scsi: ufs: core: Allow RTT negotiation

The rtt-upiu packets precede any data-out upiu packets, thus synchronizing
the data input to the device: this mostly applies to write operations, but
there are other operations that requires rtt as well.

There are several rules binding this rtt - data-out dialog, specifically
There can be at most outstanding bMaxNumOfRTT such packets.  This might
have an effect on write performance (sequential write in particular), as
each data-out upiu must wait for its rtt sibling.

UFSHCI expects bMaxNumOfRTT to be min(bDeviceRTTCap, NORTT). However, as of
today, there does not appears to be no-one who sets it: not the host
controller nor the driver.  It wasn't an issue up to now: bMaxNumOfRTT is
set to 2 after manufacturing, and wasn't limiting the write performance.

UFS4.0, and specifically gear 5 changes this, and requires the device to be
more attentive.  This doesn't come free - the device has to allocate more
resources to that end, but the sequential write performance improvement is
significant. Early measurements shows 25% gain when moving from rtt 2 to
9. Therefore, set bMaxNumOfRTT to be min(bDeviceRTTCap, NORTT) as UFSHCI
expects.

Signed-off-by: Avri Altman <avri.altman@wdc.com>
Link: https://lore.kernel.org/r/20240530142510.734-2-avri.altman@wdc.com
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 0cf07194bbe89dfe6d86a78d31c0c0b7fdc63056..dda6d7e44436bddeebaaad5f1fcff733211193c0 100644 (file)
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -102,6 +102,9 @@
 /* Default RTC update every 10 seconds */
 #define UFS_RTC_UPDATE_INTERVAL_MS (10 * MSEC_PER_SEC)
 
+/* bMaxNumOfRTT is equal to two after device manufacturing */
+#define DEFAULT_MAX_NUM_RTT 2
+
 /* UFSHC 4.0 compliant HC support this mode. */
 static bool use_mcq_mode = true;
 
@@ -2405,6 +2408,8 @@ static inline int ufshcd_hba_capabilities(struct ufs_hba *hba)
        ((hba->capabilities & MASK_TASK_MANAGEMENT_REQUEST_SLOTS) >> 16) + 1;
        hba->reserved_slot = hba->nutrs - 1;
 
+       hba->nortt = FIELD_GET(MASK_NUMBER_OUTSTANDING_RTT, hba->capabilities) + 1;
+
        /* Read crypto capabilities */
        err = ufshcd_hba_init_crypto_capabilities(hba);
        if (err) {
@@ -8121,6 +8126,35 @@ out:
        dev_info->b_ext_iid_en = ext_iid_en;
 }
 
+static void ufshcd_set_rtt(struct ufs_hba *hba)
+{
+       struct ufs_dev_info *dev_info = &hba->dev_info;
+       u32 rtt = 0;
+       u32 dev_rtt = 0;
+
+       /* RTT override makes sense only for UFS-4.0 and above */
+       if (dev_info->wspecversion < 0x400)
+               return;
+
+       if (ufshcd_query_attr_retry(hba, UPIU_QUERY_OPCODE_READ_ATTR,
+                                   QUERY_ATTR_IDN_MAX_NUM_OF_RTT, 0, 0, &dev_rtt)) {
+               dev_err(hba->dev, "failed reading bMaxNumOfRTT\n");
+               return;
+       }
+
+       /* do not override if it was already written */
+       if (dev_rtt != DEFAULT_MAX_NUM_RTT)
+               return;
+
+       rtt = min_t(int, dev_info->rtt_cap, hba->nortt);
+       if (rtt == dev_rtt)
+               return;
+
+       if (ufshcd_query_attr_retry(hba, UPIU_QUERY_OPCODE_WRITE_ATTR,
+                                   QUERY_ATTR_IDN_MAX_NUM_OF_RTT, 0, 0, &rtt))
+               dev_err(hba->dev, "failed writing bMaxNumOfRTT\n");
+}
+
 void ufshcd_fixup_dev_quirks(struct ufs_hba *hba,
                             const struct ufs_dev_quirk *fixups)
 {
@@ -8256,6 +8290,8 @@ static int ufs_get_device_desc(struct ufs_hba *hba)
                                      desc_buf[DEVICE_DESC_PARAM_SPEC_VER + 1];
        dev_info->bqueuedepth = desc_buf[DEVICE_DESC_PARAM_Q_DPTH];
 
+       dev_info->rtt_cap = desc_buf[DEVICE_DESC_PARAM_RTT_CAP];
+
        model_index = desc_buf[DEVICE_DESC_PARAM_PRDCT_NAME];
 
        err = ufshcd_read_string_desc(hba, model_index,
@@ -8508,6 +8544,8 @@ static int ufshcd_device_params_init(struct ufs_hba *hba)
                goto out;
        }
 
+       ufshcd_set_rtt(hba);
+
        ufshcd_get_ref_clk_gating_wait(hba);
 
        if (!ufshcd_query_flag_retry(hba, UPIU_QUERY_OPCODE_READ_FLAG,

diff --git a/include/ufs/ufs.h b/include/ufs/ufs.h
index b6003749bc83a2cf582df7681052f0bdd630efc0..853e95957c3120c7fb443703d6c15988b61a346f 100644 (file)
--- a/include/ufs/ufs.h
+++ b/include/ufs/ufs.h
@@ -592,6 +592,8 @@ struct ufs_dev_info {
        enum ufs_rtc_time rtc_type;
        time64_t rtc_time_baseline;
        u32 rtc_update_period;
+
+       u8 rtt_cap; /* bDeviceRTTCap */
 };
 
 /*

diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index bad88bd9199513479d2c321c7e2c5e752d6e0755..d74bd2d67b061c98890806d1891fd914d36a2ee7 100644 (file)
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -819,6 +819,7 @@ enum ufshcd_mcq_opr {
  * @capabilities: UFS Controller Capabilities
  * @mcq_capabilities: UFS Multi Circular Queue capabilities
  * @nutrs: Transfer Request Queue depth supported by controller
+ * @nortt - Max outstanding RTTs supported by controller
  * @nutmrs: Task Management Queue depth supported by controller
  * @reserved_slot: Used to submit device commands. Protected by @dev_cmd.lock.
  * @ufs_version: UFS Version to which controller complies
@@ -957,6 +958,7 @@ struct ufs_hba {
 
        u32 capabilities;
        int nutrs;
+       int nortt;
        u32 mcq_capabilities;
        int nutmrs;
        u32 reserved_slot;

diff --git a/include/ufs/ufshci.h b/include/ufs/ufshci.h
index 385e1c6b8d6046936f7c11fd313993d189d275c0..c50f92bf2e1dfa809f7d9f586028184cf3eb1a9c 100644 (file)
--- a/include/ufs/ufshci.h
+++ b/include/ufs/ufshci.h
@@ -68,6 +68,7 @@ enum {
 /* Controller capability masks */
 enum {
        MASK_TRANSFER_REQUESTS_SLOTS            = 0x0000001F,
+       MASK_NUMBER_OUTSTANDING_RTT             = 0x0000FF00,
        MASK_TASK_MANAGEMENT_REQUEST_SLOTS      = 0x00070000,
        MASK_EHSLUTRD_SUPPORTED                 = 0x00400000,
        MASK_AUTO_HIBERN8_SUPPORT               = 0x00800000,