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

[Neil Armstrong <neil.armstrong@linaro.org>]

On 13/03/2023 12:18, Miquel Raynal wrote:
> Hi Arseniy,
> 
> avkrasnov@sberdevices.ru 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@linaro.org>

> 
>>
>> 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@sberdevices.ru>
>>> ---
>>>   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


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