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Date: Tue, 6 Jan 2009 15:17:01 +0100
From: Wolfgang Mües <wolfgang.mues@...rswald.de>
To: "David Brownell" <dbrownell@...rs.sourceforge.net>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] Fixes and enhancements for the MMC SPI driver
David,
I have done some fixes and enhancements to the MMC SPI host controller driver.
Practical results with SD/SDHC cards from different vendors are much better now.
The patch is for kernel 2.6.28.
(I do not read the linux kernel mailing list)
Signed-off-by: Wolfgang Muees <wolfgang.mues@...rswald.de>
============= snip ====================
--- 2.6.28/drivers/mmc/host/mmc_spi.c 2008-11-24 10:26:06.000000000 +0100
+++ new/drivers/mmc/host/mmc_spi.c 2009-01-06 14:52:59.000000000 +0100
@@ -25,6 +25,7 @@
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/hrtimer.h>
+#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/bio.h>
#include <linux/dma-mapping.h>
@@ -186,10 +187,10 @@
static int
mmc_spi_skip(struct mmc_spi_host *host, ktime_t timeout, unsigned n, u8 byte)
{
- u8 *cp = host->data->status;
-
- timeout = ktime_add(timeout, ktime_get());
-
+ u8 *cp = host->data->status;
+ unsigned long timeout_jiffies = (unsigned long) ((ktime_to_us(timeout) * HZ) / 1000000);
+ unsigned long starttime = jiffies;
+
while (1) {
int status;
unsigned i;
@@ -203,11 +204,13 @@
return cp[i];
}
- /* REVISIT investigate msleep() to avoid busy-wait I/O
- * in at least some cases.
- */
- if (ktime_to_ns(ktime_sub(ktime_get(), timeout)) > 0)
+ if ((jiffies - starttime) > timeout_jiffies)
break;
+ /* If we need long timeouts, we may release the CPU. */
+ /* We use jiffies here because we want to have a relation between
+ elapsed time and the blocking of the scheduler. */
+ if ((jiffies - starttime) > 1)
+ schedule();
}
return -ETIMEDOUT;
}
@@ -280,7 +283,9 @@
* It'd probably be better to memcpy() the first chunk and
* avoid extra i/o calls...
*/
- for (i = 2; i < 9; i++) {
+ /* Note we check for more than 8 bytes, because in practice,
+ some SD cards are slow... */
+ for (i = 2; i < 16; i++) {
value = mmc_spi_readbytes(host, 1);
if (value < 0)
goto done;
@@ -609,6 +614,15 @@
struct spi_device *spi = host->spi;
int status, i;
struct scratch *scratch = host->data;
+ u32 pattern;
+
+ /* The MMC framework does a good job of computing timeouts
+ according to the mmc/sd standard. However, we found that in
+ SPI mode, there are many cards which need a longer timeout
+ of 1s after receiving a long stream of write data. */
+ struct timeval tv = ktime_to_timeval(timeout);
+ if (tv.tv_sec == 0)
+ timeout = ktime_set(1,0);
if (host->mmc->use_spi_crc)
scratch->crc_val = cpu_to_be16(
@@ -636,8 +650,23 @@
* doesn't necessarily tell whether the write operation succeeded;
* it just says if the transmission was ok and whether *earlier*
* writes succeeded; see the standard.
- */
- switch (SPI_MMC_RESPONSE_CODE(scratch->status[0])) {
+ *
+ * In practice, there are (even modern SDHC-)Cards which need
+ * some bits to send the response, so we have to cope with this
+ * situation and check the response bit-by-bit. Arggh!!!
+ */
+ pattern = scratch->status[0] << 24;
+ pattern |= scratch->status[1] << 16;
+ pattern |= scratch->status[2] << 8;
+ pattern |= scratch->status[3];
+
+ /* left-adjust to leading 0 bit */
+ while (pattern & 0x80000000)
+ pattern <<= 1;
+ /* right-adjust for pattern matching. Code is in bit 4..0 now. */
+ pattern >>= 27;
+
+ switch (pattern) {
case SPI_RESPONSE_ACCEPTED:
status = 0;
break;
@@ -668,9 +697,9 @@
/* Return when not busy. If we didn't collect that status yet,
* we'll need some more I/O.
*/
- for (i = 1; i < sizeof(scratch->status); i++) {
- if (scratch->status[i] != 0)
- return 0;
+ for (i = 4; i < sizeof(scratch->status); i++) {
+ if (scratch->status[i] & 0x01)
+ return 0;
}
return mmc_spi_wait_unbusy(host, timeout);
}
@@ -743,7 +772,11 @@
return -EIO;
}
- if (host->mmc->use_spi_crc) {
+ /* Omitt the CRC check for CID and CSD reads. There are some SDHC
+ cards which don't supply a valid CRC after CID reads.
+ Note that the CID has it's own CRC7 value inside the data block.
+ */
+ if (host->mmc->use_spi_crc && (t->len == MMC_SPI_BLOCKSIZE)) {
u16 crc = crc_itu_t(0, t->rx_buf, t->len);
be16_to_cpus(&scratch->crc_val);
@@ -1206,8 +1239,15 @@
* rising edge ... meaning SPI modes 0 or 3. So either SPI mode
* should be legit. We'll use mode 0 since it seems to be a
* bit less troublesome on some hardware ... unclear why.
- */
- spi->mode = SPI_MODE_0;
+ *
+ * If the platform_data specifies mode 3, trust the platform_data
+ * and use this one. This allows for platforms which do not support
+ * mode 0.
+ */
+ if (spi->mode != SPI_MODE_3)
+ /* set our default */
+ spi->mode = SPI_MODE_0;
+
spi->bits_per_word = 8;
status = spi_setup(spi);
========= snip ============================
best regards
i. A. Wolfgang Mües
--
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E-Mail: Wolfgang.Mues@...rswald.de
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