[RFC PATCH 2/2] gpmi-nand: Add ERR007117 protection for nfc_apply_timings

[Christian Eggers]

On Tuesday, 12 October 2021, 11:02:24 CEST, Stefan Riedmueller wrote:
> According to i.MX 6 erratum ERR007117 gpmi clocks need to be gated off
> when doing a gpmi_io clk rate change. So gate the clocks off before
> the rate change in nfc_apply_timings and ungate them again after the
> change.
> 
> Otherwise this rate change can lead to an unresponsive GPMI core which
> results in DMA timeouts and failed driver probe:
> 
> [    4.072318] gpmi-nand 112000.gpmi-nand: DMA timeout, last DMA
> ...
> [    4.370355] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -110
> ...
> [    4.375988] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -22
> [    4.381524] gpmi-nand 112000.gpmi-nand: Error in ECC-based read: -22
> [    4.387988] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -22
> [    4.393535] gpmi-nand 112000.gpmi-nand: Chip: 0, Error -22
> ...
> 
> Signed-off-by: Stefan Riedmueller <s.riedmueller at phytec.de>
> ---
> Hi,
Hi Stefan,

thanks for providing the patches! I am suffering from this problem for some
time now and I am happy to get this fixed!

> 
> I'm not sure about the error handling here, if it is actually neccessary.
> So some feedback would be nice here.

IMHO errors should always be handled.

> 
> Thanks,
> Stefan
> ---
>  drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
> index a1f7000f033e..326c8a895f1f 100644
> --- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
> +++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-nand.c
> @@ -713,15 +713,28 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this,
>  			      (use_half_period ? BM_GPMI_CTRL1_HALF_PERIOD : 0);
>  }
>  
> -static void gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
> +static int gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
>  {
>  	struct gpmi_nfc_hardware_timing *hw = &this->hw;
>  	struct resources *r = &this->resources;
>  	void __iomem *gpmi_regs = r->gpmi_regs;
>  	unsigned int dll_wait_time_us;
> +	int ret;
> +
> +	if (GPMI_IS_MX6Q(this)) {
I would like to explicitly see i.MX6UL(L) here (in order to make clear that
not only Solo/Dual/Quad are affected):
#define GPMI_IS_MX6UL(x)		((x)->devdata->type == IS_MX6Q)
...
if (GPMI_IS_MX6Q(this) || GPMI_IS_MX6UL(this)) {

But if Han Xu is sure that also SoloX and i.MX7 are affected, GPMI_IS_MX6(x)
is fine for me. In this case I would like to explicitly mention this in the 
commit message, so that nobody will change this later because ERR007117
exists only for Solo/Dual/Quad.

> +		ret = __gpmi_enable_clk(this, false);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	clk_set_rate(r->clock[0], hw->clk_rate);
>  
> +	if (GPMI_IS_MX6Q(this)) {
> +		ret = __gpmi_enable_clk(this, true);
> +		if (ret)
> +			return ret;
> +	}
> +
>  	writel(hw->timing0, gpmi_regs + HW_GPMI_TIMING0);
>  	writel(hw->timing1, gpmi_regs + HW_GPMI_TIMING1);
>  
> @@ -739,6 +752,8 @@ static void gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
>  
>  	/* Wait for the DLL to settle. */
>  	udelay(dll_wait_time_us);
> +
> +	return 0;
>  }
>  
>  static int gpmi_setup_interface(struct nand_chip *chip, int chipnr,
> @@ -2271,7 +2286,9 @@ static int gpmi_nfc_exec_op(struct nand_chip *chip,
>  	 */
>  	if (this->hw.must_apply_timings) {
>  		this->hw.must_apply_timings = false;
> -		gpmi_nfc_apply_timings(this);
> +		ret = gpmi_nfc_apply_timings(this);
> +		if (ret)
> +			return ret;
>  	}
>  
>  	dev_dbg(this->dev, "%s: %d instructions\n", __func__, op->ninstrs);
> 

Tested-by: Christian Eggers <ceggers at arri.de>  # on i.MX6ULL with MT29F4G08ABADAH4
Cc: stable at vger.kernel.org