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Commit 968a64ea638bbd48839b41981ff50197f3412676

Authored by Kyoungil Kim
Committed by Chris Ball
1 parent 8fee476b21
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

mmc: sdio: Use multiple scatter/gather list 

Before this patch, we always used only single sg entry for SDIO transfer.
This patch switches to using multiple sg entries. In the case of dwmci,
it supports only up to 4KB size per single sg entry. So if we want to
transfer more than 4KB, we should send more than 1 command.

When we tested before applying this patch, it took around 335 us for
5K(5120) bytes transfer with dwmci controller. After applying this patch,
it takes 242 us for 5K bytes. So this patch makes around 38% performance
improvement for 5K bytes transfer. If the transfer size is bigger, then
the performance improvement ratio will be increased.

Signed-off-by: Kyoungil Kim <ki0351.kim@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

Showing 2 changed files with 31 additions and 11 deletions Side-by-side Diff

drivers/mmc/core/sdio_io.c
Diff comments   View file @ 968a64e
... ... @@ -188,8 +188,7 @@
188 188 */
189 189 static inline unsigned int sdio_max_byte_size(struct sdio_func *func)
190 190 {
191   - unsigned mval = min(func->card->host->max_seg_size,
192   - func->card->host->max_blk_size);
  191 + unsigned mval = func->card->host->max_blk_size;
193 192  
194 193 if (mmc_blksz_for_byte_mode(func->card))
195 194 mval = min(mval, func->cur_blksize);
... ... @@ -311,11 +310,8 @@
311 310 /* Do the bulk of the transfer using block mode (if supported). */
312 311 if (func->card->cccr.multi_block && (size > sdio_max_byte_size(func))) {
313 312 /* Blocks per command is limited by host count, host transfer
314   - * size (we only use a single sg entry) and the maximum for
315   - * IO_RW_EXTENDED of 511 blocks. */
316   - max_blocks = min(func->card->host->max_blk_count,
317   - func->card->host->max_seg_size / func->cur_blksize);
318   - max_blocks = min(max_blocks, 511u);
  313 + * size and the maximum for IO_RW_EXTENDED of 511 blocks. */
  314 + max_blocks = min(func->card->host->max_blk_count, 511u);
319 315  
320 316 while (remainder >= func->cur_blksize) {
321 317 unsigned blocks;
drivers/mmc/core/sdio_ops.c
Diff comments   View file @ 968a64e
... ... @@ -124,7 +124,10 @@
124 124 struct mmc_request mrq = {NULL};
125 125 struct mmc_command cmd = {0};
126 126 struct mmc_data data = {0};
127   - struct scatterlist sg;
  127 + struct scatterlist sg, *sg_ptr;
  128 + struct sg_table sgtable;
  129 + unsigned int nents, left_size, i;
  130 + unsigned int seg_size = card->host->max_seg_size;
128 131  
129 132 BUG_ON(!card);
130 133 BUG_ON(fn > 7);
131 134  
132 135  
133 136  
... ... @@ -152,14 +155,35 @@
152 155 /* Code in host drivers/fwk assumes that "blocks" always is >=1 */
153 156 data.blocks = blocks ? blocks : 1;
154 157 data.flags = write ? MMC_DATA_WRITE : MMC_DATA_READ;
155   - data.sg = &sg;
156   - data.sg_len = 1;
157 158  
158   - sg_init_one(&sg, buf, data.blksz * data.blocks);
  159 + left_size = data.blksz * data.blocks;
  160 + nents = (left_size - 1) / seg_size + 1;
  161 + if (nents > 1) {
  162 + if (sg_alloc_table(&sgtable, nents, GFP_KERNEL))
  163 + return -ENOMEM;
159 164  
  165 + data.sg = sgtable.sgl;
  166 + data.sg_len = nents;
  167 +
  168 + for_each_sg(data.sg, sg_ptr, data.sg_len, i) {
  169 + sg_set_page(sg_ptr, virt_to_page(buf + (i * seg_size)),
  170 + min(seg_size, left_size),
  171 + offset_in_page(buf + (i * seg_size)));
  172 + left_size = left_size - seg_size;
  173 + }
  174 + } else {
  175 + data.sg = &sg;
  176 + data.sg_len = 1;
  177 +
  178 + sg_init_one(&sg, buf, left_size);
  179 + }
  180 +
160 181 mmc_set_data_timeout(&data, card);
161 182  
162 183 mmc_wait_for_req(card->host, &mrq);
  184 +
  185 + if (nents > 1)
  186 + sg_free_table(&sgtable);
163 187  
164 188 if (cmd.error)
165 189 return cmd.error;