Messages in this thread Patch in this message | | | Date | Mon, 27 Sep 2021 18:31:50 +0200 | From | Miquel Raynal <> | Subject | Re: [PATCH v2] mtd: rawnand: xway: No hardcoded ECC engine, use device tree setting |
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Hi Jan,
Sorry for the delay, I had to rethink about the problem first.
jan@3e8.eu wrote on Sat, 18 Sep 2021 23:26:48 +0200:
> Hi Miquèl, > > > Yes this was my understanding, that only software ECC engine was > > supported. The mainline driver shows absolutely no signs of hardware > > ECC engine support. > > > > Perhaps however you mean that on-die ECC engine are not supported > > anymore because of the engine_type being set in attach_chip()? > > Yes, this is exactly the issue. > > > If yes then indeed there is something to do, perhaps checking if an > > engine has been already set is enough? You can try something like: > > > > if (engine_type == unknown) > > engine_type = soft; > > Checking for NAND_ECC_ENGINE_TYPE_INVALID doesn't work, as the engine > type is already set to NAND_ECC_ENGINE_TYPE_ON_HOST by rawnand_dt_init. > The code there seems to expect that chip->ecc.engine_type contains the > default value, which is no longer the case after commit 525914b5bd8 > ("mtd: rawnand: xway: Move the ECC initialization to ->attach_chip()").
This is indeed an issue and should be fixed. However the solution is I think already available in the raw NAND core (but I had to dig into the code again to remember how I wanted to handle this).
> The following in attach_chip works: > > if (chip->ecc.engine_type == NAND_ECC_ENGINE_TYPE_ON_HOST) > chip->ecc.engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
If you look at the rawnand_dt_init() function [1] the logic is:
Is the user configuration (DT) valid ? if yes take it. Is the NAND controller driver setting a default mode? if yes take it. Otherwise take the raw NAND subsystem default: ON_HOST.
This logic happens very soon in the init process so the default mode for the driver should be provided before the nand_scan() call.
So what I propose is: - in the driver probe: set the default to software ECC - in the attach() hook: drop the line setting the engine_type to SOFT.
Please check the below diff and tell me if it works for you. I'll then propose a wider series fixing the other drivers as well.
> However, this will also silently use the software ECC engine if anyone > actually configures the on-host hardware ECC engine in the device tree > (which is of course unsupported for xway). > > Thanks, > Jan
[1] https://elixir.bootlin.com/linux/latest/source/drivers/mtd/nand/raw/nand_base.c#L5328
Thanks, Miquèl
--- diff --git a/drivers/mtd/nand/raw/xway_nand.c b/drivers/mtd/nand/raw/xway_nand.c index 26751976e502..d9e167dbb717 100644 --- a/drivers/mtd/nand/raw/xway_nand.c +++ b/drivers/mtd/nand/raw/xway_nand.c @@ -148,9 +148,8 @@ static void xway_write_buf(struct nand_chip *chip, const u_char *buf, int len) static int xway_attach_chip(struct nand_chip *chip) { - chip->ecc.engine_type = NAND_ECC_ENGINE_TYPE_SOFT; - - if (chip->ecc.algo == NAND_ECC_ALGO_UNKNOWN) + if (chip->ecc.engine_type == NAND_ECC_ENGINE_TYPE_SOFT && + chip->ecc.algo == NAND_ECC_ALGO_UNKNOWN) chip->ecc.algo = NAND_ECC_ALGO_HAMMING; return 0; @@ -219,6 +218,14 @@ static int xway_nand_probe(struct platform_device *pdev) | NAND_CON_SE_P | NAND_CON_WP_P | NAND_CON_PRE_P | cs_flag, EBU_NAND_CON); + /* + * This controller has no hardware ECC engine and the driver assumes + * that the default ECC engine should be TYPE_SOFT. Set ->engine_type + * before the NAND registration in order to provide a default value. + */ + data->chip.ecc.engine_type = NAND_ECC_ENGINE_TYPE_SOFT; + + /* Scan to find existence of the device */ err = nand_scan(&data->chip, 1); if (err)
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