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From: Peter Maydell <peter.maydell@linaro.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: QEMU Developers <qemu-devel@nongnu.org>
Subject: Re: How to tell DMA controller in qemu to terminate transfer ?
Date: Fri, 10 Jan 2020 10:36:20 +0000	[thread overview]
Message-ID: <CAFEAcA9t4X5Xnk0aS4C-vhKX2c3GA9XQ3zZRGYVGLEQsG=EgeQ@mail.gmail.com> (raw)
In-Reply-To: <20200108183553.GA5608@roeck-us.net>

On Wed, 8 Jan 2020 at 18:36, Guenter Roeck <linux@roeck-us.net> wrote:
>
> Hi,
>
> I am trying to fix DMA support with Exynos4210. The original commit
> 59520dc65e ("hw/arm/exynos4210: Add DMA support for the Exynos4210") doesn't
> really work, primarily because it assigns wrong interrupt lines (no idea
> how I thought I tested that).
>
> Problem I have right now is that the pl330 peripheral DMA in Exynos4210
> depends on a signal from the peripheral device (here: serial ports)
> to end a DMA transfer. To make this work, I need a signal from
> exynos4210_uart.c to pl330.c to terminate the DMA after the receive
> buffer is empty.
>
> How can I implement this in qemu ?

That depends. How does the UART signal the DMA controller
in real hardware? If there's a signal line of some kind,
then you can model that with a qemu_irq line which the UART
exposes and raises/lowers at the right time, that's then
plumbed through by the SoC to the DMA controller.

thanks
-- PMM


  reply	other threads:[~2020-01-10 10:37 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-08 18:35 How to tell DMA controller in qemu to terminate transfer ? Guenter Roeck
2020-01-10 10:36 ` Peter Maydell [this message]
2020-01-10 12:46   ` Guenter Roeck
2020-01-10 18:02   ` Guenter Roeck

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