
A simpler approach is to force R1b response onto all STOP commands, because
SDHCI will handle TC before CC in the general case, so do that.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Per the vendor's requirement, we shouldn't do any setting for
1.8V Signaling Enable, otherwise the interaction/behaviour between
phy and controller will be undefined. Mostly it works fine if we do
that, but we still see failures. Anyway, let's fix it to meet the
vendor's requirement. The error log looks like:
[ 93.405085] mmc1: unexpected status 0x800900 after switch
[ 93.408474] mmc1: switch to bus width 1 failed
[ 93.408482] mmc1: mmc_select_hs200 failed, error -110
[ 93.408492] mmc1: error -110 during resume (card was removed?)
[ 93.408705] PM: resume of devices complete after 213.453 msecs
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Per JESD84-B51 P49, Host need to change frequency to <=52MHz
after setting HS_TIMING to 0x1, and host may changes frequency
to <= 200MHz after setting HS_TIMING to 0x3. That means the card
expects the clock rate to increase from the current used f_init
(which is less than 400KHz, but still being less than 52MHz) to
52MHz, otherwise we find some eMMC devices significantly report
failure when sending status.
Reported-by: Xiao Yao <xiaoyao@rock-chips.com>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
When introducing hs400es, I didn't notice that we haven't
switched voltage to 1V2 or 1V8 for it. That happens to work
as the first controller claiming to support hs400es, arasan(5.1),
which is designed to only support 1V8. So the voltage is fixed to 1V8.
But it actually is wrong, and will not fit for other host controllers.
Let's fix it.
Fixes: commit 81ac2af657 ("mmc: core: implement enhanced strobe support")
Cc: <stable@vger.kernel.org>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
We get 1 warning when building kernel with W=1:
drivers/mmc/card/block.c:2147:5: warning: no previous prototype for
'mmc_blk_issue_rq' [-Wmissing-prototypes]
In fact, this function is declared in drivers/mmc/card/block.h, so this
patch adds missing header dependencies.
Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Fixes the following sparse warning:
drivers/mmc/host/sdhci-of-arasan.c:253:6: warning:
symbol 'sdhci_arasan_reset' was not declared. Should it be static?
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Remvoe the deprecated "supports-highspeed" property.
DWMMC controller will not use this property anymore.
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
msize and rx_wmark are properly initialized, we dont't
need to assign them again.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
It's very prone to make mistake as we might forget
to replace all PAGE_SIZEs with new values if we try
to modify the ring buffer size for whatever reasons.
Let's use a macro to define it.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
The original log didn't figure out that we could still
finish this transfer by PIO mode even if failing to use
DMA. And it should be kept for debug level instead of
error one.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
We could see an obvious race condition by test that
the former write operation by IDMAC aiming to clear
OWN bit reach right after the later configuration of
the same desc, which makes the IDMAC be in SUSPEND
state as the OWN bit was cleared by the asynchronous
write operation of IDMAC. The bug can be very easy
reproduced on RK3288 or similar when we reduce the
running rate of system buses and keep the CPU running
faster. So as two separate masters, IDMAC and cpu
write the same descriptor stored on the same address,
and this should be protected by adding check of OWN
bit before preparing new descriptors.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
We intend to add more check for descriptors when
preparing desc. Let's spilt out the separate body
to make the dw_mci_translate_sglist not so lengthy.
After spliting out these two functions, we could
remove dw_mci_translate_sglist and call both of them
when staring idmac.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Per spec, block size should always be 512 bytes for dual rate mode,
so any attempts to switch the block size under dual rate mode should
be neglected.
Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
The sdhci controller on xilinx zynq devices will not function unless
the CD bit is provided. http://www.xilinx.com/support/answers/61064.html
In cases where it is impossible to provide the CD bit in hardware,
setting the controller to test mode and then setting inserted to true
will get the controller to function without the CD bit.
When the device has the property xlnx,fails-without-test-cd the driver
changes the controller to test mode and sets test inserted to true to
make the controller function.
Signed-off-by: Zach Brown <zach.brown@ni.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
We need to add R1 without CRC support, refactor the bus width routine a
little and extend a quirk check. To support "non-removable;" we need a
workaround which will be hopefully removed when reworking PM soon.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
We have enough vtables in the kernel as it is, we don't need
this one to create even more artificial separation of concerns.
As is proved by the Makefile:
obj-$(CONFIG_MMC_BLOCK) += mmc_block.o
mmc_block-objs := block.o queue.o
block.c and queue.c are baked into the same mmc_block.o object.
So why would one of these objects access a function in the
other object by dereferencing a pointer?
Create a new block.h header file for the single shared function
from block to queue and remove the function pointer and just
call the queue request function.
