Hello Peng, On 30.09.24 08:38, Peng Fan wrote: >> Subject: i.MX8/9: question about unused DDR PHY trained CSR board >> array >> Looking at the DDR setup code for i.MX8M and i.MX9 that you had >> contributed, I am wondering about struct >> dram_cfg_param::ddrphy_trained_csr and the global >> ddrphy_trained_csr array. >> >> struct dram_cfg_param::ddrphy_trained_csr is presumably generated >> by the i.MX DDR tool and it seems populated by all the i.MX8M/9 >> boards in U-Boot. >> >> This struct member is wholly unused though and instead a global >> ddrphy_trained_csr is used. >> >> What I wonder about is whether it's possible for the DDR tool to >> generate a different ddrphy_trained_csr than the default: >> >> 1) If yes, we should drop the global ddrphy_trained_csr and actually >> use >> the board-specific array >> >> 2) If not, we should drop the board-specific array and perhaps ask for >> the DDR tool to be changed >> >> I initially assumed 1) and because all boards supported by barebox had >> a board-specific ddrphy_trained_csr that's identical to the global >> ddrphy_trained_csr, I dropped the unused array[1][2]. >> >> I now have the DDR settings for an i.MX9 LPDDR4 board in front of me >> that has different contents for struct >> dram_cfg_param::ddrphy_trained_csr than the default. >> >> I will inquire how that came about, but in parallel I wanted to ask you if >> this is supposed to happen and to alert you to this issue. > > Thanks for raising this issue. I think board specific csr should be used. > > I will check with DDR TOOL owners on this. Did you hear back in the meantime? Thanks, Ahmad > >> >> The way things are, this is either a bug or a missed space saving >> opportunity for U-Boot. > > Thanks, > Peng. > > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
