Re: [PATCH v7 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller

From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Liang Yang <liang.yang@amlogic.com>
Cc: Rob Herring <robh@kernel.org>,
	Hanjie Lin <hanjie.lin@amlogic.com>,
	Victor Wan <victor.wan@amlogic.com>,
	Jianxin Pan <jianxin.pan@amlogic.com>,
	Neil Armstrong <narmstrong@baylibre.com>,
	Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
	Richard Weinberger <richard@nod.at>,
	Yixun Lan <yixun.lan@amlogic.com>,
	linux-kernel@vger.kernel.org, Marek Vasut <marek.vasut@gmail.com>,
	Jian Hu <jian.hu@amlogic.com>,
	linux-mtd@lists.infradead.org,
	Kevin Hilman <khilman@baylibre.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>,
	Carlo Caione <carlo@caione.org>,
	linux-amlogic@lists.infradead.org,
	Brian Norris <computersforpeace@gmail.com>,
	David Woodhouse <dwmw2@infradead.org>,
	linux-arm-kernel@lists.infradead.org,
	Jerome Brunet <jbrunet@baylibre.com>
Subject: Re: [PATCH v7 2/2] mtd: rawnand: meson: add support for Amlogic NAND flash controller
Date: Mon, 10 Dec 2018 12:38:09 +0100	[thread overview]
Message-ID: <20181210123809.5ade45c4@bbrezillon> (raw)
In-Reply-To: <823825a3-86fb-9a20-ae29-85cc52d44093@amlogic.com>

On Mon, 10 Dec 2018 19:23:46 +0800
Liang Yang <liang.yang@amlogic.com> wrote:

> >> +			mtd->ecc_stats.failed++;
> >> +			continue;
> >> +		}
> >> +		mtd->ecc_stats.corrected += ECC_ERR_CNT(*info);
> >> +		bitflips = max_t(u32, bitflips, ECC_ERR_CNT(*info));
> >> +	}  
> > 
> > Are you sure you handle correctly empty pages with bf?
> >   
> if scramble is enable, i would say yes here.
> when scramble is disabled, i am considering how to use the helper 
> nand_check_erased_ecc_chunk, but it seems that i can't get the ecc
> bytes which is caculated by ecc engine.by the way, nfc dma doesn't send 
> out the ecc parity bytes.

Even if the ECC engine is disabled?

> so i would suggest using scramble.
> 

No, please don't force people to use the scrambler.

> >> +
> >> +const void *
> >> +meson_nand_op_get_dma_safe_output_buf(const struct nand_op_instr *instr)
> >> +{
> >> +	if (WARN_ON(instr->type != NAND_OP_DATA_OUT_INSTR))
> >> +		return NULL;
> >> +
> >> +	if (virt_addr_valid(instr->ctx.data.buf.out) &&
> >> +	    !object_is_on_stack(instr->ctx.data.buf.out))  
> > 
> > Can you please create helpers for that? I guess it will help removing
> > these checks once the core will have a DMA-safe approach.
> >   
> I will use below definition:
> #define BUFFER_IS_DMA_SAFE(x)	\
> 	(virt_addr_valid((x)) && (!object_is_on_stack((x))))
> 
> Is it ok?

Please define a function, not a macro.

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