Apart from making the code more readable, this also makes link
optimizations possible and probably speeds up the call as well.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Set MMC_CAP_CMD_DURING_TFR for Intel BYT and related eMMC host controllers.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Set MMC_CAP_CMD_DURING_TFR for Intel BYT and related eMMC host controllers.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Now SDHCI supports commands during transfer, enable support for the core
API.
There are 3 small changes needed:
First, auto-CMD12 cannot be used with a cap_cmd_during_tfr request because
the host controller cannot expect the command line to be available.
Secondly, a cap_cmd_during_tfr request must not send a stop command, again
because the host controller cannot expect the command line to be available.
Thirdly, when a cap_cmd_during_tfr command completes, use
mmc_command_complete() to notify the upper layers that the command line is
now available for further commands.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Add 6 tests for sending commands during transfer. The tests are:
* Commands during read - no Set Block Count (CMD23).
* Commands during write - no Set Block Count (CMD23).
* Commands during read - use Set Block Count (CMD23).
* Commands during write - use Set Block Count (CMD23).
* Commands during non-blocking read - use Set Block Count (CMD23).
* Commands during non-blocking write - use Set Block Count (CMD23).
For a range of transfer sizes, the tests start an ongoing data transfer and
then repeatedly send the status command (CMD13) while the transfer
continues. The tests pass if all requests complete with no errors. The host
controller driver must support MMC_CAP_CMD_DURING_TFR.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
A host controller driver exposes its capability using caps flag
MMC_CAP_CMD_DURING_TFR. A driver with that capability can accept requests
that are marked mrq->cap_cmd_during_tfr = true. Then the driver informs the
upper layers when the command line is available for further commands by
calling mmc_command_done(). Because of that, the driver will not then
automatically send STOP commands, and it is the responsibility of the upper
layer to send a STOP command if it is required.
For requests submitted through the mmc_wait_for_req() interface, the caller
sets mrq->cap_cmd_during_tfr = true which causes mmc_wait_for_req() in fact
not to wait. The caller can then send commands that do not use the data
lines. Finally the caller can wait for the transfer to complete by calling
mmc_wait_for_req_done() which is now exported.
For requests submitted through the mmc_start_req() interface, the caller
again sets mrq->cap_cmd_during_tfr = true, but mmc_start_req() anyway does
not wait. The caller can then send commands that do not use the data
lines. Finally the caller can wait for the transfer to complete in the
normal way i.e. calling mmc_start_req() again.
Irrespective of how a cap_cmd_during_tfr request is started,
mmc_is_req_done() can be called if the upper layer needs to determine if
the request is done. However the appropriate waiting function (either
mmc_wait_for_req_done() or mmc_start_req()) must still be called.
The implementation consists primarily of a new completion
mrq->cmd_completion which notifies when the command line is available for
further commands. That completion is completed by mmc_command_done().
When there is an ongoing data transfer, calls to mmc_wait_for_req() will
automatically wait on that completion, so the caller does not have to do
anything special.
Note, in the case of errors, the driver may call mmc_request_done() without
calling mmc_command_done() because mmc_request_done() always calls
mmc_command_done().
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Clear incorrect SDHCI_CAN_64BIT capability on Broadcom MIPS based SoCs.
The MIPS based SoCs are using ADMA only, but the several SoCs have the
incorrect capability bit about ADMA 64-bit. The "brcm,bcm7425-sdhci" is
compatible string for MIPS based SoC.
Signed-off-by: Jaedon Shin <jaedon.shin@gmail.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
A64 SoC features a MMC controller which need only the mod clock, and can
calibrate delay by itself. This patch adds support for the new MMC
controller IP core.
Signed-off-by: Icenowy Zheng <icenowy@aosc.xyz>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
In most cases the 'card->erase_size' is power of 2, then the round_up/down()
function is more efficient than '%' operation when the 'card->erase_size' is
power of 2.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Tested-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
In order to clean up the mmc_erase() function and do some optimization
for erase size alignment, factor out the guts of erase size alignment
into mmc_align_erase_size() function.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Tested-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
platform_get_irq() returns an error value on failure, not NO_IRQ,
so the error handling here could never work.
This changes the code to propagate the error value instead.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
In cases when the host->max_busy_timeout isn't specified, the calculated
number of maximum discard sectors defaults to UINT_MAX. This may cause a
too long timeout for a discard request.
Avoid this by using a default maximum erase timeout of 60s, used when we
calculate the maximum number of sectors that are allowed to be discarded
per request.
Do note that the minimum number of sectors to be discarded is still at
least one "preferred erase size".
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Jaehoon Chung