mmc,sdio: helper function for transfer padding

[karo-tx-linux.git] / drivers / mmc / core / sdio_io.c

diff --git a/drivers/mmc/core/sdio_io.c b/drivers/mmc/core/sdio_io.c
index 625b92ce9cef2abedbaf853f2e0d2ba6dc7a7314..6ee7861fceae96b49ac8ffbbeda28c4bc3d65c45 100644 (file)
--- a/drivers/mmc/core/sdio_io.c
+++ b/drivers/mmc/core/sdio_io.c
@@ -1,7 +1,7 @@
 /*
  *  linux/drivers/mmc/core/sdio_io.c
  *
- *  Copyright 2007 Pierre Ossman
+ *  Copyright 2007-2008 Pierre Ossman
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -189,6 +189,103 @@ int sdio_set_block_size(struct sdio_func *func, unsigned blksz)
 
 EXPORT_SYMBOL_GPL(sdio_set_block_size);
 
+/**
+ *     sdio_align_size - pads a transfer size to a more optimal value
+ *     @func: SDIO function
+ *     @sz: original transfer size
+ *
+ *     Pads the original data size with a number of extra bytes in
+ *     order to avoid controller bugs and/or performance hits
+ *     (e.g. some controllers revert to PIO for certain sizes).
+ *
+ *     If possible, it will also adjust the size so that it can be
+ *     handled in just a single request.
+ *
+ *     Returns the improved size, which might be unmodified.
+ */
+unsigned int sdio_align_size(struct sdio_func *func, unsigned int sz)
+{
+       unsigned int orig_sz;
+       unsigned int blk_sz, byte_sz;
+       unsigned chunk_sz;
+
+       orig_sz = sz;
+
+       /*
+        * Do a first check with the controller, in case it
+        * wants to increase the size up to a point where it
+        * might need more than one block.
+        */
+       sz = mmc_align_data_size(func->card, sz);
+
+       /*
+        * If we can still do this with just a byte transfer, then
+        * we're done.
+        */
+       if ((sz <= func->cur_blksize) && (sz <= 512))
+               return sz;
+
+       if (func->card->cccr.multi_block) {
+               /*
+                * Check if the transfer is already block aligned
+                */
+               if ((sz % func->cur_blksize) == 0)
+                       return sz;
+
+               /*
+                * Realign it so that it can be done with one request,
+                * and recheck if the controller still likes it.
+                */
+               blk_sz = ((sz + func->cur_blksize - 1) /
+                       func->cur_blksize) * func->cur_blksize;
+               blk_sz = mmc_align_data_size(func->card, blk_sz);
+
+               /*
+                * This value is only good if it is still just
+                * one request.
+                */
+               if ((blk_sz % func->cur_blksize) == 0)
+                       return blk_sz;
+
+               /*
+                * We failed to do one request, but at least try to
+                * pad the remainder properly.
+                */
+               byte_sz = mmc_align_data_size(func->card,
+                               sz % func->cur_blksize);
+               if ((byte_sz <= func->cur_blksize) && (byte_sz <= 512)) {
+                       blk_sz = sz / func->cur_blksize;
+                       return blk_sz * func->cur_blksize + byte_sz;
+               }
+       } else {
+               /*
+                * We need multiple requests, so first check that the
+                * controller can handle the chunk size;
+                */
+               chunk_sz = mmc_align_data_size(func->card,
+                               min(func->cur_blksize, 512u));
+               if (chunk_sz == min(func->cur_blksize, 512u)) {
+                       /*
+                        * Fix up the size of the remainder (if any)
+                        */
+                       byte_sz = orig_sz % chunk_sz;
+                       if (byte_sz) {
+                               byte_sz = mmc_align_data_size(func->card,
+                                               byte_sz);
+                       }
+
+                       return (orig_sz / chunk_sz) * chunk_sz + byte_sz;
+               }
+       }
+
+       /*
+        * The controller is simply incapable of transferring the size
+        * we want in decent manner, so just return the original size.
+        */
+       return orig_sz;
+}
+EXPORT_SYMBOL_GPL(sdio_align_size);
+
 /* Split an arbitrarily sized data transfer into several
  * IO_RW_EXTENDED commands. */
 static int sdio_io_rw_ext_helper(struct sdio_func *func, int write,