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Commit 1a41313e authored by Kyungsik Lee's avatar Kyungsik Lee Committed by Chris Ball
Browse files

mmc: core: Remove bounce buffer in mmc_send_cxd_data() 



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(). It will provide a better
performance gain by removing memcpy() overhead for a half KiB and
a redundant bounce buffer allocated repeatedly at the cost of providing
DMA-capable buffer from upper caller (but on-stack buffer is allowed
with no performance gain).

Signed-off-by: default avatarKyungsik Lee <kyungsik.lee@lge.com>
Reviewed-by: default avatarVenkatraman S <svenkatr@ti.com>
Signed-off-by: default avatarChris Ball <cjb@laptop.org>
parent 8f63795c

drivers/mmc/core/mmc_ops.c

+42 −16
Original line number Diff line number Diff line
@@ -230,6 +230,10 @@ mmc_send_cxd_native(struct mmc_host *host, u32 arg, u32 *cxd, int opcode) 
	return 0;

}



/*

 * NOTE: void *buf, caller for the buf is required to use DMA-capable

 * buffer or on-stack buffer (with some overhead in callee).

 */

static int

mmc_send_cxd_data(struct mmc_card *card, struct mmc_host *host,

		u32 opcode, void *buf, unsigned len)
@@ -239,13 +243,19 @@ 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

	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)

		if (!data_buf)

			return -ENOMEM;

	} else

		data_buf = buf;



	mrq.cmd = &cmd;

	mrq.data = &data;
@@ -280,8 +290,10 @@ mmc_send_cxd_data(struct mmc_card *card, struct mmc_host *host, 


	mmc_wait_for_req(host, &mrq);



	if (is_on_stack) {

		memcpy(buf, data_buf, len);

		kfree(data_buf);

	}



	if (cmd.error)

		return cmd.error;
@@ -294,24 +306,32 @@ 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;



	for (i = 0;i < 4;i++)

		csd[i] = be32_to_cpu(csd[i]);

		csd[i] = be32_to_cpu(csd_tmp[i]);



	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 +340,20 @@ 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;



	for (i = 0;i < 4;i++)

		cid[i] = be32_to_cpu(cid[i]);

		cid[i] = be32_to_cpu(cid_tmp[i]);



	return 0;

err:

	kfree(cid_tmp);

	return ret;

}



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