Re: [PATCH 07/13] mtd: rawnand: gpmi: set aggregate ready/busy signalling

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

Hello Han,

Could we have your input on this patch, please?

On Thu, 26 Apr 2018 17:41:28 +0200, Sam Lefebvre
<sam.lefebvre@essensium.com> wrote:

> The GPMI block by default decouples the ready/busy signal (which is
> shared between all chip-selects) to separate internal signals per
> chip-select. However, since the gpmi-nand driver uses DMA0 for all
> chip-selects, DMA transfers will not be able to see the ready/busy
> status for any chip-select other than 0.
> 
> Currently, this happens to work because nand_command() ends with an
> explicit nand_wait_ready() and the driver only sets up a single command
> in a DMA chain. nand_wait_ready() polls for the chip-select specific
> ready/busy status bit. Future patches, however, will set up a DMA chain
> with several commands, so these will have to wait correctly in the DMA
> chain itself.
> 
> To fix this, set the GANGED_RDYBUSY bit in the control1 register. This
> ties all internal ready/busy signals together, so DMA0 will also see
> the ready/busy status of chip selects 1-2-3. It's a bit silly that this
> isn't implied in hardware by the DECOUPLE_CS bit.
> 
> Signed-off-by: Sam Lefebvre <sam.lefebvre@essensium.com>
> Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
> Cc: Han Xu <han.xu@nxp.com>
> ---
> Tested on an i.MX6Q with two identical chips on CS0 and CS1.
> ---
>  drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c  | 3 +++
>  drivers/mtd/nand/raw/gpmi-nand/gpmi-regs.h | 1 +
>  2 files changed, 4 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c b/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c
> index 83697b8df871..1858afdb400d 100644
> --- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c
> +++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c
> @@ -193,6 +193,9 @@ int gpmi_init(struct gpmi_nand_data *this)
>  	 */
>  	writel(BM_GPMI_CTRL1_DECOUPLE_CS, r->gpmi_regs + HW_GPMI_CTRL1_SET);
>  
> +	/* Aggregate ready busy signalling. */
> +	writel(BM_GPMI_CTRL1_GANGED_RDYBUSY, r->gpmi_regs + HW_GPMI_CTRL1_SET);
> +
>  	gpmi_disable_clk(this);
>  	return 0;
>  err_out:
> diff --git a/drivers/mtd/nand/raw/gpmi-nand/gpmi-regs.h b/drivers/mtd/nand/raw/gpmi-nand/gpmi-regs.h
> index d92bf32221ca..e341802c90ac 100644
> --- a/drivers/mtd/nand/raw/gpmi-nand/gpmi-regs.h
> +++ b/drivers/mtd/nand/raw/gpmi-nand/gpmi-regs.h
> @@ -120,6 +120,7 @@
>  #define BV_GPMI_CTRL1_WRN_DLY_SEL_7_TO_12NS		0x2
>  #define BV_GPMI_CTRL1_WRN_DLY_SEL_NO_DELAY		0x3
>  
> +#define BM_GPMI_CTRL1_GANGED_RDYBUSY		(1 << 19)
>  #define BM_GPMI_CTRL1_BCH_MODE				(1 << 18)
>  
>  #define BP_GPMI_CTRL1_DLL_ENABLE			17

Thanks,
Miquèl