kernel/drivers/tty/serial/msm_serial.c, branch master

tty: remove redundant condition checks

2025-09-06T13:49:58Z

Remove redundant condition checks and replace else if with else. Signed-off-by: Xichao Zhao Reviewed-by: Christophe Leroy Link: https://lore.kernel.org/r/20250905091321.437476-1-zhao.xichao@vivo.com Signed-off-by: Greg Kroah-Hartman

serial: msm: Configure correct working mode before starting earlycon

2025-04-11T14:58:47Z

The MSM UART DM controller supports different working modes, e.g. DMA or the "single-character mode", where all reads/writes operate on a single character rather than 4 chars (32-bit) at once. When using earlycon, __msm_console_write() always writes 4 characters at a time, but we don't know which mode the bootloader was using and we don't set the mode either. This causes garbled output if the bootloader was using the single-character mode, because only every 4th character appears in the serial console, e.g. "[ 00oni pi 000xf0[ 00i s 5rm9(l)l s 1 1 SPMTA 7:C 5[ 00A ade k d[ 00ano:ameoi .Q1B[ 00ac _idaM00080oo'" If the bootloader was using the DMA ("DM") mode, output would likely fail entirely. Later, when the full serial driver probes, the port is re-initialized and output works as expected. Fix this also for earlycon by clearing the DMEN register and reset+re-enable the transmitter to apply the change. This ensures the transmitter is in the expected state before writing any output. Cc: stable Fixes: 0efe72963409 ("tty: serial: msm: Add earlycon support") Signed-off-by: Stephan Gerhold Reviewed-by: Neil Armstrong Link: https://lore.kernel.org/r/20250408-msm-serial-earlycon-v1-1-429080127530@linaro.org Signed-off-by: Greg Kroah-Hartman

serial: Switch back to struct platform_driver::remove()

2024-10-11T06:13:28Z

After commit 0edb555a65d1 ("platform: Make platform_driver::remove() return void") .remove() is (again) the right callback to implement for platform drivers. Convert all platform drivers below drivers/tty/serial to use .remove(), with the eventual goal to drop struct platform_driver::remove_new(). As .remove() and .remove_new() have the same prototypes, conversion is done by just changing the structure member name in the driver initializer. Signed-off-by: Uwe Kleine-König Link: https://lore.kernel.org/r/20241007205803.444994-7-u.kleine-koenig@baylibre.com Signed-off-by: Greg Kroah-Hartman

serial: msm: check dma_map_sg() return value properly

2024-04-20T05:58:42Z

The -next commit f8fef2fa419f (tty: msm_serial: use dmaengine_prep_slave_sg()), switched to using dma_map_sg(). But the return value of dma_map_sg() is special: it returns number of elements mapped. And not a standard error value. The commit also forgot to reset dma->tx_sg in case of this failure. Fix both these mistakes. Thanks to Marek who helped debugging this. Signed-off-by: Jiri Slaby (SUSE) Reported-by: Marek Szyprowski Tested-by: Marek Szyprowski Link: https://lore.kernel.org/r/20240419080931.30949-1-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: serial: switch from circ_buf to kfifo

2024-04-09T13:28:03Z

Switch from struct circ_buf to proper kfifo. kfifo provides much better API, esp. when wrap-around of the buffer needs to be taken into account. Look at pl011_dma_tx_refill() or cpm_uart_tx_pump() changes for example. Kfifo API can also fill in scatter-gather DMA structures, so it easier for that use case too. Look at lpuart_dma_tx() for example. Note that not all drivers can be converted to that (like atmel_serial), they handle DMA specially. Note that usb-serial uses kfifo for TX for ages. omap needed a bit more care as it needs to put a char into FIFO to start the DMA transfer when OMAP_DMA_TX_KICK is set. In that case, we have to do kfifo_dma_out_prepare twice: once to find out the tx_size (to find out if it is worths to do DMA at all -- size >= 4), the second time for the actual transfer. All traces of circ_buf are removed from serial_core.h (and its struct uart_state). Signed-off-by: Jiri Slaby (SUSE) Cc: Al Cooper Cc: Matthias Brugger Cc: AngeloGioacchino Del Regno Cc: Kumaravel Thiagarajan Cc: Tharun Kumar P Cc: Russell King Cc: Vineet Gupta Cc: Richard Genoud Cc: Nicolas Ferre Cc: Alexandre Belloni Cc: Claudiu Beznea Cc: Alexander Shiyan Cc: Baruch Siach Cc: Maciej W. Rozycki Cc: Shawn Guo Cc: Sascha Hauer Cc: Fabio Estevam Cc: Neil Armstrong Cc: Kevin Hilman Cc: Jerome Brunet Cc: Martin Blumenstingl Cc: Taichi Sugaya Cc: Takao Orito Cc: Bjorn Andersson Cc: Konrad Dybcio Cc: Pali Rohár Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Cc: Aneesh Kumar K.V Cc: Naveen N. Rao Cc: Manivannan Sadhasivam Cc: Krzysztof Kozlowski Cc: Alim Akhtar Cc: Laxman Dewangan Cc: Thierry Reding Cc: Jonathan Hunter Cc: Orson Zhai Cc: Baolin Wang Cc: Chunyan Zhang Cc: Patrice Chotard Cc: Maxime Coquelin Cc: Alexandre Torgue Cc: David S. Miller Cc: Hammer Hsieh Cc: Peter Korsgaard Cc: Timur Tabi Cc: Michal Simek Cc: Sumit Semwal Cc: Christian König Link: https://lore.kernel.org/r/20240405060826.2521-13-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: msm_serial: use dmaengine_prep_slave_sg()

