MMC core learns about SPI

Teach the MMC/SD/SDIO core about using SPI mode.

 - Use mmc_host_is_spi() so enumeration works through SPI signaling
   and protocols, not just the native versions.

 - Provide the SPI response type flags with each request issued,
   including requests from the new lock/unlock code.

 - Understand that cmd->resp[0] and mmc_get_status() results for SPI
   return different values than for "native" MMC/SD protocol; this
   affects resetting, checking card lock status, and some others.

 - Understand that some commands act a bit differently ... notably:
     * OP_COND command doesn't return the OCR
     * APP_CMD status doesn't have an R1_APP_CMD analogue

Those changes required some new and updated primitives:

 - Provide utilities to access two SPI-only requests, and one
   request that wasn't previously needed:
     * mmc_spi_read_ocr() ... SPI only
     * mmc_spi_set_crc() ... SPI only (override by module parm)
     * mmc_send_cid() ... for use without broadcast mode

 - Updated internal routines:
     * Previous mmc_send_csd() modified into mmc_send_cxd_native();
       it uses native "R2" responses, which include 16 bytes of data.
     * Previous mmc_send_ext_csd() becomes new mmc_send_cxd_data()
       helper for command-and-data access
     * Bugfix to that mmc_send_cxd_data() code:  dma-to-stack is
       unsafe/nonportable, so kmalloc a bounce buffer instead.

 - Modified mmc_send_ext_csd() now uses mmc_send_cxd_data() helper

 - Modified mmc_send_csd(), and new mmc_spi_send_cid(), routines use
   those helper routines based on whether they're native or SPI

The newest categories of cards supported by the MMC stack aren't expected
to work yet with SPI:  MMC or SD cards with over 4GB data, and SDIO.
All those cards support SPI mode, so eventually they should work too.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

1 files changed, 24 insertions, 4 deletions

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index bffcaf8df352..bad39442f8fe 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -42,6 +42,14 @@ extern int mmc_attach_sdio(struct mmc_host *host, u32 ocr);
 static struct workqueue_struct *workqueue;
 
 /*
+ * Enabling software CRCs on the data blocks can be a significant (30%)
+ * performance cost, and for other reasons may not always be desired.
+ * So we allow it it to be disabled.
+ */
+int use_spi_crc = 1;
+module_param(use_spi_crc, bool, 0);
+
+/*
  * Internal function. Schedule delayed work in the MMC work queue.
  */
 static int mmc_schedule_delayed_work(struct delayed_work *work,
@@ -71,6 +79,11 @@ void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
         struct mmc_command *cmd = mrq->cmd;
         int err = cmd->error;
 
+        if (err && cmd->retries && mmc_host_is_spi(host)) {
+                if (cmd->resp[0] & R1_SPI_ILLEGAL_COMMAND)
+                        cmd->retries = 0;
+        }
+
         if (err && cmd->retries) {
                 pr_debug("%s: req failed (CMD%u): %d, retrying...\n",
                         mmc_hostname(host), cmd->opcode, err);
@@ -453,8 +466,13 @@ static void mmc_power_up(struct mmc_host *host)
         int bit = fls(host->ocr_avail) - 1;
 
         host->ios.vdd = bit;
-        host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
-        host->ios.chip_select = MMC_CS_DONTCARE;
+        if (mmc_host_is_spi(host)) {
+                host->ios.chip_select = MMC_CS_HIGH;
+                host->ios.bus_mode = MMC_BUSMODE_PUSHPULL;
+        } else {
+                host->ios.chip_select = MMC_CS_DONTCARE;
+                host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
+        }
         host->ios.power_mode = MMC_POWER_UP;
         host->ios.bus_width = MMC_BUS_WIDTH_1;
         host->ios.timing = MMC_TIMING_LEGACY;
@@ -481,8 +499,10 @@ static void mmc_power_off(struct mmc_host *host)
 {
         host->ios.clock = 0;
         host->ios.vdd = 0;
-        host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
-        host->ios.chip_select = MMC_CS_DONTCARE;
+        if (!mmc_host_is_spi(host)) {
+                host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
+                host->ios.chip_select = MMC_CS_DONTCARE;
+        }
         host->ios.power_mode = MMC_POWER_OFF;
         host->ios.bus_width = MMC_BUS_WIDTH_1;
         host->ios.timing = MMC_TIMING_LEGACY;