On Sat, Jul 16, 2022 at 12:31:45PM +0200, Xavier Drudis Ferran wrote:
The original code set up the DDR clock to 48 MHz, not 50MHz as requested, and did it in a way that didn't satisfy the Application Notes in RK3399 TRM [1]. 2.9.2.B says:
PLL frequency range requirement [...] FOUTVCO: 800MHz to 3.2GHz
2.9.2.A : PLL output frequency configuration [...] FOUTVCO = FREF / REFDIV * FBDIV FOUTPOSTDIV = FOUTVCO / POSTDIV1 / POSTDIV2
FREF = 24 MHz
The original code gives FOUTVCO: 24MHz/1 * 12 = 288MHz < 800MHz And the resulting FOUTPOSTDIV is 288MHz / 3 / 2 = 48MHz but the requested frequency was 50MHz
Note: 2.7.2 Detail Register Description PMUCRU_PPLL_CON0 says
fbdiv Feedback Divide Value Valid divider settings are: [16, 3200] in integer mode
So .fbdiv = 12 wouldn't be right. But 2.9.2.C says:
PLL setting consideration [...] The following settings are valid for FBDIV: DSMPD=1 (Integer Mode): 12,13,14,16-4095 (practical value is limited to 3200, 2400, or 1600 (FVCOMAX / FREFMIN)) [...]
So .fbdiv = 12 would be right.
In any case FOUTVCO is still wrong. I thank YouMin Chen for confirmation and explanation.
Despite documentation, I don't seem to be able to reproduce a practical problem with the wrong FOUTVCO. When I initially found it I thought some problems with detecting the RAM capacity in my Rock Pi 4B could be related to it and my patch seemed to help. But since I'm no longer able to reproduce the issue, it works with or without this patch. And meanwhile a patch[2] by Lee Jones and YouMin Chen addresses this issue. Btw, shouldn't that be commited?
So this patches solves no visible problem. Yet, to prevent future problems, I think it'd be best to stick to spec.
An alternative to this patch could be
{.refdiv = 1, .fbdiv = 75, .postdiv1 = 6, .postdiv2 = 6};This would theoretically consume more power and yield less jitter, according to 2.9.2.C :
PLL setting consideration [...] For lowest power operation, the minimum VCO and FREF frequencies should be used. For minimum jitter operation, the highest VCO and FREF frequencies should be used. [...]
But I haven't tried it because I don't think it matters much. 50MHz for DDR is only shortly used by TPL at RAM init. Normal operation is at 800MHz. Maybe it's better to use less power until later when more complex software can control batteries or charging or whatever ?
Cc: Simon Glass sjg@chromium.org Cc: Philipp Tomsich philipp.tomsich@vrull.eu Cc: Kever Yang kever.yang@rock-chips.com Cc: Lukasz Majewski lukma@denx.de Cc: Sean Anderson seanga2@gmail.com
Link: [1] https://www.rockchip.fr/Rockchip%20RK3399%20TRM%20V1.4%20Part1.pdf
Link: [2] https://patchwork.ozlabs.org/project/uboot/list/?series=305766
Signed-off-by: Xavier Drudis Ferran xdrudis@tinet.cat
The incorrect clock settings trigger an assert and prevent the board from booting when clock debugging is enabled.
Fix works for me on Pinebook Pro.
Thanks
Michal
Tested-by: Michal Suchánek msuchanek@suse.de
drivers/clk/rockchip/clk_rk3399.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/clk/rockchip/clk_rk3399.c b/drivers/clk/rockchip/clk_rk3399.c index 7d31a9f22a..4762462b04 100644 --- a/drivers/clk/rockchip/clk_rk3399.c +++ b/drivers/clk/rockchip/clk_rk3399.c @@ -840,7 +840,7 @@ static ulong rk3399_ddr_set_clk(struct rockchip_cru *cru, switch (set_rate) { case 50 * MHz: dpll_cfg = (struct pll_div)
{.refdiv = 1, .fbdiv = 12, .postdiv1 = 3, .postdiv2 = 2};
{.refdiv = 2, .fbdiv = 75, .postdiv1 = 3, .postdiv2 = 6};-- 2.20.1