diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.19/950-0608-tty-amba-pl011-Make-TX-optimisation-conditional.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.19/950-0608-tty-amba-pl011-Make-TX-optimisation-conditional.patch | 85 |
1 files changed, 0 insertions, 85 deletions
diff --git a/target/linux/brcm2708/patches-4.19/950-0608-tty-amba-pl011-Make-TX-optimisation-conditional.patch b/target/linux/brcm2708/patches-4.19/950-0608-tty-amba-pl011-Make-TX-optimisation-conditional.patch deleted file mode 100644 index 8d40afb444..0000000000 --- a/target/linux/brcm2708/patches-4.19/950-0608-tty-amba-pl011-Make-TX-optimisation-conditional.patch +++ /dev/null @@ -1,85 +0,0 @@ -From 3e3c13488e4efa0236c47a98ee5e759bf1f7c757 Mon Sep 17 00:00:00 2001 -From: Phil Elwell <phil@raspberrypi.org> -Date: Thu, 11 Jul 2019 13:13:39 +0100 -Subject: [PATCH] tty: amba-pl011: Make TX optimisation conditional - -pl011_tx_chars takes a "from_irq" parameter to reduce the number of -register accesses. When from_irq is true the function assumes that the -FIFO is half empty and writes up to half a FIFO's worth of bytes -without polling the FIFO status register, the reasoning being that -the function is being called as a result of the TX interrupt being -raised. This logic would work were it not for the fact that -pl011_rx_chars, called from pl011_int before pl011_tx_chars, releases -the spinlock before calling tty_flip_buffer_push. - -A user thread writing to the UART claims the spinlock and ultimately -calls pl011_tx_chars with from_irq set to false. This reverts to the -older logic that polls the FIFO status register before sending every -byte. If this happen on an SMP system during the section of the IRQ -handler where the spinlock has been released, then by the time the TX -interrupt handler is called, the FIFO may already be full, and any -further writes are likely to be lost. - -The fix involves adding a per-port flag that is true iff running from -within the interrupt handler and the spinlock has not yet been released. -This flag is then used as the value for the from_irq parameter of -pl011_tx_chars, causing polling to be used in the unsafe case. - -Fixes: 1e84d22322ce ("serial/amba-pl011: Refactor and simplify TX FIFO handling") - -Signed-off-by: Phil Elwell <phil@raspberrypi.org> ---- - drivers/tty/serial/amba-pl011.c | 7 ++++++- - 1 file changed, 6 insertions(+), 1 deletion(-) - ---- a/drivers/tty/serial/amba-pl011.c -+++ b/drivers/tty/serial/amba-pl011.c -@@ -270,6 +270,7 @@ struct uart_amba_port { - unsigned int old_cr; /* state during shutdown */ - unsigned int fixed_baud; /* vendor-set fixed baud rate */ - char type[12]; -+ bool irq_locked; /* in irq, unreleased lock */ - #ifdef CONFIG_DMA_ENGINE - /* DMA stuff */ - bool using_tx_dma; -@@ -813,6 +814,7 @@ __acquires(&uap->port.lock) - if (!uap->using_tx_dma) - return; - -+ uap->irq_locked = 0; - dmaengine_terminate_async(uap->dmatx.chan); - - if (uap->dmatx.queued) { -@@ -939,6 +941,7 @@ static void pl011_dma_rx_chars(struct ua - fifotaken = pl011_fifo_to_tty(uap); - } - -+ uap->irq_locked = 0; - spin_unlock(&uap->port.lock); - dev_vdbg(uap->port.dev, - "Took %d chars from DMA buffer and %d chars from the FIFO\n", -@@ -1347,6 +1350,7 @@ __acquires(&uap->port.lock) - { - pl011_fifo_to_tty(uap); - -+ uap->irq_locked = 0; - spin_unlock(&uap->port.lock); - tty_flip_buffer_push(&uap->port.state->port); - /* -@@ -1482,6 +1486,7 @@ static irqreturn_t pl011_int(int irq, vo - int handled = 0; - - spin_lock_irqsave(&uap->port.lock, flags); -+ uap->irq_locked = 1; - status = pl011_read(uap, REG_RIS) & uap->im; - if (status) { - do { -@@ -1501,7 +1506,7 @@ static irqreturn_t pl011_int(int irq, vo - UART011_CTSMIS|UART011_RIMIS)) - pl011_modem_status(uap); - if (status & UART011_TXIS) -- pl011_tx_chars(uap, true); -+ pl011_tx_chars(uap, uap->irq_locked); - - if (pass_counter-- == 0) - break; |