This patch replaces the hardcoded scan delay with a calculated delay that
adjusts to clock rates. This delay is calculated on the basis of a worst case
bus transaction time, with generous built-in margins of error.
Signed-off-by: Cyril Chemparathy <cy...@ti.com>
Signed-off-by: Michael Williamson <michael.william...@criticallink.com>
Signed-off-by: Caglar Akyuz <caglarak...@gmail.com>
---
drivers/net/davinci_mdio.c | 33 +++++++++++++++++++++++----------
1 files changed, 23 insertions(+), 10 deletions(-)
diff --git a/drivers/net/davinci_mdio.c b/drivers/net/davinci_mdio.c
index a9fbc26..f2d7639 100644
--- a/drivers/net/davinci_mdio.c
+++ b/drivers/net/davinci_mdio.c
@@ -83,11 +83,12 @@ struct davinci_mdio_data {
struct device *dev;
struct mii_bus *bus;
bool suspended;
+ unsigned long access_time; /* jiffies */
};
static void __davinci_mdio_reset(struct davinci_mdio_data *data)
{
- u32 mdio_in, div;
+ u32 mdio_in, div, mdio_out_khz, access_time;
mdio_in = clk_get_rate(data->clk);
div = (mdio_in / data->pdata.bus_freq) - 1;
@@ -96,6 +97,25 @@ static void __davinci_mdio_reset(struct davinci_mdio_data
*data)
/* set enable and clock divider */
__raw_writel(div | CONTROL_ENABLE, &data->regs->control);
+
+ /*
+ * One mdio transaction consists of:
+ * 32 bits of preamble
+ * 32 bits of transferred data
+ * 24 bits of bus yield (not needed unless shared?)
+ */
+ mdio_out_khz = mdio_in / (1000 * (div + 1));
+ access_time = (88 * 1000) / mdio_out_khz;
+
+ /*
+ * In the worst case, we could be kicking off a user-access immediately
+ * after the mdio bus scan state-machine triggered its own read. If
+ * so, our request could get deferred by one access cycle. We
+ * defensively allow for 4 access cycles.
+ */
+ data->access_time = usecs_to_jiffies(access_time * 4);
+ if (!data->access_time)
+ data->access_time = 1;
}
static int davinci_mdio_reset(struct mii_bus *bus)
@@ -105,15 +125,8 @@ static int davinci_mdio_reset(struct mii_bus *bus)
__davinci_mdio_reset(data);
- /*
- * wait for scan logic to settle:
- * the scan time consists of (a) a large fixed component, and (b) a
- * small component that varies with the mii bus frequency. These
- * were estimated using measurements at 1.1 and 2.2 MHz on tnetv107x
- * silicon. Since the effect of (b) was found to be largely
- * negligible, we keep things simple here.
- */
- mdelay(1);
+ /* wait for scan logic to settle */
+ msleep(PHY_MAX_ADDR * data->access_time);
/* dump hardware version info */
ver = __raw_readl(&data->regs->version);
--
1.7.0.4
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