On Mon, Aug 30, 2021 at 05:18:37PM +0300, Dmitry Baryshkov wrote: > On Mon, 30 Aug 2021 at 17:14, Marijn Suijten > <marijn.suijten@xxxxxxxxxxxxxx> wrote: > > > > On Mon, Aug 30, 2021 at 04:24:58PM +0300, Dmitry Baryshkov wrote: > > > On Mon, 30 Aug 2021 at 11:28, Marijn Suijten > > > <marijn.suijten@xxxxxxxxxxxxxx> wrote: > > > > > > > > Hi Dmitry, > > > > > > > > On 8/30/21 3:18 AM, Dmitry Baryshkov wrote: > > > > > On Sun, 29 Aug 2021 at 23:30, Marijn Suijten > > > > > <marijn.suijten@xxxxxxxxxxxxxx> wrote: > > > > >> > > > > >> The 28NM DSI PLL driver for msm8960 calculates with a 27MHz reference > > > > >> clock and should hence use PXO, not CXO which runs at 19.2MHz. > > > > >> > > > > >> Note that none of the DSI PHY/PLL drivers currently use this "ref" > > > > >> clock; they all rely on (sometimes inexistant) global clock names and > > > > >> usually function normally without a parent clock. This discrepancy will > > > > >> be corrected in a future patch, for which this change needs to be in > > > > >> place first. > > > > >> > > > > >> Cc: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > > > > >> Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx> > > > > > > > > > > Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > > > > > > > > > > Checked the downstream driver, it always uses 27 MHz clock in calculations. > > > > > > > > > > > > Given our concerns for msm8974 not updating DT in parallel with the > > > > kernel (hence the need for a global-name fallback because "ref" is > > > > missing from the DT), should we worry about the same for apq8064? That > > > > is, is there a chance that the kernel but not the firmware is upgraded > > > > leading to the wrong parent clock being used? The msm8960 variant of > > > > the 28nm PLL driver uses parent_rate in a few places and might read > > > > cxo's 19.2MHz erroneously instead of using pxo's 27MHz. > > > > > > Checked the code. It uses .parent_names = "pxo", so changing ref > > > clock should not matter. We'd need to fix ref clocks and after that we > > > can switch parent names to fw_name. > > > > Correct, hence why this patch is ordered before the switch to .fw_name. > > These patches can't go in the same series if apq8064 doesn't update its > > firmware in parallel with the kernel just like msm8974. Do you know if > > this is the case? If so, how much time do you think should be between > > the DT fix (this patch) and migrating the drivers? > > You can have parent_data with .fw_name and .name in it. .name will be > used as a fallback if .fw_name doesn't match. The problem is that it will always find the "ref" clock which references &cxo_board until the DT is updated with this patch to use &pxo_board instead. Question is, will the kernel and DT usually/always be updated in parallel? - Marijn
