linux-kernel - Re: [PATCH 3/4] drm: xlnx: zynqmp_dpsub: Don't generate vblank in live mode

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Message-ID: <beb551c7-bb7e-4cd0-b166-e9aad90c4620@ideasonboard.com>
Date: Wed, 17 Jan 2024 16:20:10 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Anatoliy Klymenko <anatoliy.klymenko@....com>,
 laurent.pinchart@...asonboard.com, maarten.lankhorst@...ux.intel.com,
 mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
 michal.simek@....com, dri-devel@...ts.freedesktop.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] drm: xlnx: zynqmp_dpsub: Don't generate vblank in
 live mode

On 13/01/2024 01:42, Anatoliy Klymenko wrote:
> Filter out status register against interrupts' mask.
> Some events are being reported via DP status register, even if
> corresponding interrupts have been disabled. Avoid processing
> of such events in interrupt handler context.

The subject talks about vblank and live mode, the the description 
doesn't. Can you elaborate in the desc a bit about when this is an issue 
and why it wasn't before?

> Signed-off-by: Anatoliy Klymenko <anatoliy.klymenko@....com>
> ---
>   drivers/gpu/drm/xlnx/zynqmp_dp.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> index d60b7431603f..571c5dbc97e5 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> @@ -1624,8 +1624,16 @@ static irqreturn_t zynqmp_dp_irq_handler(int irq, void *data)
>   	u32 status, mask;
>   
>   	status = zynqmp_dp_read(dp, ZYNQMP_DP_INT_STATUS);
> +	zynqmp_dp_write(dp, ZYNQMP_DP_INT_STATUS, status);
>   	mask = zynqmp_dp_read(dp, ZYNQMP_DP_INT_MASK);
> -	if (!(status & ~mask))
> +
> +	/*
> +	 * Status register may report some events, which corresponding interrupts
> +	 * have been disabled. Filter out those events against interrupts' mask.
> +	 */
> +	status &= ~mask;
> +
> +	if (!status)
>   		return IRQ_NONE;
>   
>   	/* dbg for diagnostic, but not much that the driver can do */
> @@ -1634,7 +1642,6 @@ static irqreturn_t zynqmp_dp_irq_handler(int irq, void *data)
>   	if (status & ZYNQMP_DP_INT_CHBUF_OVERFLW_MASK)
>   		dev_dbg_ratelimited(dp->dev, "overflow interrupt\n");
>   
> -	zynqmp_dp_write(dp, ZYNQMP_DP_INT_STATUS, status);
>   
>   	if (status & ZYNQMP_DP_INT_VBLANK_START)
>   		zynqmp_dpsub_drm_handle_vblank(dp->dpsub);

Moving the zynqmp_dp_write() is not related to this fix, is it? I think 
it should be in a separate patch.

  Tomi