Factor out the common code into a new exynos_ufs_shareability() function
and provide a dedicated gs101_drv_init() hook.

This allows us to enable WriteBooster capability (UFSHCD_CAP_WB_EN) in a
way that doesn't effect other SoCs supported in this driver.

WriteBooster improves write speeds by enabling a pseudo SLC cache. Using
the `fio seqwrite` test we can achieve speeds of 945MB/s with this feature
enabled (until the cache is exhausted) before dropping back to ~260MB/s
(which are the speeds we see without the WriteBooster feature enabled).

Assuming the UFSHCD_CAP_WB_EN capability is set by the host then
WriteBooster can also be enabled and disabled via sysfs so it is possible
for the system to only enable it when extra write performance is required.

Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
---
v3: update to new drv_init() protoype
---
 drivers/ufs/host/ufs-exynos.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/ufs/host/ufs-exynos.c b/drivers/ufs/host/ufs-exynos.c
index 378c16d905c1..d59e1933b64e 100644
--- a/drivers/ufs/host/ufs-exynos.c
+++ b/drivers/ufs/host/ufs-exynos.c
@@ -198,7 +198,7 @@ static inline void exynos_ufs_ungate_clks(struct exynos_ufs *ufs)
 	exynos_ufs_ctrl_clkstop(ufs, false);
 }
 
-static int exynosauto_ufs_drv_init(struct exynos_ufs *ufs)
+static int exynos_ufs_shareability(struct exynos_ufs *ufs)
 {
 	/* IO Coherency setting */
 	if (ufs->sysreg) {
@@ -210,6 +210,21 @@ static int exynosauto_ufs_drv_init(struct exynos_ufs *ufs)
 	return 0;
 }
 
+static int gs101_ufs_drv_init(struct exynos_ufs *ufs)
+{
+	struct ufs_hba *hba = ufs->hba;
+
+	/* Enable WriteBooster */
+	hba->caps |= UFSHCD_CAP_WB_EN;
+
+	return exynos_ufs_shareability(ufs);
+}
+
+static int exynosauto_ufs_drv_init(struct exynos_ufs *ufs)
+{
+	return exynos_ufs_shareability(ufs);
+}
+
 static int exynosauto_ufs_post_hce_enable(struct exynos_ufs *ufs)
 {
 	struct ufs_hba *hba = ufs->hba;
@@ -2120,7 +2135,7 @@ static const struct exynos_ufs_drv_data gs101_ufs_drvs = {
 	.opts			= EXYNOS_UFS_OPT_SKIP_CONFIG_PHY_ATTR |
 				  EXYNOS_UFS_OPT_UFSPR_SECURE |
 				  EXYNOS_UFS_OPT_TIMER_TICK_SELECT,
-	.drv_init		= exynosauto_ufs_drv_init,
+	.drv_init		= gs101_ufs_drv_init,
 	.pre_link		= gs101_ufs_pre_link,
 	.post_link		= gs101_ufs_post_link,
 	.pre_pwr_change		= gs101_ufs_pre_pwr_change,
-- 
2.47.0.163.g1226f6d8fa-goog