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@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Link: https://lore.kernel.org/r/20210511101359.83521-1-ulf.hansson@linaro.org

diff --git a/drivers/mmc/core/mmc_ops.c b/drivers/mmc/core/mmc_ops.c
index af423acc4c88585ca4ccb67e22430b9b3e05874f..3c58f6d0f48211cccca07353f17411fabf947583 100644 (file)
--- 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 c3c1d9c2577e6c77506df5fe491be988afee56d6..41ab4f573a310dd1c805b80ad4056711d4a14670 100644 (file)
--- 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 bd40c682d264499523a5eb3bf75027d92a2015ac..781c1e24308c81600c60d5be289efb116f0ce9d7 100644 (file)
--- 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 @@ out:
        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 @@ retry:
                        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 2867af0635f8bebb604c38a3e4d4fff28ba53af5..74e6c0624d2779badee5e6f55f7a3bc8bd9987ba 100644 (file)
--- 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)