In some circumstances the current implementation of the SPI memory
operations may occasionally fail even though they are executed in the
atomic context. This may happen if the system bus is relatively slow in
comparison to the SPI bus frequency, or there is a concurrent access to
it, which makes the MMIO-operations occasionally stalling before
push-pulling data from the DW APB SPI FIFOs. These two problems we've
discovered on the Baikal-T1 SoC. In order to fix them we have no choice
but to set an artificial limitation on the SPI bus speed.
Note currently this limitation will be only applicable for the memory
operations, since the standard SPI core interface is implemented with an
assumption that there is no problem with the automatic CS toggling.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-19-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Aside from the synchronous Tx-Rx mode, which has been utilized to create
the normal SPI transfers in the framework of the DW SSI driver, DW SPI
controller supports Tx-only and EEPROM-read modes. The former one just
enables the controller to transmit all the data from the Tx FIFO ignoring
anything retrieved from the MISO lane. The later mode is so called
write-then-read operation: DW SPI controller first pushes out all the data
from the Tx FIFO, after that it'll automatically receive as much data as
has been specified by means of the CTRLR1 register. Both of those modes
can be used to implement the memory operations supported by the SPI-memory
subsystem.
The memory operation implementation is pretty much straightforward, except
a few peculiarities we have had to take into account to make things
working. Since DW SPI controller doesn't provide a way to directly set and
clear the native CS lane level, but instead automatically de-asserts it
when a transfer going on, we have to make sure the Tx FIFO isn't empty
during entire Tx procedure. In addition we also need to read data from the
Rx FIFO as fast as possible to prevent it' overflow with automatically
fetched incoming traffic. The denoted peculiarities get to cause even more
problems if DW SSI controller is equipped with relatively small FIFO and
is connected to a relatively slow system bus (APB) (with respect to the
SPI bus speed). In order to workaround the problems for as much as it's
possible, the memory operation execution procedure collects all the Tx
data into a single buffer and disables the local IRQs to speed the
write-then-optionally-read method up.
Note the provided memory operations are utilized by default only if
a glue driver hasn't provided a custom version of ones and this is not
a DW APB SSI controller with fixed automatic CS toggle functionality.
Co-developed-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-18-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
The DW SSI errors handling method can be generically implemented for all
types of the transfers: IRQ, DMA and poll-based ones. It will be a
function which checks the overflow/underflow error flags and resets the
controller if any of them is set. In the framework of this commit we make
use of the new method to detect the errors in the IRQ- and DMA-based SPI
transfer execution procedures.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-17-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
By design of the currently available native set_cs callback, the CS
de-assertion will be done only if it's required by the corresponding
controller capability. But in order to pre-fill the Tx FIFO buffer with
data during the SPI memory ops execution the SER register needs to be left
cleared before that. We'll also need a way to explicitly set and clear the
corresponding CS bit at a certain moment of the operation. Let's alter
the set_cs function then to also de-activate the CS, when it's required.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-15-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
It's pointless to enable the chip back if the DMA setup procedure fails,
since we'll disable it on the next transfer anyway. For the same reason We
don't do that in case of a failure detected in any other methods called
from the transfer_one() method.
While at it consider any non-zero value returned from the dma_setup
callback to be erroneous as it's supposed to be in the kernel.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-13-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
It's theoretically erroneous to enable IRQ before the chip is turned on.
If IRQ handler gets executed before the chip is enabled, then any data
written to the Tx FIFO will be just ignored.
I say "theoretically" because we haven't noticed any problem with that,
but let's fix it anyway just in case...
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-12-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
In order to make the transfer_one() callback method more readable and
for unification with the DMA-based transfer, let's detach the IRQ setup
procedure into a dedicated function. While at it rename the IRQ-based
transfer handler function to be dw_spi-prefixe and looking more like the
DMA-related one.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-11-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Current IRQ-based SPI transfer execution procedure doesn't work well at
the final stage of the execution. If all the Tx data is sent out (written
to the Tx FIFO) but there is some data left to receive, the Tx FIFO Empty
IRQ will constantly happen until all of the requested inbound data is
received. Though for a short period of time, but it will make the system
less responsive. In order to fix that let's refactor the SPI transfer
execution procedure by taking the Rx FIFO Full IRQ into account. We'll read
and write SPI transfer data each time the IRQ happens as before. If all
the outbound data is sent out, we'll disable the Tx FIFO Empty IRQ. If
there is still some data to receive, we'll adjust the Rx FIFO Threshold
level, so the next IRQ would be raised at the moment of all incoming data
being available in the Rx FIFO.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-10-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
The Tx and Rx data write/read procedure can be significantly simplified by
using Tx/Rx transfer lengths instead of the end pointers. By having the
Tx/Rx data leftover lengths (in the number of transfer words) we can get
rid of all subtraction and division operations utilized here and there in
the tx_max(), rx_max(), dw_writer() and dw_reader() methods. Such
modification will not only give us the more optimized IO procedures, but
will make the data IO methods much more readable than before.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-9-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
DW APB SSI controller can be used by the two SPI core interfaces:
traditional SPI transfers and SPI memory operations. The controller needs
to be accordingly configured at runtime when the corresponding operations
are executed. In order to do that for the both interfaces from a single
function we introduce a new data wrapper for the transfer mode, data
width, number of data frames (for the automatic data transfer) and the bus
frequency. It will be used by the update_config() method to tune the DW
APB SSI up.
