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author | Rouven Czerwinski <r.czerwinski@pengutronix.de> | 2019-06-11 08:51:21 +0200 |
---|---|---|
committer | Sascha Hauer <s.hauer@pengutronix.de> | 2019-06-11 10:30:12 +0200 |
commit | b7c0ec207ef11ce756e169e8507d97a57305dc87 (patch) | |
tree | cb54044fb9099524073486a7f3c32809ed213862 /drivers/nvmem | |
parent | 18ac9ebab9cb5146ea2b0d93719c89834c95ad55 (diff) | |
download | barebox-b7c0ec207ef11ce756e169e8507d97a57305dc87.tar.gz barebox-b7c0ec207ef11ce756e169e8507d97a57305dc87.tar.xz |
nvmem: ocotp: Change TIMING calculation algorithm
Port of patch from linux-arm-kernel:
| From: Bryan O'Donoghue <pure.logic@nexus-software.ie>
|
| nvmem: imx-ocotp: Change TIMING calculation to u-boot algorithm
|
| The RELAX field of the OCOTP block is turning out as a zero on i.MX8MM.
| This messes up the subsequent re-load of the fuse shadow registers.
|
| After some discussion with people @ NXP its clear we have missed a trick
| here in Linux.
|
| The OCOTP fuse programming time has a physical minimum 'burn time' that is
| not related to the ipg_clk.
|
| We need to define the RELAX, STROBE_READ and STROBE_PROG fields in terms of
| desired timings to allow for the burn-in to safely complete. Right now only
| the RELAX field is calculated in terms of an absolute time and we are
| ending up with a value of zero.
|
| This patch inherits the u-boot timings for the OCOTP_TIMING calculation on
| the i.MX6 and i.MX8. Those timings are known to work and critically specify
| values such as STROBE_PROG as a minimum timing.
Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Diffstat (limited to 'drivers/nvmem')
-rw-r--r-- | drivers/nvmem/ocotp.c | 38 |
1 files changed, 34 insertions, 4 deletions
diff --git a/drivers/nvmem/ocotp.c b/drivers/nvmem/ocotp.c index c21327805b..3f9f162860 100644 --- a/drivers/nvmem/ocotp.c +++ b/drivers/nvmem/ocotp.c @@ -69,7 +69,9 @@ /* Other definitions */ #define IMX6_OTP_DATA_ERROR_VAL 0xBADABADA -#define DEF_RELAX 20 +#define TIMING_STROBE_PROG_US 10 +#define TIMING_STROBE_READ_NS 37 +#define TIMING_RELAX_NS 17 #define MAC_OFFSET_0 (0x22 * 4) #define IMX6UL_MAC_OFFSET_1 (0x23 * 4) #define MAC_OFFSET_1 (0x24 * 4) @@ -119,11 +121,39 @@ static int imx6_ocotp_set_timing(struct ocotp_priv *priv) u32 relax, strobe_read, strobe_prog; u32 timing; + /* + * Note: there are minimum timings required to ensure an OTP fuse burns + * correctly that are independent of the ipg_clk. Those values are not + * formally documented anywhere however, working from the minimum + * timings given in u-boot we can say: + * + * - Minimum STROBE_PROG time is 10 microseconds. Intuitively 10 + * microseconds feels about right as representative of a minimum time + * to physically burn out a fuse. + * + * - Minimum STROBE_READ i.e. the time to wait post OTP fuse burn before + * performing another read is 37 nanoseconds + * + * - Minimum RELAX timing is 17 nanoseconds. This final RELAX minimum + * timing is not entirely clear the documentation says "This + * count value specifies the time to add to all default timing + * parameters other than the Tpgm and Trd. It is given in number + * of ipg_clk periods." where Tpgm and Trd refer to STROBE_PROG + * and STROBE_READ respectively. What the other timing parameters + * are though, is not specified. Experience shows a zero RELAX + * value will mess up a re-load of the shadow registers post OTP + * burn. + */ clk_rate = clk_get_rate(priv->clk); - relax = clk_rate / (1000000000 / DEF_RELAX) - 1; - strobe_prog = clk_rate / (1000000000 / 10000) + 2 * (DEF_RELAX + 1) - 1; - strobe_read = clk_rate / (1000000000 / 40) + 2 * (DEF_RELAX + 1) - 1; + relax = DIV_ROUND_UP(clk_rate * TIMING_RELAX_NS, 1000000000) - 1; + + strobe_read = DIV_ROUND_UP(clk_rate * TIMING_STROBE_READ_NS, + 1000000000); + strobe_read += 2 * (relax + 1) - 1; + strobe_prog = DIV_ROUND_CLOSEST(clk_rate * TIMING_STROBE_PROG_US, + 1000000); + strobe_prog += 2 * (relax + 1) - 1; timing = readl(priv->base + OCOTP_TIMING) & OCOTP_TIMING_WAIT_MASK; timing |= BF(relax, OCOTP_TIMING_RELAX); |