- udelay(30);
- regmap_read(rk_phy->reg_base,
- rk_phy->reg_offset + GRF_EMMCPHY_STATUS,
- &dllrdy);
- dllrdy = (dllrdy >> PHYCTRL_DLLRDY_SHIFT) & PHYCTRL_DLLRDY_MASK;
+ if (rate == 0)
+ return 0;
+
+ /*
+ * After enabling analog DLL circuits docs say that we need 10.2 us if
+ * our source clock is at 50 MHz and that lock time scales linearly
+ * with clock speed. If we are powering on the PHY and the card clock
+ * is super slow (like 100 kHZ) this could take as long as 5.1 ms as
+ * per the math: 10.2 us * (50000000 Hz / 100000 Hz) => 5.1 ms
+ * Hopefully we won't be running at 100 kHz, but we should still make
+ * sure we wait long enough.
+ *
+ * NOTE: There appear to be corner cases where the DLL seems to take
+ * extra long to lock for reasons that aren't understood. In some
+ * extreme cases we've seen it take up to over 10ms (!). We'll be
+ * generous and give it 50ms. We still busy wait here because:
+ * - In most cases it should be super fast.
+ * - This is not called lots during normal operation so it shouldn't
+ * be a power or performance problem to busy wait. We expect it
+ * only at boot / resume. In both cases, eMMC is probably on the
+ * critical path so busy waiting a little extra time should be OK.
+ */
+ timeout = jiffies + msecs_to_jiffies(50);
+ do {
+ udelay(1);
+
+ regmap_read(rk_phy->reg_base,
+ rk_phy->reg_offset + GRF_EMMCPHY_STATUS,
+ &dllrdy);
+ dllrdy = (dllrdy >> PHYCTRL_DLLRDY_SHIFT) & PHYCTRL_DLLRDY_MASK;
+ if (dllrdy == PHYCTRL_DLLRDY_DONE)
+ break;
+ } while (!time_after(jiffies, timeout));
+