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Message-ID: <DM6PR04MB6575686B680A115571EBB015FC539@DM6PR04MB6575.namprd04.prod.outlook.com>
Date: Tue, 11 May 2021 10:40:41 +0000
From: Avri Altman <Avri.Altman@....com>
To: Ulf Hansson <ulf.hansson@...aro.org>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
Adrian Hunter <adrian.hunter@...el.com>
CC: Linus Walleij <linus.walleij@...aro.org>,
Wolfram Sang <wsa+renesas@...g-engineering.com>,
Shawn Lin <shawn.lin@...k-chips.com>,
Masami Hiramatsu <masami.hiramatsu@...aro.org>,
"linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] mmc: core: Add support for cache ctrl for SD cards
> In SD spec v6.x the SD function extension registers for performance
> enhancements were introduced. As a part of this an optional internal cache
> on the SD card, can be used to improve performance.
>
> The let the SD card use the cache, the host needs to enable it and manage
> flushing of the cache, so let's add support for this.
>
> Note that for an SD card supporting the cache it's mandatory for it, to
> also support the poweroff notification feature. According to the SD spec,
> if the cache has been enabled and a poweroff notification is sent to the
> card, that implicitly also means that the card should flush its internal
> cache. Therefore, dealing with cache flushing for REQ_OP_FLUSH block
> requests is sufficient.
>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Reviewed-by: Avri Altman <avri.altman@....com>
> ---
>
> Changes in v2:
> - Converted to use the BIT() macro for clarification, as suggested by Linus.
> - Reset SD_EXT_PERF_CACHE bit when cache enable fails, as suggested by
> Avri.
>
> Note that:
> - I decided to keep the error path when failing to enable the cache. It's
> seems more robust, as it's unclear what happens with the SD card at failure.
> Additionally, if improvements are needed we can make it on top.
>
> ---
> drivers/mmc/core/mmc_ops.c | 1 +
> drivers/mmc/core/mmc_ops.h | 1 +
> drivers/mmc/core/sd.c | 100
> +++++++++++++++++++++++++++++++++++++
> include/linux/mmc/card.h | 1 +
> 4 files changed, 103 insertions(+)
>
> diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
> index af423acc4c88..3c58f6d0f482 100644
> --- a/drivers/mmc/core/mmc_ops.c
> +++ b/drivers/mmc/core/mmc_ops.c
> @@ -456,6 +456,7 @@ static int mmc_busy_cb(void *cb_data, bool *busy)
> err = R1_STATUS(status) ? -EIO : 0;
> break;
> case MMC_BUSY_HPI:
> + case MMC_BUSY_EXTR_SINGLE:
> break;
> default:
> err = -EINVAL;
> diff --git a/drivers/mmc/core/mmc_ops.h b/drivers/mmc/core/mmc_ops.h
> index c3c1d9c2577e..41ab4f573a31 100644
> --- a/drivers/mmc/core/mmc_ops.h
> +++ b/drivers/mmc/core/mmc_ops.h
> @@ -14,6 +14,7 @@ enum mmc_busy_cmd {
> MMC_BUSY_CMD6,
> MMC_BUSY_ERASE,
> MMC_BUSY_HPI,
> + MMC_BUSY_EXTR_SINGLE,
> };
>
> struct mmc_host;
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index bd40c682d264..781c1e24308c 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -67,6 +67,7 @@ static const unsigned int sd_au_size[] = {
> })
>
> #define SD_POWEROFF_NOTIFY_TIMEOUT_MS 2000
> +#define SD_WRITE_EXTR_SINGLE_TIMEOUT_MS 1000
>
> struct sd_busy_data {
> struct mmc_card *card;
> @@ -1287,6 +1288,96 @@ static int sd_read_ext_regs(struct mmc_card
> *card)
> return err;
> }
>
> +static bool sd_cache_enabled(struct mmc_host *host)
> +{
> + return host->card->ext_perf.feature_enabled & SD_EXT_PERF_CACHE;
> +}
> +
> +static int sd_flush_cache(struct mmc_host *host)
> +{
> + struct mmc_card *card = host->card;
> + u8 *reg_buf, fno, page;
> + u16 offset;
> + int err;
> +
> + if (!sd_cache_enabled(host))
> + return 0;
> +
> + reg_buf = kzalloc(512, GFP_KERNEL);
> + if (!reg_buf)
> + return -ENOMEM;
> +
> + /*
> + * Set Flush Cache at bit 0 in the performance enhancement register at
> + * 261 bytes offset.
