Re: GPMI iMX6ull timeout on DMA

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Michael,

Michael Nazzareno Trimarchi <michael@amarulasolutions.com> wrote on
Mon, 1 Feb 2021 16:08:23 +0100:

> Hi
> 
> On Mon, Feb 1, 2021 at 3:32 PM Michael Nazzareno Trimarchi
> <michael@amarulasolutions.com> wrote:
> >
> > Hi
> >
> > On Mon, Feb 1, 2021 at 3:13 PM Miquel Raynal <miquel.raynal@bootlin.com> wrote:  
> > >
> > > Hi Michael,
> > >
> > > Michael Nazzareno Trimarchi <michael@amarulasolutions.com> wrote on
> > > Sat, 30 Jan 2021 10:41:29 +0100:
> > >  
> > > > Hi Miquel
> > > >
> > > > commit f8e6ad14388067f91b26d044185d95623fbc9535
> > > > Author: Michael Trimarchi <michael@amarulasolutions.com>
> > > > Date:   Fri Jan 29 08:46:53 2021 +0100
> > > >
> > > >     mtd: nand: Calculate the clock before enable it
> > > >
> > > >     Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
> > > >     Change-Id: I79b0da39de0a9b32ea0b002fa200d7f44d4f8ce7
> > > >
> > > > diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c
> > > > b/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c
> > > > index 322a008290e5..0bca52b3bc8f 100644
> > > > --- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c
> > > > +++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c
> > > > @@ -377,6 +377,7 @@ static void gpmi_nfc_compute_timings(struct
> > > > gpmi_nand_data *this,
> > > >                                      const struct nand_sdr_timings *sdr)
> > > >  {
> > > >         struct gpmi_nfc_hardware_timing *hw = &this->hw;
> > > > +       struct resources *r = &this->resources;
> > > >         unsigned int dll_threshold_ps = this->devdata->max_chain_delay;
> > > >         unsigned int period_ps, reference_period_ps;
> > > >         unsigned int data_setup_cycles, data_hold_cycles, addr_setup_cycles;
> > > > @@ -440,6 +441,8 @@ static void gpmi_nfc_compute_timings(struct
> > > > gpmi_nand_data *this,
> > > >                 hw->ctrl1n |= BF_GPMI_CTRL1_RDN_DELAY(sample_delay_factor) |
> > > >                               BM_GPMI_CTRL1_DLL_ENABLE |
> > > >                               (use_half_period ? BM_GPMI_CTRL1_HALF_PERIOD : 0);
> > > > +
> > > > +       clk_set_rate(r->clock[0], hw->clk_rate);
> > > >  }
> > > >
> > > >  void gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
> > > > @@ -449,8 +452,6 @@ void gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
> > > >         void __iomem *gpmi_regs = r->gpmi_regs;
> > > >         unsigned int dll_wait_time_us;
> > > >
> > > > -       clk_set_rate(r->clock[0], hw->clk_rate);
> > > > -
> > > >         writel(hw->timing0, gpmi_regs + HW_GPMI_TIMING0);
> > > >         writel(hw->timing1, gpmi_regs + HW_GPMI_TIMING1);
> > > >
> > > > Right now I have this change applied and seems fine. That is the only
> > > > difference I get. Clock is apply a bit earlier that when is enabled
> > > > it.  
> > >
> > > This is very interesting. So this would mean the issue you are
> > > experiencing comes from the clock driver which kind of returns too
> > > early from clk_set_rate()? Could you report this to the clk ML/NXP clk
> > > maintainers and keep us in copy? If it is as global as it sounds, we
> > > might not be the only ones affected.
> > >  
> >
> > The imx28 is broken too, so it's a general problem. I need to trace it down
> > I have a reverting for lts but it\s not the way to go
> >  
> 
> For imx28 you ask to set the rate to 22Mhz but you don't care about the clock
> that you get back. You get back 12Mhz because the base clock is 24 Mhz and seems
> that it can not get the point. You need to check if the clock
> requested is in range or ask
> for set_rate_clk_min to avoid to have somenthing lower. Then for
> imx6ull because is sporadic
> I think that is more connected to the clk_set_rate and when you change
> the register. Can not be a
> setting time?

So, if I understand correctly, we face two different problems:
- imx6*: seems like a clock issue regarding the clock settlement
- imx28: actual NAND driver issue (does not check the validity of the
  new frequency). This should be handled properly in
  ->setup_interface().

Thanks,
Miquèl

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