[PATCH RESEND v2] mmc: core: Remove bounce buffer in mmc_send_cxd_data()

From: Kyungsik Lee
Date: Sun Jul 29 2012 - 22:04:39 EST


It is expected that Extended CSD register(the size of this register
is larger than CID/CSD) will be referenced more frequently as more
fields have been added to Extended CSD and it seems that it is not
a good option to double the memory used.

This patch is intended to avoid the use of bounce buffer for reading
Extended CSD register in mmc_send_cxd_data().

Signed-off-by: Kyungsik Lee <kyungsik.lee@xxxxxxx>
---
Changes in v2:
- Handling on-stack buffer if it's used in caller.
---
drivers/mmc/core/mmc_ops.c | 56 ++++++++++++++++++++++++++++++++++---------
1 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
index 0ed2cc5..dae5492 100644
--- a/drivers/mmc/core/mmc_ops.c
+++ b/drivers/mmc/core/mmc_ops.c
@@ -239,13 +239,19 @@ mmc_send_cxd_data(struct mmc_card *card, struct mmc_host *host,
struct mmc_data data = {0};
struct scatterlist sg;
void *data_buf;
+ int is_on_stack;

- /* dma onto stack is unsafe/nonportable, but callers to this
- * routine normally provide temporary on-stack buffers ...
- */
- data_buf = kmalloc(len, GFP_KERNEL);
- if (data_buf == NULL)
- return -ENOMEM;
+ is_on_stack = object_is_on_stack(buf);
+ if (is_on_stack) {
+
+ /* dma onto stack is unsafe/nonportable, but callers to this
+ * routine normally provide temporary on-stack buffers ...
+ */
+ data_buf = kmalloc(len, GFP_KERNEL);
+ if (data_buf == NULL)
+ return -ENOMEM;
+ } else
+ data_buf = buf;

mrq.cmd = &cmd;
mrq.data = &data;
@@ -280,8 +286,10 @@ mmc_send_cxd_data(struct mmc_card *card, struct mmc_host *host,

mmc_wait_for_req(host, &mrq);

- memcpy(buf, data_buf, len);
- kfree(data_buf);
+ if (is_on_stack) {
+ memcpy(buf, data_buf, len);
+ kfree(data_buf);
+ }

if (cmd.error)
return cmd.error;
@@ -294,24 +302,37 @@ mmc_send_cxd_data(struct mmc_card *card, struct mmc_host *host,
int mmc_send_csd(struct mmc_card *card, u32 *csd)
{
int ret, i;
+ u32 *csd_tmp;

if (!mmc_host_is_spi(card->host))
return mmc_send_cxd_native(card->host, card->rca << 16,
csd, MMC_SEND_CSD);

- ret = mmc_send_cxd_data(card, card->host, MMC_SEND_CSD, csd, 16);
+ csd_tmp = kmalloc(16, GFP_KERNEL);
+ if (!csd_tmp)
+ return -ENOMEM;
+
+ ret = mmc_send_cxd_data(card, card->host, MMC_SEND_CSD, csd_tmp, 16);
if (ret)
- return ret;
+ goto err;
+
+ memcpy(csd, csd_tmp, 16);

for (i = 0;i < 4;i++)
csd[i] = be32_to_cpu(csd[i]);

+ kfree(csd_tmp);
return 0;
+
+err:
+ kfree(csd_tmp);
+ return ret;
}

int mmc_send_cid(struct mmc_host *host, u32 *cid)
{
int ret, i;
+ u32 *cid_tmp;

if (!mmc_host_is_spi(host)) {
if (!host->card)
@@ -320,14 +341,25 @@ int mmc_send_cid(struct mmc_host *host, u32 *cid)
cid, MMC_SEND_CID);
}

- ret = mmc_send_cxd_data(NULL, host, MMC_SEND_CID, cid, 16);
+ cid_tmp = kmalloc(16, GFP_KERNEL);
+ if (!cid_tmp)
+ return -ENOMEM;
+
+ ret = mmc_send_cxd_data(NULL, host, MMC_SEND_CID, cid_tmp, 16);
if (ret)
- return ret;
+ goto err;
+
+ memcpy(cid, cid_tmp, 16);

for (i = 0;i < 4;i++)
cid[i] = be32_to_cpu(cid[i]);

+ kfree(cid_tmp);
return 0;
+
+err:
+ kfree(cid_tmp);
+ return ret;
}

int mmc_send_ext_csd(struct mmc_card *card, u8 *ext_csd)
--
1.7.0.4

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