Re: [PATCH] drm/omap: dsi: Fix deferred probe warnings

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On 12/04/2023 11:50, Laurent Pinchart wrote:
Hi Tony,

Thank you for the patch.

On Wed, Apr 12, 2023 at 10:39:53AM +0300, Tony Lindgren wrote:
We may not have dsi->dsidev initialized during probe, and that can
lead into various dsi related warnings as omap_dsi_host_detach() gets
called with dsi->dsidev set to NULL.

The warnings can be "Fixed dependency cycle(s)" followed by a
WARNING: CPU: 0 PID: 787 at drivers/gpu/drm/omapdrm/dss/dsi.c:4414.

How can this happen ? I assume .detach() can't be called without a
priori successful call to .attach(), that that sets dsi->dsidev.

I had a quick look, and the driver calls mipi_dsi_host_register() in probe, and mipi_dsi_host_unregister() in remove.

mipi_dsi_host_unregister() always calls mipi_dsi_detach(), but I don't think mipi_dsi_host_register() always calls attach, which happens later when the peripheral probes.


Let's fix the warnings by checking for a valid dsi->dsidev.

Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
  drivers/gpu/drm/omapdrm/dss/dsi.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/omapdrm/dss/dsi.c b/drivers/gpu/drm/omapdrm/dss/dsi.c
--- a/drivers/gpu/drm/omapdrm/dss/dsi.c
+++ b/drivers/gpu/drm/omapdrm/dss/dsi.c
@@ -4411,7 +4411,7 @@ static int omap_dsi_host_detach(struct mipi_dsi_host *host,
  	struct dsi_data *dsi = host_to_omap(host);
- if (WARN_ON(dsi->dsidev != client))
+	if (dsi->dsidev && WARN_ON(dsi->dsidev != client))
  		return -EINVAL;

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