> + */
> + fno = card->ext_perf.fno;
> + page = card->ext_perf.page;
> + offset = card->ext_perf.offset + 261;
> +
> + err = sd_write_ext_reg(card, fno, page, offset, BIT(0));
> + if (err) {
> + pr_warn("%s: error %d writing Cache Flush bit\n",
> + mmc_hostname(host), err);
> + goto out;
> + }
> +
> + err = mmc_poll_for_busy(card,
> SD_WRITE_EXTR_SINGLE_TIMEOUT_MS, false,
> + MMC_BUSY_EXTR_SINGLE);
> + if (err)
> + goto out;
> +
> + /*
> + * Read the Flush Cache bit. The card shall reset it, to confirm that
> + * it's has completed the flushing of the cache.
> + */
> + err = sd_read_ext_reg(card, fno, page, offset, 1, reg_buf);
> + if (err) {
> + pr_warn("%s: error %d reading Cache Flush bit\n",
> + mmc_hostname(host), err);
> + goto out;
> + }
> +
> + if (reg_buf[0] & BIT(0))
> + err = -ETIMEDOUT;
> +out:
> + kfree(reg_buf);
> + return err;
> +}
> +
> +static int sd_enable_cache(struct mmc_card *card)
> +{
> + u8 *reg_buf;
> + int err;
> +
> + card->ext_perf.feature_enabled &= ~SD_EXT_PERF_CACHE;
> +
> + reg_buf = kzalloc(512, GFP_KERNEL);
> + if (!reg_buf)
> + return -ENOMEM;
> +
> + /*
> + * Set Cache Enable at bit 0 in the performance enhancement register at
> + * 260 bytes offset.
> + */
> + err = sd_write_ext_reg(card, card->ext_perf.fno, card->ext_perf.page,
> + card->ext_perf.offset + 260, BIT(0));
> + if (err) {
> + pr_warn("%s: error %d writing Cache Enable bit\n",
> + mmc_hostname(card->host), err);
> + goto out;
> + }
> +
> + err = mmc_poll_for_busy(card,
> SD_WRITE_EXTR_SINGLE_TIMEOUT_MS, false,
> + MMC_BUSY_EXTR_SINGLE);
> + if (!err)
> + card->ext_perf.feature_enabled |= SD_EXT_PERF_CACHE;
> +
> +out:
> + kfree(reg_buf);
> + return err;
> +}
> +
> /*
> * Handle the detection and initialisation of a card.
> *
> @@ -1442,6 +1533,13 @@ static int mmc_sd_init_card(struct mmc_host
> *host, u32 ocr,
> goto free_card;
> }
>
> + /* Enable internal SD cache if supported. */
> + if (card->ext_perf.feature_support & SD_EXT_PERF_CACHE) {
> + err = sd_enable_cache(card);
> + if (err)
> + goto free_card;
> + }
> +
> if (host->cqe_ops && !host->cqe_enabled) {
> err = host->cqe_ops->cqe_enable(host, card);
> if (!err) {
> @@ -1694,6 +1792,8 @@ static const struct mmc_bus_ops mmc_sd_ops = {
> .alive = mmc_sd_alive,
> .shutdown = mmc_sd_suspend,
> .hw_reset = mmc_sd_hw_reset,
> + .cache_enabled = sd_cache_enabled,
> + .flush_cache = sd_flush_cache,
> };
>
> /*
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index 2867af0635f8..74e6c0624d27 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -196,6 +196,7 @@ struct sd_ext_reg {
> u8 page;
> u16 offset;
> u8 rev;
> + u8 feature_enabled;
> u8 feature_support;
> /* Power Management Function. */
> #define SD_EXT_POWER_OFF_NOTIFY (1<<0)
> --
> 2.25.1
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