The update_config() method is made exported to be used not only by the DW
SPI core driver, but by the glue layer drivers too. This will be required
in a coming further commit.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-8-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Rx sample delay can be SPI device specific, and should be synchronously
initialized with the rest of the communication and peripheral device
related controller setups. So let's move the Rx-sample delay setup into
the DW APB SSI configuration update method.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-7-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
The code currently responsible for the SPI communication speed setting up
is a bit messy. Most likely for some historical reason the bus frequency
is saved in the peripheral chip private data. It's pointless now since the
custom communication speed is a SPI-transfer-specific thing and only if
there is no SPI transfer data specified (like during the SPI memory
operations) it can be taken from the SPI device structure. But even in the
later case there is no point in having the clock divider and the SPI bus
frequency saved in the chip data, because the controller can be used for
both SPI-transfer-based and SPI-transfer-less communications. From
software point of view keeping the current clock divider in an SPI-device
specific storage may give a small performance gain (to avoid sometimes a
round-up division), but in comparison to the total SPI transfer time it
just doesn't worth saving a few CPU cycles in comparison to the total SPI
transfer time while having the harder to read code. The only optimization,
which could worth preserving in the code is to avoid unnecessary DW SPI
controller registers update if it's possible. So to speak let's simplify
the SPI communication speed update procedure by removing the clock-related
fields from the peripheral chip data and update the DW SPI clock divider
only if it's really changed. The later change is reached by keeping the
effective SPI bus speed in the internal DW SPI private data.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-6-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
The SPI bus speed update functionality will be useful in another parts of
the driver too (like to implement the SPI memory operations and from the
DW SPI glue layers). Let's move it to the update_cr0() method then and
since the later is now updating not only the CTRLR0 register alter its
prototype to have a generic function name not related to CR0.
Leave the too long line with the chip->clk_div setting as is for now,
since it's going to be changed later anyway.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-5-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Indeed there is no point in detecting the SPI peripheral device parameters
and initializing the CR0 register fields each time an SPI transfer is
executed. Instead let's define a dedicated CR0 chip-data member, which
will be initialized in accordance with the SPI device settings at the
moment of setting it up.
By doing so we'll finally make the SPI device chip_data serving as it's
supposed to - to preserve the SPI device specific DW SPI configuration.
See spi-fsl-dspi.c, spi-pl022.c, spi-pxa2xx.c drivers for example of the
way the chip data is utilized.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-4-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Currently DWC SSI core is supported by means of setting up the
core-specific update_cr0() callback. It isn't suitable for multiple
reasons. First of all having exported several methods doing the same thing
but for different chips makes the code harder to maintain. Secondly the
spi-dw-core driver exports the methods, then the spi-dw-mmio driver sets
the private data callback with one of them so to be called by the core
driver again. That makes the code logic too complicated. Thirdly using
callbacks for just updating the CR0 register is problematic, since in case
if the register needed to be updated from different parts of the code,
we'd have to create another callback (for instance the SPI device-specific
parameters don't need to be calculated each time the SPI transfer is
submitted, so it's better to pre-calculate the CR0 data at the SPI-device
setup stage).
So keeping all the above in mind let's discard the update_cr0() callbacks,
define a generic and static dw_spi_update_cr0() method and create the
DW_SPI_CAP_DWC_SSI capability, which when enabled would activate the
alternative CR0 register layout.
