From 292e7cab73c75260b7cfb7f90ad28938c8f1117a Mon Sep 17 00:00:00 2001
From: Michael Sevakis <jethead71@rockbox.org>
Date: Sun, 18 Dec 2011 10:41:43 +0000
Subject: Gigabeat S: PMIC SPI improvement and bugfixes.

Nick some aspects from the as3525 ascodec driver to improve throughput in
the beast's SPI communications by switching tranfer descriptors to the
caller's stack and getting rid of thread synchronization.

Fix a bug that suddenly became obvious that could permanently stall the SPI
driver because all data could be shifted out before the interrupt could get
serviced. In that case, it needs a kick to restart it. Should probably put
the SPI interrupt priority above DVFS.

A tweak to the event registration interface to simplify it.


git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31353 a1c6a512-1295-4272-9138-f99709370657
---
 firmware/target/arm/imx31/spi-imx31.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

(limited to 'firmware/target/arm/imx31/spi-imx31.c')

diff --git a/firmware/target/arm/imx31/spi-imx31.c b/firmware/target/arm/imx31/spi-imx31.c
index 7fcf94ce90..ea3d2f8d77 100644
--- a/firmware/target/arm/imx31/spi-imx31.c
+++ b/firmware/target/arm/imx31/spi-imx31.c
@@ -170,7 +170,10 @@ static bool start_transfer(struct spi_module_desc * const desc,
     unsigned long intreg;
 
     if (!spi_set_context(desc, xfer))
+    {
+        xfer->count = -1;
         return false;
+    }
 
     base[CONREG] |= CSPI_CONREG_EN; /* Enable module */
 
@@ -249,8 +252,18 @@ static void spi_interrupt(enum spi_module_number spi)
     if (xfer->count > 0)
     {
         /* Data to transmit - fill TXFIFO or write until exhausted. */
-        if (tx_fill_fifo(desc, base, xfer) != 0)
-            return;
+        int remaining = tx_fill_fifo(desc, base, xfer);
+
+        /* If transfer completed because TXFIFO ran out of data, resume it or
+           else it will not finish. */
+        if (!(base[CONREG] & CSPI_CONREG_XCH))
+        {
+            base[STATREG] = CSPI_STATREG_TC;
+            base[CONREG] |= CSPI_CONREG_XCH;
+        }
+
+        if (remaining > 0)
+            return; /* Still more after this */
 
         /* Out of data - stop TX interrupts, enable TC interrupt. */
         intreg &= ~CSPI_INTREG_THEN;
@@ -263,7 +276,6 @@ static void spi_interrupt(enum spi_module_number spi)
         /* Outbound transfer is complete. */
         intreg &= ~CSPI_INTREG_TCEN;
         base[INTREG] = intreg;
-        base[STATREG] = CSPI_STATREG_TC; /* Ack 'complete' */
     }
 
     if (intreg != 0)
@@ -276,8 +288,6 @@ static void spi_interrupt(enum spi_module_number spi)
         spi_transfer_cb_fn_type callback = xfer->callback;
         xfer->next = NULL;
 
-        base[CONREG] &= ~CSPI_CONREG_EN; /* Disable module */
-
         if (next == xfer)
         {
             /* Last job on queue */
@@ -287,6 +297,8 @@ static void spi_interrupt(enum spi_module_number spi)
                 callback(xfer);
 
             /* Callback may have restarted transfers. */
+            if (desc->head == NULL)
+                base[CONREG] &= ~CSPI_CONREG_EN; /* Disable module */
         }
         else
         {
@@ -299,7 +311,6 @@ static void spi_interrupt(enum spi_module_number spi)
             if (!start_transfer(desc, next))
             {
                 xfer = next;
-                xfer->count = -1;
                 continue; /* Failed: try next */
             }
         }
@@ -416,10 +427,6 @@ bool spi_transfer(struct spi_transfer_desc *xfer)
             desc->tail = xfer;
             xfer->next = xfer; /* First, self-reference terminate */
         }
-        else
-        {
-            xfer->count = -1; /* Signal error */
-        }
     }
     else
     {
-- 
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