linux-kernel - Re: [PATCH v2] serial: amba-pl011: Fix RX stall when DMA is used

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Message-ID: <CACRpkdbhy7onqWwW90qU3UE_+nMrqvmX_Kjvdw+jqn=TjX2FkA@mail.gmail.com>
Date: Wed, 13 Nov 2024 11:06:14 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Kartik Rajput <kkartik@...dia.com>
Cc: linux@...linux.org.uk, gregkh@...uxfoundation.org, jirislaby@...nel.org, 
	theo.lebrun@...tlin.com, ilpo.jarvinen@...ux.intel.com, 
	l.sanfilippo@...bus.com, konradybcio@...nel.org, 
	christophe.jaillet@...adoo.fr, bigeasy@...utronix.de, arnd@...db.de, 
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH v2] serial: amba-pl011: Fix RX stall when DMA is used

On Wed, Nov 13, 2024 at 10:26 AM Kartik Rajput <kkartik@...dia.com> wrote:

> Function pl011_throttle_rx() calls pl011_stop_rx() to disable RX, which
> also disables the RX DMA by clearing the RXDMAE bit of the DMACR
> register. However, to properly unthrottle RX when DMA is used, the
> function pl011_unthrottle_rx() is expected to set the RXDMAE bit of
> the DMACR register, which it currently lacks. This causes RX to stall
> after the throttle API is called.
>
> Set RXDMAE bit in the DMACR register while unthrottling RX if RX DMA is
> used.
>
> Fixes: 211565b10099 ("serial: pl011: UPSTAT_AUTORTS requires .throttle/unthrottle")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Kartik Rajput <kkartik@...dia.com>

Looks right to me, thanks Kartik!
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij