From: sashiko-bot@kernel.org
To: "James Hilliard" <james.hilliard1@gmail.com>
Cc: linux-serial@vger.kernel.org, imx@lists.linux.dev, Frank.Li@kernel.org
Subject: Re: [PATCH v11 4/8] serial: 8250_omap: quiesce DMA IRQ handling before shutdown
Date: Tue, 10 Nov 2026 04:29:28 +0000 [thread overview]
Message-ID: <sashiko-outbox-206203@kernel.org> (raw)
In-Reply-To: <20261109-submit-serial-8250-dma-cancel-v1-v11-4-6364edca63d6@gmail.com>
Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] serial: 8250_omap: UART_OMAP_EFR2 cleared before locked RX
DMA flush
--
commit 4f01158f98251ff9fc53053baff46ab365f1866d
Author: James Hilliard <james.hilliard1@gmail.com>
serial: 8250_omap: quiesce DMA IRQ handling before shutdown
This commit gates DMA IRQ handling on up->dma->shutting_down under the
port lock, moves the final RX DMA flush into that locked section, and
switches omap_8250_shutdown() from disable_irq_nosync() to disable_irq()
before releasing DMA resources.
> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
> index 5e114dd8f9bfb..51013dd2d8510 100644
> --- a/drivers/tty/serial/8250/8250_omap.c
> +++ b/drivers/tty/serial/8250/8250_omap.c
> @@ -771,10 +771,6 @@ static void omap_8250_shutdown(struct uart_port *port)
> guard(serial8250_rpm)(up);
>
> flush_work(&priv->qos_work);
> - if (up->dma) {
> - guard(uart_port_lock_irq)(port);
> - omap_8250_rx_dma_flush(up);
> - }
>
> serial_out(up, UART_OMAP_WER, 0);
> if (priv->habit & UART_HAS_EFR2)
> @@ -782,13 +778,16 @@ static void omap_8250_shutdown(struct uart_port *port)
>
> /* Synchronize UART_IER access against the console. */
> scoped_guard(uart_port_lock_irq, port) {
> - if (up->dma)
> + if (up->dma) {
> up->dma->shutting_down = true;
> + omap_8250_rx_dma_flush(up);
> + }
> up->ier = 0;
> serial_out(up, UART_IER, 0);
> }
[Severity: Medium]
Can clearing UART_OMAP_EFR2 before acquiring port->lock leave
UART_OMAP_EFR2_TIMEOUT_BEHAVE set after shutdown?
Moving omap_8250_rx_dma_flush() into the locked block places it after
serial_out(up, UART_OMAP_EFR2, 0x0):
CPU0 CPU1
omap_8250_shutdown() omap_8250_dma_handle_irq()
serial_out(up, UART_OMAP_EFR2, 0x0)
uart_port_lock(port)
/* shutting_down is still false */
am654_8250_handle_rx_dma()
omap_8250_rx_dma(up)
serial_out(up, UART_OMAP_EFR2,
UART_OMAP_EFR2_TIMEOUT_BEHAVE)
uart_port_unlock(port)
uart_port_lock_irq(port)
up->dma->shutting_down = true
omap_8250_rx_dma_flush(up) <-- EFR2 is not cleared again
Neither omap_8250_startup() nor omap8250_restore_regs() resets
UART_OMAP_EFR2, so UART_OMAP_EFR2_TIMEOUT_BEHAVE stays set across
shutdown. Clearing UART_OMAP_EFR2 inside the port->lock block after
omap_8250_rx_dma_flush() would also match the flush-then-clear order in
am654_8250_handle_rx_dma().
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261109-submit-serial-8250-dma-cancel-v1-v11-0-6364edca63d6@gmail.com?part=4
next prev parent reply other threads:[~2026-11-10 4:29 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-10 4:00 [PATCH v11 0/8] serial: 8250: serialize DMA cancellation with buffer reuse James Hilliard
2026-11-10 4:00 ` [PATCH v11 1/8] serial: 8250_omap: separate locked TX DMA completion processing James Hilliard
2026-11-10 4:00 ` [PATCH v11 2/8] serial: serialize asynchronous write wakeups with the port lock James Hilliard
2026-11-10 4:00 ` [PATCH v11 3/8] serial: 8250_omap: serialize RX DMA completion and flushing James Hilliard
2026-11-10 4:00 ` [PATCH v11 4/8] serial: 8250_omap: quiesce DMA IRQ handling before shutdown James Hilliard
2026-11-10 4:29 ` sashiko-bot [this message]
2026-11-10 4:00 ` [PATCH v11 5/8] serial: core: allow drivers to reserve flushed transmit storage James Hilliard
2026-11-10 4:00 ` [PATCH v11 6/8] serial: 8250: drain canceled TX DMA before reusing its buffer James Hilliard
2026-11-10 4:00 ` [PATCH v11 7/8] serial: 8250: retire canceled RX DMA before reusing the receive buffer James Hilliard
2026-11-10 21:05 ` Raul E Rangel
2026-11-10 4:00 ` [PATCH v11 8/8] serial: 8250: retain DMA resources when termination fails James Hilliard
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