Re: [PATCH V5,] mtd: nand: brcmnand: Check flash #WP pin status before nand erase/program

Boris Brezillon
2017-03-01T21:27:41Z

On Wed, 1 Mar 2017 15:38:51 -0500
Kamal Dasu <kdasu.kdev@gmail.com> wrote:

> On Wed, Mar 1, 2017 at 3:01 PM, Boris Brezillon
> <boris.brezillon@free-electrons.com> wrote:
> > On Wed, 1 Mar 2017 14:27:30 -0500
> > Kamal Dasu <kdasu.kdev@gmail.com> wrote:
> >
> >> brcmnand controller v6.x and v7.x lets driver to enable disable #WP pin
> >> via NAND_WP bit in CS_SELECT register. Driver implementation assumes that
> >> setting/resetting the bit would assert/de-assert #WP pin instantaneously
> >> from the flash part's perspective, and was proceeding to erase/program
> >> without verifying flash status byte for protection bit. In rigorous
> >> testing this was causing rare data corruptions with erase and/or
> >> subsequent programming. To fix this check NAND status in addition to
> >> controller #WP pin status. This change makes sure both sides are ready
> >> to accept new commands.
> >
> > You didn't fix the commit message.
> >
>
> I did change the message based on PATCH V3. 2/2 comments.
>
> " ^ To fix this, check the NAND status in
> addition to the NAND controller #WP pin status. This way, we make sure
> both sides are ready to accept new commands."
>
> Am I missing something ?

The first sentence sounds weird to me, but I'm probably not the best
person to judge if the it is correct.

I would rephrase it like that:

"
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.

To prevent such problems, check the NAND status byte each time we toggle
the #WP pin.
"

> >> from the flash part's perspective

> >> via NAND_WP bit in CS_SELECT register. Driver implementation assumes that
> >> setting/resetting the bit would assert/de-assert #WP pin instantaneously
> >> from the flash part's perspective, and was proceeding to erase/program
> >> without verifying flash status byte for protection bit. In rigorous
> >> testing this was causing rare data corruptions with erase and/or
> >> subsequent programming. To fix this check NAND status in addition to
> >> controller #WP pin status. This change makes sure both sides are ready
> >> to accept new commands.

>
> >>
> >> Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
> >> ---
> >
> > Note for future submissions: when you have a single patch, please put
> > a changelog (changes introduced by each new version) here.
> >
>
> So you want me to resend with the change log ?.

Let's wait for other reviews. BTW, don't you want to backport this fix
(Fixes+Cc-stable tags)?

>
> >> 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;
> >> + 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
> >> + */
> >> + 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,
> >
>
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