Re: [PATCH AUTOSEL 5.15 123/188] drm/tegra: dc: rgb: Allow changing PLLD rate on Tegra30+

From: Sasha Levin
Date: Sat Jan 22 2022 - 14:19:44 EST


On Tue, Jan 18, 2022 at 12:39:43PM +0300, Dmitry Osipenko wrote:
18.01.2022 12:37, Dmitry Osipenko пишет:
18.01.2022 05:30, Sasha Levin пишет:
From: Dmitry Osipenko <digetx@xxxxxxxxx>

[ Upstream commit 0c921b6d4ba06bc899fd84d3ce1c1afd3d00bc1c ]

Asus Transformer TF700T is a Tegra30 tablet device which uses RGB->DSI
bridge that requires a precise clock rate in order to operate properly.
Tegra30 has a dedicated PLL for each display controller, hence the PLL
rate can be changed freely. Allow PLL rate changes on Tegra30+ for RGB
output. Configure the clock rate before display controller is enabled
since DC itself may be running off this PLL and it's not okay to change
the rate of the active PLL that doesn't support dynamic frequency
switching since hardware will hang.

Tested-by: Maxim Schwalm <maxim.schwalm@xxxxxxxxx> #TF700T
Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/gpu/drm/tegra/dc.c | 27 ++++++++++++--------
drivers/gpu/drm/tegra/dc.h | 1 +
drivers/gpu/drm/tegra/rgb.c | 49 +++++++++++++++++++++++++++++++++++--
3 files changed, 65 insertions(+), 12 deletions(-)

Hi,

This patch shouldn't be ported to any stable kernel because h/w that
needs this patch was just merged to the 5.17.

* support of h/w that needs..

I'll drop it, thanks!

--
Thanks,
Sasha