Re: [RFC PATCH v1] mtd: rawnand: meson: invalidate cache on polling ECC bit

[Arseniy Krasnov]

Hello,

we reproduced this problem on one of our boards. It triggers very rare
when 'usleep_range()' is present, but when sleeping is removed - it fires
always. I suppose problem is with caching, as 'info_buf' memory is mapped by
'dma_map_single()'.

Thanks, Arseniy

On 13.03.2023 10:32, Arseniy Krasnov wrote:
> 'info_buf' memory is cached and driver polls ECC bit in it. This bit
> is set by the NAND controller. If 'usleep_range()' returns before device
> sets this bit, 'info_buf' will be cached and driver won't see update of
> this bit and will loop forever.
> 
> Fixes: 8fae856c5350 ("mtd: rawnand: meson: add support for Amlogic NAND flash controller")
> Signed-off-by: Arseniy Krasnov <AVKrasnov@xxxxxxxxxxxxxx>
> ---
>  drivers/mtd/nand/raw/meson_nand.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/raw/meson_nand.c b/drivers/mtd/nand/raw/meson_nand.c
> index 5ee01231ac4c..2c05c08a0eaf 100644
> --- a/drivers/mtd/nand/raw/meson_nand.c
> +++ b/drivers/mtd/nand/raw/meson_nand.c
> @@ -176,6 +176,7 @@ struct meson_nfc {
>  
>  	dma_addr_t daddr;
>  	dma_addr_t iaddr;
> +	u32 info_bytes;
>  
>  	unsigned long assigned_cs;
>  };
> @@ -503,6 +504,7 @@ static int meson_nfc_dma_buffer_setup(struct nand_chip *nand, void *databuf,
>  					 nfc->daddr, datalen, dir);
>  			return ret;
>  		}
> +		nfc->info_bytes = infolen;
>  		cmd = GENCMDIADDRL(NFC_CMD_AIL, nfc->iaddr);
>  		writel(cmd, nfc->reg_base + NFC_REG_CMD);
>  
> @@ -520,8 +522,10 @@ static void meson_nfc_dma_buffer_release(struct nand_chip *nand,
>  	struct meson_nfc *nfc = nand_get_controller_data(nand);
>  
>  	dma_unmap_single(nfc->dev, nfc->daddr, datalen, dir);
> -	if (infolen)
> +	if (infolen) {
>  		dma_unmap_single(nfc->dev, nfc->iaddr, infolen, dir);
> +		nfc->info_bytes = 0;
> +	}
>  }
>  
>  static int meson_nfc_read_buf(struct nand_chip *nand, u8 *buf, int len)
> @@ -710,6 +714,8 @@ static void meson_nfc_check_ecc_pages_valid(struct meson_nfc *nfc,
>  		usleep_range(10, 15);
>  		/* info is updated by nfc dma engine*/
>  		smp_rmb();
> +		dma_sync_single_for_cpu(nfc->dev, nfc->iaddr, nfc->info_bytes,
> +					DMA_FROM_DEVICE);
>  		ret = *info & ECC_COMPLETE;
>  	} while (!ret);
>  }