Re: [PATCH V6, 1/1] mtd: nand: brcmnand: Check flash #WP pin status before nand erase/program

[Boris Brezillon <boris.brezillon@free-electrons.com>]

On Fri, 10 Mar 2017 14:22:39 +0100
Marek Vasut <marek.vasut@gmail.com> wrote:

> On 03/03/2017 10:16 PM, Kamal Dasu wrote:
> > On brcmnand controller v6.x and v7.x, the #WP pin is controlled through
> > the NAND_WP bit in CS_SELECT register.
> > 
> > The driver currently assumes that toggling the #WP pin is
> > instantaneously enabling/disabling write-protection, but it actually
> > takes some time to propagate the new state to the internal NAND chip
> > logic. This behavior is sometime causing data corruptions when an
> > erase/program operation is executed before write-protection has really
> > been disabled.
> > 
> > Fixes: 27c5b17cd1b1 ("mtd: nand: add NAND driver "library" for Broadcom STB NAND controller")
> > Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
> > ---
> >  drivers/mtd/nand/brcmnand/brcmnand.c | 61 ++++++++++++++++++++++++++++++++++--
> >  1 file changed, 58 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
> > index 42ebd73..7419c5c 100644
> > --- a/drivers/mtd/nand/brcmnand/brcmnand.c
> > +++ b/drivers/mtd/nand/brcmnand/brcmnand.c
> > @@ -101,6 +101,9 @@ struct brcm_nand_dma_desc {
> >  #define BRCMNAND_MIN_BLOCKSIZE	(8 * 1024)
> >  #define BRCMNAND_MIN_DEVSIZE	(4ULL * 1024 * 1024)
> >  
> > +#define NAND_CTRL_RDY			(INTFC_CTLR_READY | INTFC_FLASH_READY)
> > +#define NAND_POLL_STATUS_TIMEOUT_MS	100
> > +
> >  /* Controller feature flags */
> >  enum {
> >  	BRCMNAND_HAS_1K_SECTORS			= BIT(0),
> > @@ -765,6 +768,31 @@ enum {
> >  	CS_SELECT_AUTO_DEVICE_ID_CFG		= BIT(30),
> >  };
> >  
> > +static int bcmnand_ctrl_poll_status(struct brcmnand_controller *ctrl,
> > +				    u32 mask, u32 expected_val,
> > +				    unsigned long timeout_ms)
> > +{
> > +	unsigned long limit;
> > +	u32 val;
> > +
> > +	if (!timeout_ms)
> > +		timeout_ms = NAND_POLL_STATUS_TIMEOUT_MS;
> > +
> > +	limit = jiffies + msecs_to_jiffies(timeout_ms);
> > +	do {
> > +		val = brcmnand_read_reg(ctrl, BRCMNAND_INTFC_STATUS);
> > +		if ((val & mask) == expected_val)
> > +			return 0;
> > +
> > +		cpu_relax();
> > +	} while (time_after(limit, jiffies));
> > +
> > +	dev_warn(ctrl->dev, "timeout on status poll (expected %x got %x)\n",
> > +		 expected_val, val & mask);
> > +
> > +	return -ETIMEDOUT;
> > +}
> > +
> >  static inline void brcmnand_set_wp(struct brcmnand_controller *ctrl, bool en)
> >  {
> >  	u32 val = en ? CS_SELECT_NAND_WP : 0;
> > @@ -1024,12 +1052,39 @@ static void brcmnand_wp(struct mtd_info *mtd, int wp)
> >  
> >  	if ((ctrl->features & BRCMNAND_HAS_WP) && wp_on == 1) {
> >  		static int old_wp = -1;  
> 
> Unrelated to this patch, but this static variable should be moved to
> driver's private data instead.
> 
> > +		int ret;
> >  
> >  		if (old_wp != wp) {
> >  			dev_dbg(ctrl->dev, "WP %s\n", wp ? "on" : "off");
> >  			old_wp = wp;
> >  		}
> > +
> > +		/*
> > +		 * make sure ctrl/flash ready before and after
> > +		 * changing state of #WP pin
> > +		 */  
> 
> Shouldn't the brcmnand_set_wp() do this ?

Hm, AFAIU, brcmnand_set_wp() is only controlling the WP pin from the
controller side, so maybe we should rename the function
brcmnand_ctrl_set_wp() to clarify that.

> 
> > +		ret = bcmnand_ctrl_poll_status(ctrl, NAND_CTRL_RDY |
> > +					       NAND_STATUS_READY,
> > +					       NAND_CTRL_RDY |
> > +					       NAND_STATUS_READY, 0);
> > +		if (ret)
> > +			return;
> > +
> >  		brcmnand_set_wp(ctrl, wp);
> > +		chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);
> > +		/* NAND_STATUS_WP 0x00 = protected, 0x80 = not protected */
> > +		ret = bcmnand_ctrl_poll_status(ctrl,
> > +					       NAND_CTRL_RDY |
> > +					       NAND_STATUS_READY |
> > +					       NAND_STATUS_WP,
> > +					       NAND_CTRL_RDY |
> > +					       NAND_STATUS_READY |
> > +					       (wp ? 0 : NAND_STATUS_WP), 0);
> > +
> > +		if (ret)
> > +			dev_err_ratelimited(&host->pdev->dev,
> > +					    "nand #WP expected %s\n",
> > +					    wp ? "on" : "off");
> >  	}
> >  }
> >  
> > @@ -1157,15 +1212,15 @@ static irqreturn_t brcmnand_dma_irq(int irq, void *data)
> >  static void brcmnand_send_cmd(struct brcmnand_host *host, int cmd)
> >  {
> >  	struct brcmnand_controller *ctrl = host->ctrl;
> > -	u32 intfc;
> > +	int ret;
> >  
> >  	dev_dbg(ctrl->dev, "send native cmd %d addr_lo 0x%x\n", cmd,
> >  		brcmnand_read_reg(ctrl, BRCMNAND_CMD_ADDRESS));
> >  	BUG_ON(ctrl->cmd_pending != 0);
> >  	ctrl->cmd_pending = cmd;
> >  
> > -	intfc = brcmnand_read_reg(ctrl, BRCMNAND_INTFC_STATUS);
> > -	WARN_ON(!(intfc & INTFC_CTLR_READY));
> > +	ret = bcmnand_ctrl_poll_status(ctrl, NAND_CTRL_RDY, NAND_CTRL_RDY, 0);
> > +	WARN_ON(ret);
> >  
> >  	mb(); /* flush previous writes */
> >  	brcmnand_write_reg(ctrl, BRCMNAND_CMD_START,
> >   
> 
>