On Fri, Oct 30, 2020 at 01:51:49PM +0100, Sylwester Nawrocki wrote: > This patch adds interconnect support to exynos-mixer. The mixer works > the same as before when CONFIG_INTERCONNECT is 'n'. > > For proper operation of the video mixer block we need to ensure the > interconnect busses like DMC or LEFTBUS provide enough bandwidth so > as to avoid DMA buffer underruns in the mixer block. I.e we need to > prevent those busses from operating in low perfomance OPPs when > the mixer is running. > In this patch the bus bandwidth request is done through the interconnect > API, the bandwidth value is calculated from selected DRM mode, i.e. > video plane width, height, refresh rate and pixel format. > > The bandwidth setting is synchronized with VSYNC when we are switching > to lower bandwidth. This is required to ensure enough bandwidth for > the device since new settings are normally being applied in the hardware > synchronously with VSYNC. > > Co-developed-by: Artur Świgoń <a.swigon@xxxxxxxxxxx> > Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > Signed-off-by: Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx> > --- > Changes for v7: > - fixed incorrect setting of the ICC bandwidth when the mixer is > disabled, now the bandwidth is set explicitly to 0 in such case. > > Changes for v6: > - the icc_set_bw() call is now only done when calculated value for > a crtc changes, this avoids unnecessary calls per each video frame > - added synchronization of the interconnect bandwidth setting with > the mixer VSYNC in order to avoid buffer underflow when we lower > the interconnect bandwidth when the hardware still operates with > previous mode settings that require higher bandwidth. This fixed > IOMMU faults observed e.g. during switching from two planes to > a single plane operation. > > Changes for v5: > - renamed soc_path variable to icc_path > --- > drivers/gpu/drm/exynos/exynos_mixer.c | 146 ++++++++++++++++++++++++++++++++-- > 1 file changed, 138 insertions(+), 8 deletions(-) [...] > @@ -1223,19 +1330,33 @@ static int mixer_probe(struct platform_device *pdev) > struct device *dev = &pdev->dev; > const struct mixer_drv_data *drv; > struct mixer_context *ctx; > + struct icc_path *path; > int ret; > > + /* > + * Returns NULL if CONFIG_INTERCONNECT is disabled. You could add here: or if "interconnects" property does not exist. Best regards, Krzysztof
