From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Richard Weinberger <richard@nod.at>,
David Woodhouse <dwmw2@infradead.org>,
Brian Norris <computersforpeace@gmail.com>,
Marek Vasut <marek.vasut@gmail.com>,
Cyrille Pitchen <cyrille.pitchen@atmel.com>,
linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mtd: nand: gpio: make nCE GPIO optional
Date: Mon, 13 Feb 2017 11:30:24 +0100 [thread overview]
Message-ID: <20170213113024.6033990a@bbrezillon> (raw)
In-Reply-To: <20170210140110.87903682E7@localhost.localdomain>
On Fri, 10 Feb 2017 15:01:10 +0100 (CET)
Christophe Leroy <christophe.leroy@c-s.fr> wrote:
> On some hardware, the nCE signal is wired to the ChipSelect associated
> to bus address of the NAND, so it is automatically driven during the
> memory access and it is not managed by a GPIO.
Hm, I'm not sure how this can work, because, AFAIR, the nCE line needs
to stay low for the whole CMD+ADDR[+CMD] cycle, and with your patch
it's not guaranteed.
Can you tell us more about your NAND controller?
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
> drivers/mtd/nand/gpio.c | 18 ++++++++++++------
> 1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mtd/nand/gpio.c b/drivers/mtd/nand/gpio.c
> index 0d24857..85294f1 100644
> --- a/drivers/mtd/nand/gpio.c
> +++ b/drivers/mtd/nand/gpio.c
> @@ -78,7 +78,9 @@ static void gpio_nand_cmd_ctrl(struct mtd_info *mtd, int cmd, unsigned int ctrl)
> gpio_nand_dosync(gpiomtd);
>
> if (ctrl & NAND_CTRL_CHANGE) {
> - gpio_set_value(gpiomtd->plat.gpio_nce, !(ctrl & NAND_NCE));
> + if (gpio_is_valid(gpiomtd->plat.gpio_nce))
> + gpio_set_value(gpiomtd->plat.gpio_nce,
> + !(ctrl & NAND_NCE));
> gpio_set_value(gpiomtd->plat.gpio_cle, !!(ctrl & NAND_CLE));
> gpio_set_value(gpiomtd->plat.gpio_ale, !!(ctrl & NAND_ALE));
> gpio_nand_dosync(gpiomtd);
> @@ -201,7 +203,8 @@ static int gpio_nand_remove(struct platform_device *pdev)
>
> if (gpio_is_valid(gpiomtd->plat.gpio_nwp))
> gpio_set_value(gpiomtd->plat.gpio_nwp, 0);
> - gpio_set_value(gpiomtd->plat.gpio_nce, 1);
> + if (gpio_is_valid(gpiomtd->plat.gpio_nce))
> + gpio_set_value(gpiomtd->plat.gpio_nce, 1);
>
> return 0;
> }
> @@ -239,10 +242,13 @@ static int gpio_nand_probe(struct platform_device *pdev)
> if (ret)
> return ret;
>
> - ret = devm_gpio_request(&pdev->dev, gpiomtd->plat.gpio_nce, "NAND NCE");
> - if (ret)
> - return ret;
> - gpio_direction_output(gpiomtd->plat.gpio_nce, 1);
> + if (gpio_is_valid(gpiomtd->plat.gpio_nce)) {
> + ret = devm_gpio_request(&pdev->dev, gpiomtd->plat.gpio_nce,
> + "NAND NCE");
> + if (ret)
> + return ret;
> + gpio_direction_output(gpiomtd->plat.gpio_nce, 1);
> + }
>
> if (gpio_is_valid(gpiomtd->plat.gpio_nwp)) {
> ret = devm_gpio_request(&pdev->dev, gpiomtd->plat.gpio_nwp,
next prev parent reply other threads:[~2017-02-13 10:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-10 14:01 [PATCH] mtd: nand: gpio: make nCE GPIO optional Christophe Leroy
2017-02-10 15:12 ` Marek Vasut
2017-02-13 10:30 ` Boris Brezillon [this message]
2017-02-13 12:58 ` Christophe LEROY
2017-02-13 13:22 ` Boris Brezillon
2017-03-16 9:35 ` Boris Brezillon
2017-05-01 21:46 ` Brian Norris
2017-05-02 5:47 ` Christophe LEROY
2017-05-02 9:03 ` Boris Brezillon
2017-05-02 16:15 ` Brian Norris
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