Hello Rohit,
Thank you for the patch.
On Fri, Feb 16, 2024 at 04:40:43AM -0800, Rohit Visavalia wrote:
> Assert DisplayPort reset signal before deasserting,
> it is to clear out any registers programmed before booting kernel.
>
> Signed-off-by: Rohit Visavalia <rohit.visavalia@xxxxxxx>
> ---
> drivers/gpu/drm/xlnx/zynqmp_dp.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> index 1846c4971fd8..5a40aa1d4283 100644
> --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> @@ -1714,6 +1714,10 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub)
> goto err_free;
> }
>
> + ret = zynqmp_dp_reset(dp, true);
> + if (ret < 0)
> + return ret;
> +
This looks fine to me, so
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
However, looking at zynqmp_dp_reset(), we have
static int zynqmp_dp_reset(struct zynqmp_dp *dp, bool assert)
{
unsigned long timeout;
if (assert)
reset_control_assert(dp->reset);
else
reset_control_deassert(dp->reset);
/* Wait for the (de)assert to complete. */
timeout = jiffies + msecs_to_jiffies(RST_TIMEOUT_MS);
while (!time_after_eq(jiffies, timeout)) {
bool status = !!reset_control_status(dp->reset);
if (assert == status)
return 0;
cpu_relax();
}
dev_err(dp->dev, "reset %s timeout\n", assert ? "assert" : "deassert");
return -ETIMEDOUT;
}
That doesn't seem quite right. Aren't reset_control_assert() and
reset_control_deassert() supposed to be synchronous ? If so there should
be no need to wait, and if there's a need to wait, it could be a bug in
the reset controller driver. This should be fixed, and then the code in
probe could be replaced with a call to reset_control_reset().
> ret = zynqmp_dp_reset(dp, false);
> if (ret < 0)
> goto err_free;
--
Regards,
Laurent Pinchart
