From 7c8fef85c070ad582d16d5782e7421700b714918 Mon Sep 17 00:00:00 2001
From: Josh Blum <josh@joshknows.com>
Date: Tue, 3 Jul 2012 17:40:52 -0700
Subject: usrp: cache writes to gpio pins (avoids overhead)

---
 host/lib/usrp/cores/gpio_core_200.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'host')

diff --git a/host/lib/usrp/cores/gpio_core_200.cpp b/host/lib/usrp/cores/gpio_core_200.cpp
index d756097ff..cdab70b8d 100644
--- a/host/lib/usrp/cores/gpio_core_200.cpp
+++ b/host/lib/usrp/cores/gpio_core_200.cpp
@@ -63,6 +63,7 @@ private:
     wb_iface::sptr _iface;
     const size_t _base;
     const size_t _rb_addr;
+    uhd::dict<size_t, boost::uint32_t> _update_cache;
 
     uhd::dict<unit_t, boost::uint16_t> _pin_ctrl, _gpio_out, _gpio_ddr;
     uhd::dict<unit_t, uhd::dict<atr_reg_t, boost::uint16_t> > _atr_regs;
@@ -90,7 +91,12 @@ private:
         const boost::uint32_t ctrl =
             (boost::uint32_t(_pin_ctrl[dboard_iface::UNIT_RX]) << unit2shit(dboard_iface::UNIT_RX)) |
             (boost::uint32_t(_pin_ctrl[dboard_iface::UNIT_TX]) << unit2shit(dboard_iface::UNIT_TX));
-        _iface->poke32(addr, (ctrl & atr_val) | ((~ctrl) & gpio_val));
+        const boost::uint32_t val = (ctrl & atr_val) | ((~ctrl) & gpio_val);
+        if (not _update_cache.has_key(addr) or _update_cache[addr] != val)
+        {
+            _iface->poke32(addr, val);
+        }
+        _update_cache[addr] = val;
     }
 
 };
-- 
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