Messages in this thread | | | Date | Thu, 02 Aug 2012 14:39:39 +0900 | From | "kyungsik.lee" <> | Subject | Re: [PATCH RESEND v4] mmc: core: Remove bounce buffer in mmc_send_cxd_data() |
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Hello Chanho Min,
On 2012-08-02 오전 11:50, Chanho Min wrote: >> -----Original Message----- >> From: Kyungsik Lee [mailto:kyungsik.lee@lge.com] >> Sent: Wednesday, August 01, 2012 10:06 AM >> To: Chris Ball >> Cc: Venkatraman S; Jaehoon Chung; raphael.andy.lee@gmail.com; linux- >> mmc@vger.kernel.org; linux-kernel@vger.kernel.org; Kyungsik Lee >> Subject: [PATCH RESEND v4] 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(). >> >> Signed-off-by: Kyungsik Lee <kyungsik.lee@lge.com> >> Signed-off-by: S, Venkatraman <svenkatr@ti.com> >> --- >> Changes in v2: >> - Handling on-stack buffer if it's used in caller. >> >> Changes in v3: >> - Remove unnecesary code. >> >> Changes in v4: >> - Modify codes based-on S, Venkatraman's comments. >> --- >> drivers/mmc/core/mmc_ops.c | 54 > +++++++++++++++++++++++++++++++------------ >> - >> 1 files changed, 38 insertions(+), 16 deletions(-) >> >> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c >> index 0ed2cc5..920a017 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 +302,32 @@ 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; >> } > If we can handle for the on-stack buffer in mmc_send_cxd_data, why do we > need callers's modification as bellows? As you comment above, on-stack buffer can be handled with no better performance gain. In case of both mmc_send_cid() and mmc_send_csd(), on-stack buffers have not been allocated in the upper callers to the two functions(you may check it in the upper callers). And you will find out the reason why such a modification below is needed in the mail thread (Reply to S, Venkatraman's comment).
Thanks Kyungsik Lee >> 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 +336,20 @@ 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) >> -- >> 1.7.0.4 > Thanks > Chanho Min > >
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