mmc: sdhci: allow drivers to pre-allocate bounce buffer

Allow platform drivers to pre-allocate bounce buffer by checking if
host->bounce_buffer is already set before attempting allocation.

This enables platforms with specific DMA constraints (such as 32-bit
DMA on controllers that cannot access high memory) to use their own
reserved memory regions for the bounce buffer.

Suggested-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Albert Yang <yangzh0906@thundersoft.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 1ff15fa9b042e6b7dcf4bbc7ca54c84ce25ce25d..b1a3cd574c841470513a7ed359343572d6881444 100644 (file)
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -4193,6 +4193,12 @@ static void sdhci_allocate_bounce_buffer(struct sdhci_host *host)
        unsigned int bounce_size;
        int ret;
 
+       /* Drivers may have already allocated the buffer */
+       if (host->bounce_buffer) {
+               bounce_size = host->bounce_buffer_size;
+               max_blocks = bounce_size / 512;
+               goto out;
+       }
        /*
         * Cap the bounce buffer at 64KB. Using a bigger bounce buffer
         * has diminishing returns, this is probably because SD/MMC
@@ -4241,6 +4247,7 @@ static void sdhci_allocate_bounce_buffer(struct sdhci_host *host)
 
        host->bounce_buffer_size = bounce_size;
 
+out:
        /* Lie about this since we're bouncing */
        mmc->max_segs = max_blocks;
        mmc->max_seg_size = bounce_size;