[PATCH] ADS5121 Fix: put dummy byte to enable fixing EOF bug to first place in order not to break some drivers\nUse ALARM interrupt to avoid waiting for data to come in

 From d500e922b750a2bea554d32d8f12937f4da9c80a Mon Sep 17 00:00:00 2001
From: Matteo Fortini <redacted>
Date: Wed, 10 Dec 2008 19:33:16 +0100
Subject: [PATCH] Fix: put dummy byte to enable fixing EOF bug to first 
place in order not to break some drivers
 Use ALARM interrupt to avoid waiting for data to come in


Signed-off-by: Matteo Fortini <redacted>
---
 drivers/spi/mpc512x_psc_spi.c |   53 
++++++++++++++++++++++++-----------------
 1 files changed, 31 insertions(+), 22 deletions(-)

diff --git a/drivers/spi/mpc512x_psc_spi.c b/drivers/spi/mpc512x_psc_spi.c
index 1fd7ad4..41faa49 100644
--- a/drivers/spi/mpc512x_psc_spi.c
+++ b/drivers/spi/mpc512x_psc_spi.c

@@ -136,6 +136,7 @@ static void mpc512x_psc_spi_deactivate_cs(struct 

spi_device *spi)
                    (spi->mode & SPI_CS_HIGH) ? 1 : 0);
 }
 
+
 /*
  * Current MPC5121's have a bug in the SS logic that requires setting
  * the EOF flag on the next to last byte instead of the last

@@ -155,7 +156,7 @@ static int mpc512x_psc_spi_transfer_rxtx(struct 

spi_device *spi,
 
     if (!tx_buf && !rx_buf && t->len)
         return -EINVAL;
-
+    
     /*
      * zero out Mode register 2
      * From the ref man:

@@ -175,6 +176,7 @@ static int mpc512x_psc_spi_transfer_rxtx(struct 

spi_device *spi,
         u8 data;
         size_t fifosz;
         int rxcount;
+        int txcount;
 
         /*
          * The number of bytes that can be sent at a time

@@ -183,41 +185,49 @@ static int mpc512x_psc_spi_transfer_rxtx(struct 

spi_device *spi,
         fifosz = MPC512x_PSC_FIFO_SZ(in_be32(&fifo->txsz));
         count = min(fifosz, len);
 
+        txcount = 0;
+        /*
+         * Insert a dummy byte before a message of len 1 to make it at 
least 2 bytes long
+         * to be able to set EOF correctly
+         */
+        if (t->len == 1) {
+            out_8(&fifo->txdata_8, 0);
+            txcount++;
+        }
         for (i = count; i > 0; i--) {
             if (len == EOFBYTE || t->len == 1)
                 setbits32(&fifo->txcmd, MPC512x_PSC_FIFO_EOF);
             data = tx_buf ? *tx_buf++ : 0;
             out_8(&fifo->txdata_8, data);
-            if (t->len == 1)
-                out_8(&fifo->txdata_8, 0);
+            txcount++;
             len--;
         }
 
         INIT_COMPLETION(mps->done);
 
-        /* interrupt on tx fifo empty */
-        out_be32(&fifo->txisr, MPC512x_PSC_FIFO_EMPTY);
-        out_be32(&fifo->tximr, MPC512x_PSC_FIFO_EMPTY);
+        /* Enable FIFO_ALARM interrupts for rx_fifo */
+        out_be32(&fifo->rxalarm, txcount);
+        out_be32(&fifo->rxisr, MPC512x_PSC_FIFO_ALARM);
+        out_be32(&fifo->rximr, MPC512x_PSC_FIFO_ALARM);
 
-        /* enable transmiter/receiver */
-        out_8(&psc->command, MPC52xx_PSC_TX_ENABLE | 
MPC52xx_PSC_RX_ENABLE);
-
-        wait_for_completion(&mps->done);
+        /* Disable tx_fifo interrupts */
+        out_be32(&fifo->txisr, 0xffffffff);
+        out_be32(&fifo->tximr, 0);
 
-        mdelay(1);
+        out_8(&psc->command, MPC52xx_PSC_TX_ENABLE | 
MPC52xx_PSC_RX_ENABLE);
 
-        /* rx fifo should have count bytes in it */
-        rxcount = in_be32(&fifo->rxcnt);
-        if (rxcount != count)
-            mdelay(1);
+        wait_for_completion (&mps->done);
 
         rxcount = in_be32(&fifo->rxcnt);
-        if (rxcount != count && t->len != 1)
+        if (rxcount != txcount)
             printk(KERN_WARNING "expected %d bytes in rx fifo "
-                       "but got %d\n", count, rxcount);
-
+                    "but got %d\n", txcount, rxcount);
         rxcount = min(rxcount, count);
         {
+            /* Throw away possible initial dummy byte */
+            if (t->len == 1) {
+                (void)in_8(&fifo->rxdata_8);
+            }
             for (i = rxcount; i > 0; i--) {
                 data = in_8(&fifo->rxdata_8);
                 if (rx_buf)

@@ -418,10 +428,9 @@ static irqreturn_t mpc512x_psc_spi_isr(int irq, 

void *dev_id)
     struct mpc512x_psc_fifo __iomem *fifo = mps->fifo;
 
     /* clear interrupt and wake up the work queue */
-    if (in_be32(&fifo->txisr)
-        & in_be32(&fifo->tximr) & MPC512x_PSC_FIFO_EMPTY) {
-        out_be32(&fifo->txisr, MPC512x_PSC_FIFO_EMPTY);
-        out_be32(&fifo->tximr, 0);
+    if (in_be32(&fifo->rxisr) & in_be32(&fifo->rximr) & 
MPC512x_PSC_FIFO_ALARM) {
+        out_be32(&fifo->rxisr, MPC512x_PSC_FIFO_ALARM);
+        out_be32(&fifo->rximr, 0);
         complete(&mps->done);
         return IRQ_HANDLED;
     }
-- 
1.5.4.3