On Mon, Aug 5, 2019 at 7:10 PM Ondřej Jirman <megous@xxxxxxxxxx> wrote: > > On Mon, Aug 05, 2019 at 06:54:17PM +0800, Chen-Yu Tsai wrote: > > On Mon, Aug 5, 2019 at 6:45 PM Ondřej Jirman <megous@xxxxxxxxxx> wrote: > > > > > > On Mon, Aug 05, 2019 at 06:16:14PM +0800, Chen-Yu Tsai wrote: > > > > On Fri, Apr 12, 2019 at 8:07 PM megous via linux-sunxi > > > > <linux-sunxi@xxxxxxxxxxxxxxxx> wrote: > > > > > > > > > > From: Ondrej Jirman <megous@xxxxxxxxxx> > > > > > > > > > > RTC on H6 is mostly the same as on H5 and H3. It has slight differences > > > > > mostly in features that are not yet supported by this driver. > > > > > > > > > > Some differences are already stated in the comments in existing code. > > > > > One other difference is that H6 has extra bit in LOSC_CTRL_REG, called > > > > > EXT_LOSC_EN to enable/disable external low speed crystal oscillator. > > > > > > > > > > It also has bit EXT_LOSC_STA in LOSC_AUTO_SWT_STA_REG, to check whether > > > > > external low speed oscillator is working correctly. > > > > > > > > > > This patch adds support for enabling LOSC when necessary: > > > > > > > > > > - during reparenting > > > > > - when probing the clock > > > > > > > > > > H6 also has capacbility to automatically reparent RTC clock from > > > > > external crystal oscillator, to internal RC oscillator, if external > > > > > oscillator fails. This is enabled by default. Disable it during > > > > > probe. > > > > > > > > > > Signed-off-by: Ondrej Jirman <megous@xxxxxxxxxx> > > > > > --- > > > > > drivers/rtc/rtc-sun6i.c | 40 ++++++++++++++++++++++++++++++++++++++-- > > > > > 1 file changed, 38 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/drivers/rtc/rtc-sun6i.c b/drivers/rtc/rtc-sun6i.c > > > > > index 11f56de52179..7375a530c565 100644 > > > > > --- a/drivers/rtc/rtc-sun6i.c > > > > > +++ b/drivers/rtc/rtc-sun6i.c > > > > > @@ -41,9 +41,11 @@ > > > > > /* Control register */ > > > > > #define SUN6I_LOSC_CTRL 0x0000 > > > > > #define SUN6I_LOSC_CTRL_KEY (0x16aa << 16) > > > > > +#define SUN6I_LOSC_CTRL_AUTO_SWT_BYPASS BIT(15) > > > > > > > > Manual says bit 14? Or is this different from LOSC_AUTO_SWT_EN? > > > > > > > > The rest looks ok. > > > > > > To give you more information. This is a new thing in H6 BSP, compared > > > to BSPs for previous SoCs (H5/H3). > > > > > > 20 #define REG_CLK32K_AUTO_SWT_EN BIT(14) > > > 21 #define REG_CLK32K_AUTO_SWT_BYPASS BIT(15) > > > > > > Init sequence changed in H6 BSP to: > > > > > > 646 /* > > > 647 * Step1: select RTC clock source > > > 648 */ > > > 649 tmp_data = readl(chip->base + SUNXI_LOSC_CTRL); > > > 650 tmp_data &= (~REG_CLK32K_AUTO_SWT_EN); > > > 651 > > > 652 /* Disable auto switch function */ > > > 653 tmp_data |= REG_CLK32K_AUTO_SWT_BYPASS; > > > 654 writel(tmp_data, chip->base + SUNXI_LOSC_CTRL); > > > 655 > > > 656 tmp_data = readl(chip->base + SUNXI_LOSC_CTRL); > > > 657 tmp_data |= (RTC_SOURCE_EXTERNAL | REG_LOSCCTRL_MAGIC); > > > 658 writel(tmp_data, chip->base + SUNXI_LOSC_CTRL); > > > 659 > > > 660 /* We need to set GSM after change clock source */ > > > 661 udelay(10); > > > 662 tmp_data = readl(chip->base + SUNXI_LOSC_CTRL); > > > 663 tmp_data |= (EXT_LOSC_GSM | REG_LOSCCTRL_MAGIC); > > > 664 writel(tmp_data, chip->base + SUNXI_LOSC_CTRL); > > > 665 > > > > I don't have this in my H6 BSPs. One is H6 Lichee v1.1 downloaded from Pine64. > > The link was from linux-sunxi wiki's H6 page. > > > > The other is a 4.9 kernel tree, which I believe is from Allwinner's github: > > > > https://github.com/Allwinner-Homlet/H6-BSP4.9-linux > > Interesting. :) I have the BSP I was using saved here: > > https://megous.com/git/linux/tree/drivers/rtc/rtc-sunxi.c?h=h6-4.9-bsp#n649 > > It's based of 4.9.119 > > https://megous.com/git/linux/log/?h=h6-4.9-bsp > > I don't remember where I found it. But I imported it fairly recently, and > the code you pointed to looks like an older version that I can found in some > beta H6 BSP, that I imported way earlier and is based on 4.9.56: > > https://megous.com/git/linux/tree/drivers/rtc/rtc-sunxi.c?h=linux-h6 > https://megous.com/git/linux/log/?h=linux-h6 > > Hmm, archeology. :) That's good enough for me. I suppose if we do have any more doubts we could ask them directly. Reviewed-by: Chen-Yu Tsai <wens@xxxxxxxx> > > > For older BSPs, the init sequence looked like this: > > > > > > 482 /* > > > 483 * Step1: select RTC clock source > > > 484 */ > > > 485 tmp_data = sunxi_rtc_read(SUNXI_LOSC_CTRL_REG); > > > 486 tmp_data &= (~REG_CLK32K_AUTO_SWT_EN); > > > 487 tmp_data |= (RTC_SOURCE_EXTERNAL | REG_LOSCCTRL_MAGIC); > > > 488 tmp_data |= (EXT_LOSC_GSM); > > > 489 sunxi_rtc_write(tmp_data, SUNXI_LOSC_CTRL_REG); > > > 490 > > > > > > EXT_LOSC_GSM has values 4 values from low to high, and I guess it configures > > > gain for the oscillator's amplifier in the feedback loop of the circuit. > > > > > > So the new code, for some reason changed from single write to sequence > > > of individual writes/config steps: > > > > > > 1) disable auto-switch and enable auto-switch bypass > > > 2) select RTC clock source (to LOSC) > > > (wait) > > > > Maybe it's possible to glitch if these two are combined? > > That's what I thought too. Or the programmer thought so, and was just > programming defensively, and there's no real problem in the practice. > > But that specific delay() seems like someone trying to solve a real issue. Of > course there's no knowing if it was on H6 or on some other SoC. It's probably for the clock waveform to stabilize. Why they do it _after_ switching to the clock is weird though. > regards, > o. > > > > > > 3) configure gain on the LOSC > > > > > > regards, > > > o. > > > > > > > ChenYu > > > > > > -- > > > You received this message because you are subscribed to the Google Groups "linux-sunxi" group. > > > To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscribe@xxxxxxxxxxxxxxxx. > > > To view this discussion on the web, visit https://groups.google.com/d/msgid/linux-sunxi/20190805104529.z3mex3m2tss7lzlr%40core.my.home. > > -- > You received this message because you are subscribed to the Google Groups "linux-sunxi" group. > To unsubscribe from this group and stop receiving emails from it, send an email to linux-sunxi+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web, visit https://groups.google.com/d/msgid/linux-sunxi/20190805111037.76vmanzcurffpbdf%40core.my.home.