While at it add the comments to the code path of the normal DW APB SSI
controller setup to make the dw_spi_update_cr0() method looking coherent.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-3-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Simplify the dw_spi_add_host() method a bit by replacing the currently
implemented default set_cs callback setting up and later having it
overwritten by a custom function with direct if-else-based callback
assignment.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20201007235511.4935-2-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
There is no point in having the commit 19b61392c5 ("spi: spi-dw: Add
lock protect dw_spi rx/tx to prevent concurrent calls") applied. The
commit author made an assumption that the problem with the rx data
mismatch was due to the lack of the data protection. While most likely it
was caused by the lack of the memory barrier. So having the
commit bfda044533 ("spi: dw: use "smp_mb()" to avoid sending spi data
error") applied would be enough to fix the problem.
Indeed the spin unlock operation makes sure each memory operation issued
before the release will be completed before it's completed. In other words
it works as an implicit one way memory barrier. So having both smp_mb()
and the spin_unlock_irqrestore() here is just redundant. One of them would
be enough. It's better to leave the smp_mb() since the Tx/Rx buffers
consistency is provided by the data transfer algorithm implementation:
first we initialize the buffers pointers, then make sure the assignments
are visible by the other CPUs by calling the smp_mb(), only after that
enable the interrupt, which handler uses the buffers.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112914.26501-5-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
In a further commit we'll have to get rid of the update_cr0() callback and
define a DW SSI capability instead. Since Keem Bay master/slave
functionality is controller by the CTRL0 register bitfield, we need to
first move the master mode selection into the internal corresponding
update_cr0 method, which would be activated by means of the dedicated
DW_SPI_CAP_KEEMBAY_MST capability setup.
Note this will be also useful if the driver will be ever altered to
support the DW SPI slave interface.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112914.26501-11-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
There are several vendor-specific versions of the DW SPI controllers,
each of which may have some peculiarities with respect to the original
IP-core. Seeing it has already caused adding flags and a callback into the
DW SPI private data, let's introduce a generic capabilities interface to
tune the generic DW SPI controller driver up in accordance with the
particular controller specifics. It's done by converting a simple
Alpine-specific CS-override capability into the DW SPI controller
capability activated by setting the DW_SPI_CAP_CS_OVERRIDE flag.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112914.26501-10-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Keeping SPI peripheral devices type is pointless since first it hasn't
been functionally utilized by any of the client drivers/code and second it
won't work for Microwire type at the very least. Moreover there is no
point in setting up the type by means of the chip-data in the modern
kernel. The peripheral devices with specific interface type need to be
detected in order to activate the corresponding frame format. It most
likely will require some peripheral device specific DT property or
whatever to find out the interface protocol. So let's remove the serial
interface type fields from the DW APB SSI controller and the SPI
peripheral device private data.
Note we'll preserve the explicit SSI_MOTO_SPI interface type setting up to
signify the only currently supported interface protocol.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112914.26501-9-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
It's a good practice to disable all IRQs if a device is fully unused. In
our case it is supposed to be done before requesting the IRQ and after the
last byte of an SPI transfer is received. In the former case it's required
to prevent the IRQ handler invocation before the driver data is fully
initialized (which may happen if the IRQs status has been left uncleared
before the device is probed). So we just moved the spi_hw_init() method
invocation to the earlier stage before requesting the IRQ. In the later
case there is just no point in having any of the IRQs enabled between SPI
transfers and when there is no SPI message currently being processed.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112914.26501-7-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Since n_bytes field of the DW SPI private data is also utilized by the
IRQ handler, we need to make sure it' initialization is done before the
memory barrier.
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200920112914.26501-4-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
This add support for the RX_SAMPLE_DLY register. If enabled in the
Designware IP, it allows tuning of the rx data signal by means of an
internal rx sample fifo.
The register is controlled by the rx-sample-delay-ns DT property,
which is defined per SPI slave as well on controller level.
The controller level rx-sample-delay-ns will apply to all slaves
without the property explicitly defined.
The register is located at offset 0xf0, and if the option is not
enabled in the IP, changing the register will have no effect. The
register will only be written if any slave defines a nonzero value
(after scaling by the clock period).
Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Link: https://lore.kernel.org/r/20200824203010.2033-2-lars.povlsen@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Generic DMA support is going to be part of the DW APB SSI core object.
In order to preserve the kernel loadable module name as spi-dw.ko, let's
add the "-core" suffix to the object with generic DW APB SSI code and
build it into the target spi-dw.ko driver.
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Georgy Vlasov <Georgy.Vlasov@baikalelectronics.ru>
Cc: Ramil Zaripov <Ramil.Zaripov@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-mips@vger.kernel.org
Cc: devicetree@vger.kernel.org
Link: https://lore.kernel.org/r/20200529131205.31838-10-Sergey.Semin@baikalelectronics.ru
Signed-off-by: Mark Brown <broonie@kernel.org>
Serge Semin