mmc,sdio: helper function for transfer padding
There are a lot of crappy controllers out there that cannot handle
all the request sizes that the MMC/SD/SDIO specifications require.
In case the card driver can pad the data to overcome the problems,
this commit adds a helper that calculates how much that padding
should be.
A corresponding helper is also added for SDIO, but it can also deal
with all the complexities of splitting up a large transfer efficiently.
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
diff --git a/drivers/mmc/core/sdio_io.c b/drivers/mmc/core/sdio_io.c
index 625b92c..6ee7861 100644
--- 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 @@
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,