kernel/linux.git/drivers/tty/serial/sh-sci.c, branch v4.19.77

serial: sh-sci: Fix TX DMA buffer flushing and workqueue races

2019-07-31T05:27:04+00:00

[ Upstream commit 8493eab02608b0e82f67b892aa72882e510c31d0 ] When uart_flush_buffer() is called, the .flush_buffer() callback zeroes the tx_dma_len field. This may race with the work queue function handling transmit DMA requests: 1. If the buffer is flushed before the first DMA API call, dmaengine_prep_slave_single() may be called with a zero length, causing the DMA request to never complete, leading to messages like: rcar-dmac e7300000.dma-controller: Channel Address Error happen and, with debug enabled: sh-sci e6e88000.serial: sci_dma_tx_work_fn: ffff800639b55000: 0...0, cookie 126 and DMA timeouts. 2. If the buffer is flushed after the first DMA API call, but before the second, dma_sync_single_for_device() may be called with a zero length, causing the transmit data not to be flushed to RAM, and leading to stale data being output. Fix this by: 1. Letting sci_dma_tx_work_fn() return immediately if the transmit buffer is empty, 2. Extending the critical section to cover all DMA preparational work, so tx_dma_len stays consistent for all of it, 3. Using local copies of circ_buf.head and circ_buf.tail, to make sure they match the actual operation above. Reported-by: Eugeniu Rosca Suggested-by: Yoshihiro Shimoda Signed-off-by: Geert Uytterhoeven Reviewed-by: Eugeniu Rosca Tested-by: Eugeniu Rosca Link: https://lore.kernel.org/r/20190624123540.20629-2-geert+renesas@glider.be Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

serial: sh-sci: Terminate TX DMA during buffer flushing

2019-07-31T05:27:04+00:00

[ Upstream commit 775b7ffd7d6d5db320d99b0a485c51e04dfcf9f1 ] While the .flush_buffer() callback clears sci_port.tx_dma_len since commit 1cf4a7efdc71cab8 ("serial: sh-sci: Fix race condition causing garbage during shutdown"), it does not terminate a transmit DMA operation that may be in progress. Fix this by terminating any pending DMA operations, and resetting the corresponding cookie. Signed-off-by: Geert Uytterhoeven Reviewed-by: Eugeniu Rosca Tested-by: Eugeniu Rosca Link: https://lore.kernel.org/r/20190624123540.20629-3-geert+renesas@glider.be Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

serial: sh-sci: disable DMA for uart_console

2019-06-09T07:17:21+00:00

commit 099506cbbc79c0bd52b19cb6b930f256dabc3950 upstream. As noted in commit 84b40e3b57ee ("serial: 8250: omap: Disable DMA for console UART"), UART console lines use low-level PIO only access functions which will conflict with use of the line when DMA is enabled, e.g. when the console line is also used for systemd messages. So disable DMA support for UART console lines. Reported-by: Michael Rodin Link: https://patchwork.kernel.org/patch/10929511/ Tested-by: Eugeniu Rosca Reviewed-by: Simon Horman Reviewed-by: Wolfram Sang Reviewed-by: Geert Uytterhoeven Cc: stable@vger.kernel.org Signed-off-by: George G. Davis Signed-off-by: Greg Kroah-Hartman Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Fix HSCIF RX sampling point calculation

2019-04-27T07:36:36+00:00

commit ace965696da2611af759f0284e26342b7b6cec89 upstream. There are several issues with the formula used for calculating the deviation from the intended rate: 1. While min_err and last_stop are signed, srr and baud are unsigned. Hence the signed values are promoted to unsigned, which will lead to a bogus value of deviation if min_err is negative, 2. Srr is the register field value, which is one less than the actual sampling rate factor, 3. The divisions do not use rounding. Fix this by casting unsigned variables to int, adding one to srr, and using a single DIV_ROUND_CLOSEST(). Fixes: 63ba1e00f178a448 ("serial: sh-sci: Support for HSCIF RX sampling point adjustment") Signed-off-by: Geert Uytterhoeven Reviewed-by: Mukesh Ojha Cc: stable Reviewed-by: Ulrich Hecht Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Fix HSCIF RX sampling point adjustment

