drivers: Remove explicit invocations of mmiowb()

[linux.git] / drivers / mmc / host / alcor.c

diff --git a/drivers/mmc/host/alcor.c b/drivers/mmc/host/alcor.c
index c712b7deb3a9d88e62416005d2444e908a4fb664..546b1fc30e7d812d050c05570e670de07f5f780b 100644 (file)
--- a/drivers/mmc/host/alcor.c
+++ b/drivers/mmc/host/alcor.c
@@ -967,7 +967,6 @@ static void alcor_timeout_timer(struct work_struct *work)
                alcor_request_complete(host, 0);
        }
 
-       mmiowb();
        mutex_unlock(&host->cmd_mutex);
 }
 
@@ -1044,14 +1043,27 @@ static void alcor_init_mmc(struct alcor_sdmmc_host *host)
        mmc->caps2 = MMC_CAP2_NO_SDIO;
        mmc->ops = &alcor_sdc_ops;
 
-       /* Hardware cannot do scatter lists */
+       /* The hardware does DMA data transfer of 4096 bytes to/from a single
+        * buffer address. Scatterlists are not supported, but upon DMA
+        * completion (signalled via IRQ), the original vendor driver does
+        * then immediately set up another DMA transfer of the next 4096
+        * bytes.
+        *
+        * This means that we need to handle the I/O in 4096 byte chunks.
+        * Lacking a way to limit the sglist entries to 4096 bytes, we instead
+        * impose that only one segment is provided, with maximum size 4096,
+        * which also happens to be the minimum size. This means that the
+        * single-entry sglist handled by this driver can be handed directly
+        * to the hardware, nice and simple.
+        *
+        * Unfortunately though, that means we only do 4096 bytes I/O per
+        * MMC command. A future improvement would be to make the driver
+        * accept sg lists and entries of any size, and simply iterate
+        * through them 4096 bytes at a time.
+        */
        mmc->max_segs = AU6601_MAX_DMA_SEGMENTS;
        mmc->max_seg_size = AU6601_MAX_DMA_BLOCK_SIZE;
-
-       mmc->max_blk_size = mmc->max_seg_size;
-       mmc->max_blk_count = mmc->max_segs;
-
-       mmc->max_req_size = mmc->max_seg_size * mmc->max_segs;
+       mmc->max_req_size = mmc->max_seg_size;
 }
 
 static int alcor_pci_sdmmc_drv_probe(struct platform_device *pdev)