scsi: ufs: core: Maximum RTT supported by the host driver

Allow platform vendors to take precedence having their own max rtt support.
This makes sense because the host controller's nortt characteristic may
vary among vendors.

while at it, set this value for Mediatek, as requested by Peter -
https://lore.kernel.org/all/0a57d6bab739d6a10584f2baba115d00dfc9c94c.camel@mediatek.com/Signed-off-by: Avri Altman <avri.altman@wdc.com>
Link: https://lore.kernel.org/r/20240530142510.734-3-avri.altman@wdc.comReviewed-by: Peter Wang <peter.wang@mediatek.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/ufs/core/ufshcd.c

@@ -8131,6 +8131,8 @@ 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;
+	int host_rtt_cap = hba->vops && hba->vops->max_num_rtt ?
+			   hba->vops->max_num_rtt : hba->nortt;
 
 	/* RTT override makes sense only for UFS-4.0 and above */
 	if (dev_info->wspecversion < 0x400)
@@ -8146,7 +8148,8 @@ static void ufshcd_set_rtt(struct ufs_hba *hba)
 	if (dev_rtt != DEFAULT_MAX_NUM_RTT)
 		return;
 
-	rtt = min_t(int, dev_info->rtt_cap, hba->nortt);
+	rtt = min_t(int, dev_info->rtt_cap, host_rtt_cap);
+
 	if (rtt == dev_rtt)
 		return;
 

drivers/ufs/host/ufs-mediatek.c

@@ -1785,6 +1785,7 @@ static int ufs_mtk_config_esi(struct ufs_hba *hba)
  */
 static const struct ufs_hba_variant_ops ufs_hba_mtk_vops = {
 	.name                = "mediatek.ufshci",
+	.max_num_rtt         = MTK_MAX_NUM_RTT,
 	.init                = ufs_mtk_init,
 	.get_ufs_hci_version = ufs_mtk_get_ufs_hci_version,
 	.setup_clocks        = ufs_mtk_setup_clocks,

drivers/ufs/host/ufs-mediatek.h

@@ -189,4 +189,7 @@ struct ufs_mtk_host {
 /* MTK delay of autosuspend: 500 ms */
 #define MTK_RPM_AUTOSUSPEND_DELAY_MS 500
 
+/* MTK RTT support number */
+#define MTK_MAX_NUM_RTT 2
+
 #endif /* !_UFS_MEDIATEK_H */

include/ufs/ufshcd.h

@@ -295,6 +295,7 @@ struct ufs_pwr_mode_info {
 /**
  * struct ufs_hba_variant_ops - variant specific callbacks
  * @name: variant name
+ * @max_num_rtt: maximum RTT supported by the host
  * @init: called when the driver is initialized
  * @exit: called to cleanup everything done in init
  * @get_ufs_hci_version: called to get UFS HCI version
@@ -332,6 +333,7 @@ struct ufs_pwr_mode_info {
  */
 struct ufs_hba_variant_ops {
 	const char *name;
+	int	max_num_rtt;
 	int	(*init)(struct ufs_hba *);
 	void    (*exit)(struct ufs_hba *);
 	u32	(*get_ufs_hci_version)(struct ufs_hba *);