2024-04-09T13:28:03Z

This is a preparatory for the serial-to-kfifo switch. kfifo understands only scatter-gatter approach, so switch to that. No functional change intended, it's just dmaengine_prep_slave_single() inline expanded. And in this case, switch from dma_map_single() to dma_map_sg() too. This needs struct msm_dma changes. I split the rx and tx parts into an union. TX is now struct scatterlist, RX remains the old good phys-virt-count triple. Signed-off-by: Jiri Slaby (SUSE) Cc: Bjorn Andersson Cc: Konrad Dybcio Cc: linux-arm-msm@vger.kernel.org Link: https://lore.kernel.org/r/20240405060826.2521-12-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

serial: msm: Use uart_prepare_sysrq_char().

2024-03-02T21:06:21Z

The port lock is a spinlock_t which is becomes a sleeping lock on PREEMPT_RT. The driver splits the locking function into two parts: local_irq_save() and uart_port_lock() and this breaks PREEMPT_RT. Delay handling sysrq until port lock is dropped. Remove the special case in the console write routine an always use the complete locking function. Cc: Bjorn Andersson Cc: Konrad Dybcio Cc: linux-arm-msm@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/r/20240301215246.891055-6-bigeasy@linutronix.de Signed-off-by: Greg Kroah-Hartman

serial: msm: Use OPP table for DVFS support

2023-12-08T11:02:37Z

Parse the OPP table from the device tree and use dev_pm_opp_set_rate() instead of clk_set_rate() to allow making performance state votes specified in the OPP table (e.g. for power domains and interconnects). Without an OPP table in the device tree this will behave just as before this patch. Signed-off-by: Stephan Gerhold Link: https://lore.kernel.org/r/20231128-serial-msm-dvfs-v1-2-4f290d20a4be@kernkonzept.com Signed-off-by: Greg Kroah-Hartman

serial: msm: Convert to platform remove callback returning void

2023-11-23T19:12:33Z

The .remove() callback for a platform driver returns an int which makes many driver authors wrongly assume it's possible to do error handling by returning an error code. However the value returned is ignored (apart from emitting a warning) and this typically results in resource leaks. To improve here there is a quest to make the remove callback return void. In the first step of this quest all drivers are converted to .remove_new(), which already returns void. Eventually after all drivers are converted, .remove_new() will be renamed to .remove(). Trivially convert this driver from always returning zero in the remove callback to the void returning variant. Signed-off-by: Uwe Kleine-König Link: https://lore.kernel.org/r/20231110152927.70601-27-u.kleine-koenig@pengutronix.de Signed-off-by: Greg Kroah-Hartman

serial: msm: Use port lock wrappers

2023-09-18T09:18:12Z

When a serial port is used for kernel console output, then all modifications to the UART registers which are done from other contexts, e.g. getty, termios, are interference points for the kernel console. So far this has been ignored and the printk output is based on the principle of hope. The rework of the console infrastructure which aims to support threaded and atomic consoles, requires to mark sections which modify the UART registers as unsafe. This allows the atomic write function to make informed decisions and eventually to restore operational state. It also allows to prevent the regular UART code from modifying UART registers while printk output is in progress. All modifications of UART registers are guarded by the UART port lock, which provides an obvious synchronization point with the console infrastructure. To avoid adding this functionality to all UART drivers, wrap the spin_[un]lock*() invocations for uart_port::lock into helper functions which just contain the spin_[un]lock*() invocations for now. In a subsequent step these helpers will gain the console synchronization mechanisms. Converted with coccinelle. No functional change. Signed-off-by: Thomas Gleixner Reviewed-by: Bjorn Andersson Signed-off-by: John Ogness Link: https://lore.kernel.org/r/20230914183831.587273-42-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman