From aab3b75fc1a7db54dff630b74158a673b88f8fa1 Mon Sep 17 00:00:00 2001
From: gdisirio <gdisirio@35acf78f-673a-0410-8e92-d51de3d6d3f4>
Date: Sun, 12 Feb 2012 09:30:37 +0000
Subject: Fixed bug 3486930.

git-svn-id: svn://svn.code.sf.net/p/chibios/svn/trunk@3952 35acf78f-673a-0410-8e92-d51de3d6d3f4
---
 os/hal/src/mmc_spi.c | 49 ++-----------------------------------------------
 readme.txt           |  3 +++
 2 files changed, 5 insertions(+), 47 deletions(-)

diff --git a/os/hal/src/mmc_spi.c b/os/hal/src/mmc_spi.c
index f4bcb51fd..06f2594bf 100644
--- a/os/hal/src/mmc_spi.c
+++ b/os/hal/src/mmc_spi.c
@@ -48,53 +48,10 @@
 /* Driver local variables.                                                   */
 /*===========================================================================*/
 
-/**
- * @brief   Lookup table for CRC-7 ( based on polynomial x^7 + x^3 + 1).
- */
-static const uint8_t crc7_lookup_table[256] = {
-  0x00, 0x09, 0x12, 0x1b, 0x24, 0x2d, 0x36, 0x3f, 0x48, 0x41, 0x5a, 0x53,
-  0x6c, 0x65, 0x7e, 0x77, 0x19, 0x10, 0x0b, 0x02, 0x3d, 0x34, 0x2f, 0x26,
-  0x51, 0x58, 0x43, 0x4a, 0x75, 0x7c, 0x67, 0x6e, 0x32, 0x3b, 0x20, 0x29,
-  0x16, 0x1f, 0x04, 0x0d, 0x7a, 0x73, 0x68, 0x61, 0x5e, 0x57, 0x4c, 0x45,
-  0x2b, 0x22, 0x39, 0x30, 0x0f, 0x06, 0x1d, 0x14, 0x63, 0x6a, 0x71, 0x78,
-  0x47, 0x4e, 0x55, 0x5c, 0x64, 0x6d, 0x76, 0x7f, 0x40, 0x49, 0x52, 0x5b,
-  0x2c, 0x25, 0x3e, 0x37, 0x08, 0x01, 0x1a, 0x13, 0x7d, 0x74, 0x6f, 0x66,
-  0x59, 0x50, 0x4b, 0x42, 0x35, 0x3c, 0x27, 0x2e, 0x11, 0x18, 0x03, 0x0a,
-  0x56, 0x5f, 0x44, 0x4d, 0x72, 0x7b, 0x60, 0x69, 0x1e, 0x17, 0x0c, 0x05,
-  0x3a, 0x33, 0x28, 0x21, 0x4f, 0x46, 0x5d, 0x54, 0x6b, 0x62, 0x79, 0x70,
-  0x07, 0x0e, 0x15, 0x1c, 0x23, 0x2a, 0x31, 0x38, 0x41, 0x48, 0x53, 0x5a,
-  0x65, 0x6c, 0x77, 0x7e, 0x09, 0x00, 0x1b, 0x12, 0x2d, 0x24, 0x3f, 0x36,
-  0x58, 0x51, 0x4a, 0x43, 0x7c, 0x75, 0x6e, 0x67, 0x10, 0x19, 0x02, 0x0b,
-  0x34, 0x3d, 0x26, 0x2f, 0x73, 0x7a, 0x61, 0x68, 0x57, 0x5e, 0x45, 0x4c,
-  0x3b, 0x32, 0x29, 0x20, 0x1f, 0x16, 0x0d, 0x04, 0x6a, 0x63, 0x78, 0x71,
-  0x4e, 0x47, 0x5c, 0x55, 0x22, 0x2b, 0x30, 0x39, 0x06, 0x0f, 0x14, 0x1d,
-  0x25, 0x2c, 0x37, 0x3e, 0x01, 0x08, 0x13, 0x1a, 0x6d, 0x64, 0x7f, 0x76,
-  0x49, 0x40, 0x5b, 0x52, 0x3c, 0x35, 0x2e, 0x27, 0x18, 0x11, 0x0a, 0x03,
-  0x74, 0x7d, 0x66, 0x6f, 0x50, 0x59, 0x42, 0x4b, 0x17, 0x1e, 0x05, 0x0c,
-  0x33, 0x3a, 0x21, 0x28, 0x5f, 0x56, 0x4d, 0x44, 0x7b, 0x72, 0x69, 0x60,
-  0x0e, 0x07, 0x1c, 0x15, 0x2a, 0x23, 0x38, 0x31, 0x46, 0x4f, 0x54, 0x5d,
-  0x62, 0x6b, 0x70, 0x79
-};
-
 /*===========================================================================*/
 /* Driver local functions.                                                   */
 /*===========================================================================*/
 
-/**
- * @brief Calculate the MMC standard CRC-7 based on a lookup table.
- *
- * @param[in] crc       start value for CRC
- * @param[in] buffer    pointer to data buffer
- * @param[in] len       length of data
- * @return              Calculated CRC
- */
-static uint8_t crc7(uint8_t crc, const uint8_t *buffer, size_t len) {
-
-  while (len--)
-    crc = crc7_lookup_table[(crc << 1) ^ (*buffer++)];
-  return crc;
-}
-
 /**
  * @brief   Inserion monitor timer callback function.
  *
@@ -141,7 +98,7 @@ static void wait(MMCDriver *mmcp) {
   for (i = 0; i < 16; i++) {
     spiReceive(mmcp->spip, 1, buf);
     if (buf[0] == 0xFF)
-      break;
+      return;
   }
   /* Looks like it is a long wait.*/
   while (TRUE) {
@@ -175,9 +132,7 @@ static void send_hdr(MMCDriver *mmcp, uint8_t cmd, uint32_t arg) {
   buf[2] = arg >> 16;
   buf[3] = arg >> 8;
   buf[4] = arg;
-  /* Calculate CRC for command header, shift to right position, add stop bit.*/
-  buf[5] = ((crc7(0, buf, 5) & 0x7F) << 1) | 0x01;
-
+  buf[5] = 0x95;        /* Valid for CMD0 ignored by other commands. */
   spiSend(mmcp->spip, 6, buf);
 }
 
diff --git a/readme.txt b/readme.txt
index ccaa7d81f..cbdf1be41 100644
--- a/readme.txt
+++ b/readme.txt
@@ -79,6 +79,9 @@
 *****************************************************************************
 
 *** 2.5.0 ***
+- FIX: Fixed MMC over SPI driver performs an unnecessary SPI read (bug
+  3486930)(backported to 2.2.9 and 2.4.1). Also removed unnecessary CRC7
+  calculation.
 - FIX: Fixed Realtime counter initialization in STM32 HALs (bug 3485500)
   (backported to 2.4.1).
 - FIX: Fixed PPC port broken when CH_DBG_SYSTEM_STATE_CHECK is activated
-- 
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