Re: [PATCH 3/3] i2c: mpc: implement erratum A-004447 workaround

[Chris Packham <Chris.Packham@alliedtelesis.co.nz>]

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On 6/05/21 8:03 pm, Andy Shevchenko wrote:


On Thursday, May 6, 2021, Chris Packham <chris.packham@alliedtelesis.co.nz<mailto:chris.packham@alliedtelesis.co.nz>> wrote:
The P2040/P2041 has an erratum where the normal i2c recovery mechanism
does not work. Implement the alternative recovery mechanism documented
in the P2040 Chip Errata Rev Q.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz<mailto:chris.packham@alliedtelesis.co.nz>>
---
 drivers/i2c/busses/i2c-mpc.c | 88 +++++++++++++++++++++++++++++++++++-
 1 file changed, 86 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index 30d9e89a3db2..052e37718771 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -45,6 +45,7 @@
 #define CCR_MTX  0x10
 #define CCR_TXAK 0x08
 #define CCR_RSTA 0x04
+#define CCR_RSVD 0x02

 #define CSR_MCF  0x80
 #define CSR_MAAS 0x40
@@ -97,7 +98,7 @@ struct mpc_i2c {
        u32 block;
        int rc;
        int expect_rxack;
-
+       bool has_errata_A004447;
 };

 struct mpc_i2c_divider {
@@ -136,6 +137,83 @@ static void mpc_i2c_fixup(struct mpc_i2c *i2c)
        }
 }

+static int i2c_mpc_wait_sr(struct mpc_i2c *i2c, int mask)
+{
+       unsigned long timeout = jiffies + usecs_to_jiffies(100);
+       int ret = 0;
+
+       while ((readb(i2c->base + MPC_I2C_SR) & mask) == 0) {
+               if (time_after(jiffies, timeout)) {
+                       ret = -ETIMEDOUT;
+                       break;
+               }
+               cond_resched();
+       }
+
+       return ret;
+}

readb_poll_timeout()


Thanks. I figured this existed I was just grepping for wait_.* and didn't find it. I'll prepare a v2 and get it out by the end of my day.

+
+/*
+ * Workaround for Erratum A004447. From the P2040CE Rev Q
+ *
+ * 1.  Set up the frequency divider and sampling rate.
+ * 2.  I2CCR - a0h
+ * 3.  Poll for I2CSR[MBB] to get set.
+ * 4.  If I2CSR[MAL] is set (an indication that SDA is stuck low), then go to
+ *     step 5. If MAL is not set, then go to step 13.
+ * 5.  I2CCR - 00h
+ * 6.  I2CCR - 22h
+ * 7.  I2CCR - a2h
+ * 8.  Poll for I2CSR[MBB] to get set.
+ * 9.  Issue read to I2CDR.
+ * 10. Poll for I2CSR[MIF] to be set.
+ * 11. I2CCR - 82h
+ * 12. Workaround complete. Skip the next steps.
+ * 13. Issue read to I2CDR.
+ * 14. Poll for I2CSR[MIF] to be set.
+ * 15. I2CCR - 80h
+ */
+static void mpc_i2c_fixup_A004447(struct mpc_i2c *i2c)
+{
+       int ret;
+       u32 val;
+
+       writeccr(i2c, CCR_MEN | CCR_MSTA);
+       ret = i2c_mpc_wait_sr(i2c, CSR_MBB);
+       if (ret) {
+               dev_err(i2c->dev, "timeout waiting for CSR_MBB\n");
+               return;
+       }
+
+       val = readb(i2c->base + MPC_I2C_SR);
+
+       if (val & CSR_MAL) {
+               writeccr(i2c, 0x00);
+               writeccr(i2c, CCR_MSTA | CCR_RSVD);
+               writeccr(i2c, CCR_MEN | CCR_MSTA | CCR_RSVD);
+               ret = i2c_mpc_wait_sr(i2c, CSR_MBB);
+               if (ret) {
+                       dev_err(i2c->dev, "timeout waiting for CSR_MBB\n");
+                       return;
+               }
+               val = readb(i2c->base + MPC_I2C_DR);
+               ret = i2c_mpc_wait_sr(i2c, CSR_MIF);
+               if (ret) {
+                       dev_err(i2c->dev, "timeout waiting for CSR_MIF\n");
+                       return;
+               }
+               writeccr(i2c, CCR_MEN | CCR_RSVD);
+       } else {
+               val = readb(i2c->base + MPC_I2C_DR);
+               ret = i2c_mpc_wait_sr(i2c, CSR_MIF);
+               if (ret) {
+                       dev_err(i2c->dev, "timeout waiting for CSR_MIF\n");
+                       return;
+               }
+               writeccr(i2c, CCR_MEN);
+       }
+}
+
 #if defined(CONFIG_PPC_MPC52xx) || defined(CONFIG_PPC_MPC512x)
 static const struct mpc_i2c_divider mpc_i2c_dividers_52xx[] = {
        {20, 0x20}, {22, 0x21}, {24, 0x22}, {26, 0x23},
@@ -670,7 +748,10 @@ static int fsl_i2c_bus_recovery(struct i2c_adapter *adap)
 {
        struct mpc_i2c *i2c = i2c_get_adapdata(adap);

-       mpc_i2c_fixup(i2c);
+       if (i2c->has_errata_A004447)
+               mpc_i2c_fixup_A004447(i2c);
+       else
+               mpc_i2c_fixup(i2c);

        return 0;
 }
@@ -767,6 +848,9 @@ static int fsl_i2c_probe(struct platform_device *op)
        }
        dev_info(i2c->dev, "timeout %u us\n", mpc_ops.timeout * 1000000 / HZ);

+       if (of_property_read_bool(op->dev.of_node, "fsl,i2c-erratum-a004447"))
+               i2c->has_errata_A004447 = true;
+
        i2c->adap = mpc_ops;
        scnprintf(i2c->adap.name<http://adap.name>, sizeof(i2c->adap.name<http://adap.name>),
                  "MPC adapter (%s)", of_node_full_name(op->dev.of_node));
--
2.31.1



--
With Best Regards,
Andy Shevchenko



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