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

[Neil Armstrong]

On 13/03/2023 12:18, Miquel Raynal wrote:
> Hi Arseniy,
>
> avkrasnov@xxxxxxxxxxxxxx wrote on Mon, 13 Mar 2023 10:36:11 +0300:
>
> > 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()'.
>
> The fix looks really legitimate, indeed I get that the usleep_range()
> might make it work most of the time but not always. Having this bit in
> a DMA buf area is a bit strange. Well, the fix LGTM anyway.

Yep it looks legitimate!

LGTM


Reviewed-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>

> > 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);
> > >   }
>
>
> Thanks,
> Miquèl