2019-04-27T07:36:36+00:00

commit 6b87784b53592a90d21576be8eff688b56d93cce upstream. The calculation of the sampling point has min() and max() exchanged. Fix this by using the clamp() helper instead. Fixes: 63ba1e00f178a448 ("serial: sh-sci: Support for HSCIF RX sampling point adjustment") Signed-off-by: Geert Uytterhoeven Reviewed-by: Ulrich Hecht Reviewed-by: Wolfram Sang Acked-by: Dirk Behme Cc: stable Reviewed-by: Simon Horman Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Fix setting SCSCR_TIE while transferring data

2019-04-03T04:26:25+00:00

commit 93bcefd4c6bad4c69dbc4edcd3fbf774b24d930d upstream. We disable transmission interrupt (clear SCSCR_TIE) after all data has been transmitted (if uart_circ_empty(xmit)). While transmitting, if the data is still in the tty buffer, re-enable the SCSCR_TIE bit, which was done at sci_start_tx(). This is unnecessary processing, wasting CPU operation if the data transmission length is large. And further, transmit end, FIFO empty bits disabling have also been performed in the step above. Signed-off-by: Hoan Nguyen An Cc: stable Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Do not free irqs that have already been freed

2019-02-12T18:47:26+00:00

commit 4d95987a32db53f3beca76f8c4c8309ef6a5f192 upstream. Since IRQs might be muxed on some parts, we need to pay attention when we are freeing them. Otherwise we get the ugly WARNING "Trying to free already-free IRQ 20". Fixes: 628c534ae735 ("serial: sh-sci: Improve support for separate TEI and DRI interrupts") Cc: stable Signed-off-by: Chris Brandt Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Resume PIO in sci_rx_interrupt() on DMA failure

2019-02-12T18:47:11+00:00

[ Upstream commit 71ab1c0336c71ace5725740f200beca9667a339f ] On (H)SCIF, sci_submit_rx() is called in the receive interrupt handler. Hence if DMA submission fails, the interrupt handler should resume handling reception using PIO, else no more data is received. Make sci_submit_rx() return an error indicator, so the receive interrupt handler can act appropriately. Signed-off-by: Geert Uytterhoeven Reviewed-by: Simon Horman Acked-by: Wolfram Sang Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

serial: sh-sci: Fix locking in sci_submit_rx()

2019-02-12T18:47:11+00:00

[ Upstream commit dd1f2250da95e87cb3e612858f94b14f99445a7c ] Some callers of sci_submit_rx() hold the port spinlock, others don't. During fallback to PIO, the driver needs to obtain the port spinlock. If the lock was already held, spinlock recursion is detected, causing a deadlock: BUG: spinlock recursion on CPU#0. Fix this by adding a flag parameter to sci_submit_rx() for the caller to indicate the port spinlock is already held, so spinlock recursion can be avoided. Move the spin_lock_irqsave() up, so all DMA disable steps are protected, which is safe as the recently introduced dmaengine_terminate_async() can be called in atomic context. Signed-off-by: Geert Uytterhoeven Reviewed-by: Simon Horman Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin

serial: sh-sci: Fix receive on SCIFA/SCIFB variants with DMA

2018-11-27T15:13:01+00:00

[ Upstream commit 202dc3cc10b4d37e5251431acf8d5040a8876c7d ] On SCIFA and SCIFB serial ports with DMA support (i.e. some ports on R-Car Gen2 and RZ/G1 SoCs), receive DMA operations are submitted before the DMA channel pointer is initialized. Hence this fails, and the driver tries to fall back to PIO. However, at this early phase in the initialization sequence, fallback to PIO does not work, leading to a serial port that cannot receive any data. Fix this by calling sci_submit_rx() after initialization of the DMA channel pointer. Reported-by: Yoshihiro Shimoda Fixes: 2c4ee23530ffc022 ("serial: sh-sci: Postpone DMA release when falling back to PIO") Signed-off-by: Geert Uytterhoeven Reviewed-by: Wolfram Sang Tested-by: Wolfram Sang Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin