Re: [PATCH] drm/bridge/synopsys: dsi: Don't blindly call post_disable
On Thu, Apr 25, 2019 at 08:59:15PM +0300, Laurent Pinchart wrote:
> On Thu, Apr 25, 2019 at 12:39:27PM +, Matt Redfearn wrote:
> > On 25/04/2019 13:13, Andrzej Hajda wrote:
> >> On 24.04.2019 16:22, Matt Redfearn wrote:
> >>> The DRM documentation states that post_disable is an optional callback.
> >>> As such an implementing device may not populate it. To avoid panicing
> >>> the kernel by calling a NULL function pointer, we should NULL check it
> >>> before blindy calling it.
> >>>
> >>> Signed-off-by: Matt Redfearn
> >>
> >>> ---
> >>>
> >>> drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 3 ++-
> >>> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >>> b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >>> index 38e88071363..0ee440216b8 100644
> >>> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >>> @@ -805,7 +805,8 @@ static void dw_mipi_dsi_bridge_post_disable(struct
> >>> drm_bridge *bridge)
> >>>* This needs to be fixed in the drm_bridge framework and the
> >>> API
> >>>* needs to be updated to manage our own call chains...
> >>>*/
> >>> - dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
> >>> + if (dsi->panel_bridge->funcs->post_disable)
> >>> + dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
> >>>
> >>
> >> Why not drm_bridge_post_disable ?
> >
> > Ah - that seems like a nicer fix! Do you think the comment above
> > describing why this function pointer is called directly can be removed
> > as well if we go this route?
>
> It shouldn't be necessary to call ->post_disable manually here as the
> bridge core handles it internally. This is a hack to work around a
> problem, and should be fixed properly.
>
> > If someone calls drm_bridge_post_disable() on the Synposys DSI
> > drm_bridge it will go on to call post_disable on all other bridges in
> > the chain, in addition to us calling them here. Is it an issue to call
> > it multiple times?
>
> It depends on the panel implementation, but in general it's not a good
> idea. It may happen to work, but could break at any time in the future.
Double-checking the driver, the .attach() operation doesn't propagate to
the next bridge, so the bridge core will not know about it, and will not
propagate .post_disable() either. I think this should be fixed in a way
that uses the drm bridge core infrastructure.
> >>> if (dsi->slave) {
> >>> dw_mipi_dsi_disable(dsi->slave);
--
Regards,
Laurent Pinchart
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Re: [PATCH] drm/bridge/synopsys: dsi: Don't blindly call post_disable
Hi Matt,
On Thu, Apr 25, 2019 at 12:39:27PM +, Matt Redfearn wrote:
> On 25/04/2019 13:13, Andrzej Hajda wrote:
> > On 24.04.2019 16:22, Matt Redfearn wrote:
> >> The DRM documentation states that post_disable is an optional callback.
> >> As such an implementing device may not populate it. To avoid panicing
> >> the kernel by calling a NULL function pointer, we should NULL check it
> >> before blindy calling it.
> >>
> >> Signed-off-by: Matt Redfearn
> >
> >> ---
> >>
> >> drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 3 ++-
> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >> b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >> index 38e88071363..0ee440216b8 100644
> >> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> >> @@ -805,7 +805,8 @@ static void dw_mipi_dsi_bridge_post_disable(struct
> >> drm_bridge *bridge)
> >> * This needs to be fixed in the drm_bridge framework and the API
> >> * needs to be updated to manage our own call chains...
> >> */
> >> - dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
> >> + if (dsi->panel_bridge->funcs->post_disable)
> >> + dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
> >>
> >
> > Why not drm_bridge_post_disable ?
>
> Ah - that seems like a nicer fix! Do you think the comment above
> describing why this function pointer is called directly can be removed
> as well if we go this route?
It shouldn't be necessary to call ->post_disable manually here as the
bridge core handles it internally. This is a hack to work around a
problem, and should be fixed properly.
> If someone calls drm_bridge_post_disable() on the Synposys DSI
> drm_bridge it will go on to call post_disable on all other bridges in
> the chain, in addition to us calling them here. Is it an issue to call
> it multiple times?
It depends on the panel implementation, but in general it's not a good
idea. It may happen to work, but could break at any time in the future.
> >>if (dsi->slave) {
> >>dw_mipi_dsi_disable(dsi->slave);
--
Regards,
Laurent Pinchart
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Re: [PATCH] drm/bridge/synopsys: dsi: Don't blindly call post_disable
Hi Andrzej,
On 25/04/2019 13:13, Andrzej Hajda wrote:
> On 24.04.2019 16:22, Matt Redfearn wrote:
>> The DRM documentation states that post_disable is an optional callback.
>> As such an implementing device may not populate it. To avoid panicing
>> the kernel by calling a NULL function pointer, we should NULL check it
>> before blindy calling it.
>>
>> Signed-off-by: Matt Redfearn
>
>> ---
>>
>> drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> index 38e88071363..0ee440216b8 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> @@ -805,7 +805,8 @@ static void dw_mipi_dsi_bridge_post_disable(struct
>> drm_bridge *bridge)
>> * This needs to be fixed in the drm_bridge framework and the API
>> * needs to be updated to manage our own call chains...
>> */
>> -dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
>> +if (dsi->panel_bridge->funcs->post_disable)
>> +dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
>>
>
> Why not drm_bridge_post_disable ?
Ah - that seems like a nicer fix! Do you think the comment above
describing why this function pointer is called directly can be removed
as well if we go this route?
If someone calls drm_bridge_post_disable() on the Synposys DSI
drm_bridge it will go on to call post_disable on all other bridges in
the chain, in addition to us calling them here. Is it an issue to call
it multiple times?
Thanks,
Matt
>
>
> Regards
>
> Andrzej
>
>
>> if (dsi->slave) {
>> dw_mipi_dsi_disable(dsi->slave);
>
>
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Re: [PATCH] drm/bridge/synopsys: dsi: Don't blindly call post_disable
On 24.04.2019 16:22, Matt Redfearn wrote:
> The DRM documentation states that post_disable is an optional callback.
> As such an implementing device may not populate it. To avoid panicing
> the kernel by calling a NULL function pointer, we should NULL check it
> before blindy calling it.
>
> Signed-off-by: Matt Redfearn
> ---
>
> drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> index 38e88071363..0ee440216b8 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> @@ -805,7 +805,8 @@ static void dw_mipi_dsi_bridge_post_disable(struct
> drm_bridge *bridge)
>* This needs to be fixed in the drm_bridge framework and the API
>* needs to be updated to manage our own call chains...
>*/
> - dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
> + if (dsi->panel_bridge->funcs->post_disable)
> + dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
>
Why not drm_bridge_post_disable ?
Regards
Andrzej
> if (dsi->slave) {
> dw_mipi_dsi_disable(dsi->slave);
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Re: [PATCH] drm/bridge/synopsys: dsi: Don't blindly call post_disable
Hi Matt,
Thank you for the patch.
On Wed, Apr 24, 2019 at 02:22:00PM +, Matt Redfearn wrote:
> The DRM documentation states that post_disable is an optional callback.
> As such an implementing device may not populate it. To avoid panicing
> the kernel by calling a NULL function pointer, we should NULL check it
> before blindy calling it.
>
> Signed-off-by: Matt Redfearn
Reviewed-by: Laurent Pinchart
> ---
>
> drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> index 38e88071363..0ee440216b8 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
> @@ -805,7 +805,8 @@ static void dw_mipi_dsi_bridge_post_disable(struct
> drm_bridge *bridge)
>* This needs to be fixed in the drm_bridge framework and the API
>* needs to be updated to manage our own call chains...
>*/
> - dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
> + if (dsi->panel_bridge->funcs->post_disable)
> + dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
>
> if (dsi->slave) {
> dw_mipi_dsi_disable(dsi->slave);
--
Regards,
Laurent Pinchart
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[PATCH] drm/bridge/synopsys: dsi: Don't blindly call post_disable
The DRM documentation states that post_disable is an optional callback.
As such an implementing device may not populate it. To avoid panicing
the kernel by calling a NULL function pointer, we should NULL check it
before blindy calling it.
Signed-off-by: Matt Redfearn
---
drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
index 38e88071363..0ee440216b8 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
@@ -805,7 +805,8 @@ static void dw_mipi_dsi_bridge_post_disable(struct
drm_bridge *bridge)
* This needs to be fixed in the drm_bridge framework and the API
* needs to be updated to manage our own call chains...
*/
- dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
+ if (dsi->panel_bridge->funcs->post_disable)
+ dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
if (dsi->slave) {
dw_mipi_dsi_disable(dsi->slave);
--
2.17.1
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