The DMA TRE(Transfer ring element) buffer contains the DMA
buffer address. Accessing data from this address can cause
significant delays in SPI transfers, which can be mitigated to
some extent by utilizing immediate DMA support.
QCOM GPI DMA hardware supports an immediate DMA feature for data
up to 8 bytes, storing the data directly in the DMA TRE buffer
instead of the DMA buffer address. This enhancement enables faster
SPI data transfers.
This optimization reduces the average transfer time from 25 us to
16 us for a single SPI transfer of 8 bytes length, with a clock
frequency of 50 MHz.
Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@quicinc.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-QRD
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20241209075033.16860-1-quic_jseerapu@quicinc.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Rx operation on SPI GSI DMA is currently not working.
As per GSI spec, link_rx bit is to be set on GO TRE on tx
channel whenever there is going to be a DMA TRE on rx
channel. This is currently set for duplex operation only.
Set the bit for rx operation as well.
This is part of changes required to bring up Rx.
Fixes: 94b8f0e58f ("dmaengine: qcom: gpi: set chain and link flag for duplex")
Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/1671212293-14767-1-git-send-email-quic_vnivarth@quicinc.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
When building with CONFIG_UBSAN_UNSIGNED_OVERFLOW, clang decides not to
inline gpi_update_reg, which causes a linkage failure around __bad_mask:
ld.lld: error: undefined symbol: __bad_mask
>>> referenced by bitfield.h:119 (include/linux/bitfield.h:119)
>>> dma/qcom/gpi.o:(gpi_update_reg) in archive drivers/built-in.a
>>> referenced by bitfield.h:119 (include/linux/bitfield.h:119)
>>> dma/qcom/gpi.o:(gpi_update_reg) in archive drivers/built-in.a
If gpi_update_reg is not inlined, the mask value will not be known at
compile time so the check in field_multiplier stays in the final
object file, causing the above linkage failure. Always inline
gpi_update_reg so that this check can never fail.
Fixes: 5d0c3533a1 ("dmaengine: qcom: Add GPI dma driver")
Link: https://github.com/ClangBuiltLinux/linux/issues/1243
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Link: https://lore.kernel.org/r/20210112191214.1264793-1-natechancellor@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
gcc points out an incorrect error handling loop:
drivers/dma/qcom/gpi.c: In function 'gpi_ch_init':
drivers/dma/qcom/gpi.c:1254:15: error: iteration 2 invokes undefined behavior [-Werror=aggressive-loop-optimizations]
1254 | struct gpii *gpii = gchan->gpii;
| ^~~~
drivers/dma/qcom/gpi.c:1951:2: note: within this loop
1951 | for (i = i - 1; i >= 0; i++) {
| ^~~
Change the loop to correctly walk backwards through the
initialized fields rather than off into the woods.
Fixes: 5d0c3533a1 ("dmaengine: qcom: Add GPI dma driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20210103135738.3741123-1-arnd@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
drivers/dma/qcom/gpi.c:1419:3: warning: format '%lu' expects argument of
type 'long unsigned int', but argument 8 has type 'size_t {aka unsigned
int}' [-Wformat=]
drivers/dma/qcom/gpi.c:1427:31: warning: format '%lu' expects argument of
type 'long unsigned int', but argument 3 has type 'size_t {aka unsigned
int}' [-Wformat=]
drivers/dma/qcom/gpi.c:1447:3: warning: format '%llx' expects argument of
type 'long long unsigned int', but argument 4 has type 'dma_addr_t {aka
unsigned int}' [-Wformat=]
drivers/dma/qcom/gpi.c:1447:3: warning: format '%llx' expects argument of
type 'long long unsigned int', but argument 5 has type 'phys_addr_t {aka
unsigned int}' [-Wformat=]
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20201218104137.59200-1-nixiaoming@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This controller provides DMAengine capabilities for a variety of peripheral
buses such as I2C, UART, and SPI. By using GPI dmaengine driver, bus
drivers can use a standardize interface that is protocol independent to
transfer data between memory and peripheral.
Link: https://lore.kernel.org/r/20201109085450.24843-4-vkoul@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
