Quoting Marijn Suijten (2021-08-30 15:45:42)

Hi Stephen,

On 2021-08-30 15:16:13, Stephen Boyd wrote:

quoted

Quoting Marijn Suijten (2021-08-30 11:24:44)

quoted

All DSI PHY/PLL drivers were referencing their VCO parent clock by a
global name, most of which don't exist or have been renamed.  These
clock drivers seem to function fine without that except the 14nm driver
for the sdm6xx [1].

At the same time all DTs provide a "ref" clock as per the requirements
of dsi-phy-common.yaml, but the clock is never used.  This patchset puts
that clock to use without relying on a global clock name, so that all
dependencies are explicitly defined in DT (the firmware) in the end.

Note that msm8974 is the only board not providing this clock, and
apq8064 was providing the wrong clock (19.2MHz cxo instead of 27MHz
pxo).  Both have been been addressed in separate patches that are
supposed to land well in advance of this patchset.

Furthermore not all board-DTs provided this clock initially but that
deficiency has been addressed in followup patches (see the Fixes:
below).  Those commits seem to assume that the clock was used, while
nothing in history indicates that this "ref" clock was ever retrieved.

[1]: https://lore.kernel.org/linux-arm-msm/386db1a6-a1cd-3c7d-a88e-dc83f8a1be96@somainline.org/ (local)

Fixes: 79e51645a1dd ("arm64: dts: qcom: msm8916: Set 'xo_board' as ref clock of the DSI PHY")
Fixes: 6969d1d9c615 ("ARM: dts: qcom-apq8064: Set 'cxo_board' as ref clock of the DSI PHY")
Fixes: 0c0e72705a33 ("arm64: dts: sdm845: Set 'bi_tcxo' as ref clock of the DSI PHYs")
Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org>
---
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c      | 4 +++-
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_14nm.c      | 4 +++-
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm.c      | 4 +++-
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_28nm_8960.c | 4 +++-
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c       | 4 +++-
 5 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c
index e46b10fc793a..3cbb1f1475e8 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_10nm.c

@@ -562,7 +562,9 @@ static int pll_10nm_register(struct dsi_pll_10nm *pll_10nm, struct clk_hw **prov
        char clk_name[32], parent[32], vco_name[32];
        char parent2[32], parent3[32], parent4[32];
        struct clk_init_data vco_init = {
-               .parent_names = (const char *[]){ "xo" },
+               .parent_data = &(const struct clk_parent_data) {
+                       .fw_name = "ref",

Please also add .name as the old parent_names value so that newer
kernels can be used without having to use new DT.

We discussed that only msm8974 misses this "ref" clock at the time of
writing.  Aforementioned Fixes: patches have all been merged about 3
years ago, are those DTs still in use with a newer kernel?  I suppose
this patch is only backported to kernels including those DT patches, is
it reasonable to assume that at least that DT is in use there?

I have no idea.

Besides, not all clock trees provide this global "xo" or "bi_tcxo" clock
in the first place.

It doesn't hurt to also specify a .name to help migrate anything else
over. Unless you're confident it won't cause problems to rely on proper
DT being used?