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    SubjectRe: [PATCH RESEND v3] mmc: core: Remove bounce buffer in mmc_send_cxd_data()
    On 2012-07-31 오후 4:19, S, Venkatraman wrote:
    > On Tue, Jul 31, 2012 at 7:30 AM, Kyungsik Lee <kyungsik.lee@lge.com> wrote:
    >> 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@lge.com>
    >> ---
    >> Changes in v2:
    >> - Handling on-stack buffer if it's used in caller.
    >>
    >> Changes in v3:
    >> - Remove unnecesary code.
    >> ---
    >> drivers/mmc/core/mmc_ops.c | 54 ++++++++++++++++++++++++++++++++-----------
    >> 1 files changed, 40 insertions(+), 14 deletions(-)
    >>
    >> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
    >> index 0ed2cc5..036e6d5 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 +302,34 @@ 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);
    > Can this memcpy be folded into the for loop below
    > as for (....) { csd[i] = be32_to_cpu(csd_tmp[i]); ?
    Yes, you're right. I will fix it as you suggested.

    Thanks,
    Kyungsik Lee
    >> for (i = 0;i < 4;i++)
    >> csd[i] = be32_to_cpu(csd[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 +338,22 @@ 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);
    >>
    > <Same comment as above>
    >
    >> for (i = 0;i < 4;i++)
    >> cid[i] = be32_to_cpu(cid[i]);
    >>
    >> - 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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