Re: [PATCH 3/5] mtd: brcmnand: Optional DT flag to reset IPROC NAND controller

[Brian Norris <computersforpeace@gmail.com>]

+ Rafal (to extend this mighty CC list)

On Fri, Oct 02, 2015 at 11:26:44PM +0530, Anup Patel wrote:
> The BRCM NAND controller on NS2 SoC requires a reset to
> cleanup previously configured NAND controller state.
> 
> This patch adds optional boolean device tree flag named
> "brcm,nand-iproc-reset". If this flag is present in NAND
> controller DT node then BRCM IPROC NAND driver will reset
> the NAND controller before any commands are issued.

Is there a reason not to do this reset unconditionally? I recall this
came up in discussion previously, when the OpenWRT folks were trying to
integrate with BCMA, where this reset was one of the few differences
between the platform-device-based driver (i.e., this one) and the BCMA
based driver. Might it help simplify things a bit if we just did the
same thing everywhere?

Brian

> Signed-off-by: Anup Patel <anup.patel@broadcom.com>
> Reviewed-by: Pramod KUMAR <pramodku@broadcom.com>
> Reviewed-by: Ray Jui <rjui@broadcom.com>
> Reviewed-by: Scott Branden <sbranden@broadcom.com>
> ---
>  drivers/mtd/nand/brcmnand/iproc_nand.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/mtd/nand/brcmnand/iproc_nand.c b/drivers/mtd/nand/brcmnand/iproc_nand.c
> index 683495c..d837207 100644
> --- a/drivers/mtd/nand/brcmnand/iproc_nand.c
> +++ b/drivers/mtd/nand/brcmnand/iproc_nand.c
> @@ -11,6 +11,7 @@
>   * GNU General Public License for more details.
>   */
>  
> +#include <linux/delay.h>
>  #include <linux/device.h>
>  #include <linux/io.h>
>  #include <linux/ioport.h>
> @@ -35,6 +36,10 @@ struct iproc_nand_soc_priv {
>  #define IPROC_NAND_APB_LE_MODE             BIT(24)
>  #define IPROC_NAND_INT_CTRL_READ_ENABLE    BIT(6)
>  
> +#define IPROC_NAND_RESET_OFFSET            0x3f8
> +#define IPROC_NAND_RESET_BIT_SHIFT         0
> +#define IPROC_NAND_RESET_BIT               BIT(IPROC_NAND_RESET_BIT_SHIFT)
> +
>  static bool iproc_nand_intc_ack(struct brcmnand_soc *soc)
>  {
>  	struct iproc_nand_soc_priv *priv = soc->priv;
> @@ -93,6 +98,7 @@ static void iproc_nand_apb_access(struct brcmnand_soc *soc, bool prepare)
>  
>  static int iproc_nand_probe(struct platform_device *pdev)
>  {
> +	u32 reset;
>  	struct device *dev = &pdev->dev;
>  	struct iproc_nand_soc_priv *priv;
>  	struct brcmnand_soc *soc;
> @@ -124,6 +130,19 @@ static int iproc_nand_probe(struct platform_device *pdev)
>  	soc->ctlrdy_set_enabled = iproc_nand_intc_set;
>  	soc->prepare_data_bus = iproc_nand_apb_access;
>  
> +	if (of_property_read_bool(dev->of_node, "brcm,nand-iproc-reset")) {
> +		/* Put controller in reset and wait 10 usecs */
> +		reset = readl(priv->idm_base + IPROC_NAND_RESET_OFFSET);
> +		reset |= IPROC_NAND_RESET_BIT;
> +		writel(reset, priv->idm_base + IPROC_NAND_RESET_OFFSET);
> +		udelay(10);
> +		/* Bring controller out of reset and wait 10 usecs */
> +		reset = readl(priv->idm_base + IPROC_NAND_RESET_OFFSET);
> +		reset &= ~IPROC_NAND_RESET_BIT;
> +		writel(reset, priv->idm_base + IPROC_NAND_RESET_OFFSET);
> +		udelay(10);
> +	}
> +
>  	return brcmnand_probe(pdev, soc);
>  }
>  
> -- 
> 1.9.1
>