On 09/11/2020 19:06, Nikhil Devshatwar wrote:
> When removing the tidss driver, there is a warning reported by
> kernel about an unhandled interrupt for mhdp driver.
>
> [ 43.238895] irq 31: nobody cared (try booting with the "irqpoll" option)
> ... [snipped backtrace]
> [ 43.330735] handlers:
> [ 43.333020] [<000000005367c4f9>] irq_default_primary_handler threaded [<000000007e02b601>]
> cdns_mhdp_irq_handler [cdns_mhdp8546]
> [ 43.344607] Disabling IRQ #31
>
> This happens because as part of cdns_mhdp_bridge_hpd_disable, driver tries
> to disable the interrupts. While disabling the SW_EVENT interrupts,
> it accidentally enables the MBOX interrupts, which are not handled by
> the driver.
>
> Fix this with a read-modify-write to update only required bits.
> Do the same for enabling interrupts as well.
>
> Signed-off-by: Nikhil Devshatwar <nikhil.nd@xxxxxx>
> ---
> drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> index 2cd809eed827..6beccd2a408e 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> @@ -2146,7 +2146,8 @@ static void cdns_mhdp_bridge_hpd_enable(struct drm_bridge *bridge)
>
> /* Enable SW event interrupts */
> if (mhdp->bridge_attached)
> - writel(~(u32)CDNS_APB_INT_MASK_SW_EVENT_INT,
> + writel(readl(mhdp->regs + CDNS_APB_INT_MASK) &
> + ~CDNS_APB_INT_MASK_SW_EVENT_INT,
> mhdp->regs + CDNS_APB_INT_MASK);
> }
>
> @@ -2154,7 +2155,9 @@ static void cdns_mhdp_bridge_hpd_disable(struct drm_bridge *bridge)
> {
> struct cdns_mhdp_device *mhdp = bridge_to_mhdp(bridge);
>
> - writel(CDNS_APB_INT_MASK_SW_EVENT_INT, mhdp->regs + CDNS_APB_INT_MASK);
> + writel(readl(mhdp->regs + CDNS_APB_INT_MASK) |
> + CDNS_APB_INT_MASK_SW_EVENT_INT,
> + mhdp->regs + CDNS_APB_INT_MASK);
> }
>
> static const struct drm_bridge_funcs cdns_mhdp_bridge_funcs = {
Good catch. I wonder why we need the above functions... We already enable and disable the interrupts
when attaching/detaching the driver. And I think we want to get the interrupt even if we won't
report HPD (but I think we always do report it), as we need the interrupts to track the link status.
Tomi
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