[PATCH v3 08/10] VAS: Define vas_win_close() interface

[Sukadev Bhattiprolu]

Define the vas_win_close() interface which should be used to close a
send or receive windows.

While the hardware configurations required to open send and receive windows
differ, the configuration to close a window is the same for both. So we use
a single interface to close the window.

Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
---
Changelog[v3]:
	- Fix order of parameters in GET_FIELD().
	- Update references and sequence for closing/quiescing a window.
---
 arch/powerpc/include/asm/vas.h |   7 +++
 drivers/misc/vas/vas-window.c  | 120 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 127 insertions(+)

diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h
index d49b05b..fc00249 100644
--- a/arch/powerpc/include/asm/vas.h
+++ b/arch/powerpc/include/asm/vas.h
@@ -83,6 +83,13 @@ extern struct vas_window *vas_rx_win_open(int vasid, enum vas_cop_type cop,
 			struct vas_rx_win_attr *attr);
 
 /*
+ * Close the send or receive window identified by @win. For receive windows
+ * return -EAGAIN if there are active send windows attached to this receive
+ * window.
+ */
+int vas_win_close(struct vas_window *win);
+
+/*
  * Get/Set bit fields
  */
 #define GET_FIELD(m, v)		(((v) & (m)) >> MASK_LSH(m))
diff --git a/drivers/misc/vas/vas-window.c b/drivers/misc/vas/vas-window.c
index 605a2fa..40e4f7d 100644
--- a/drivers/misc/vas/vas-window.c
+++ b/drivers/misc/vas/vas-window.c
@@ -548,6 +548,14 @@ int vas_window_reset(struct vas_instance *vinst, int winid)
 	return 0;
 }
 
+static void put_rx_win(struct vas_window *rxwin)
+{
+	/* Better not be a send window! */
+	WARN_ON_ONCE(rxwin->tx_win);
+
+	atomic_dec(&rxwin->num_txwins);
+}
+
 struct vas_window *get_vinstance_rxwin(struct vas_instance *vinst,
 			enum vas_cop_type cop)
 {
@@ -747,3 +755,115 @@ struct vas_window *vas_rx_win_open(int vasid, enum vas_cop_type cop,
 	vas_release_window_id(&vinst->ida, rxwin->winid);
 	return ERR_PTR(rc);
 }
+
+static void poll_window_busy_state(struct vas_window *window)
+{
+	int busy;
+	uint64_t val;
+
+retry:
+	/*
+	 * Poll Window Busy flag
+	 */
+	val = read_hvwc_reg(window, VREG(WIN_STATUS));
+	busy = GET_FIELD(VAS_WIN_BUSY, val);
+	if (busy) {
+		val = 0;
+		schedule_timeout(2000);
+		goto retry;
+	}
+}
+
+static void poll_window_credits_return(struct vas_window *window)
+{
+	int credits;
+	uint64_t val;
+
+retry:
+	/*
+	 * Poll Window Credits
+	 */
+	if (window->tx_win) {
+		val = read_hvwc_reg(window, VREG(TX_WCRED));
+		credits = GET_FIELD(VAS_TX_WCRED, val);
+	} else {
+		val = read_hvwc_reg(window, VREG(LRX_WCRED));
+		credits = GET_FIELD(VAS_LRX_WCRED, val);
+	}
+
+	if (credits != VAS_WCREDS_DEFAULT) {
+		val = 0;
+		schedule_timeout(2000);
+		goto retry;
+	}
+}
+
+static void poll_window_castout(struct vas_window *window)
+{
+	int cached;
+	uint64_t val;
+
+	/* Cast window context out of the cache */
+retry:
+	val = read_hvwc_reg(window, VREG(WIN_CTX_CACHING_CTL));
+	cached = GET_FIELD(VAS_WIN_CACHE_STATUS, val);
+	if (cached) {
+		val = 0ULL;
+		val = SET_FIELD(VAS_CASTOUT_REQ, val, 1);
+		val = SET_FIELD(VAS_PUSH_TO_MEM, val, 0);
+		write_hvwc_reg(window, VREG(WIN_CTX_CACHING_CTL), val);
+
+		schedule_timeout(2000);
+		goto retry;
+	}
+}
+
+/*
+ * Close a window.
+ *
+ * See Section 1.12.1 of VAS workbook v1.05 for details on closing window:
+ *	- disable new paste operations (unmap paste address)
+ *	- Poll for the "Window Busy" bit to be cleared
+ *	- Clear the Open/Enable bit for the Window.
+ *	- Poll for return of window Credits (implies FIFO empty for Rx win?)
+ *	- Unpin and cast window context out of cache
+ *
+ * Besides the hardware, kernel has some bookkeeping of course.
+ */
+int vas_win_close(struct vas_window *window)
+{
+	uint64_t val;
+
+	if (!window)
+		return 0;
+
+	if (!window->tx_win && atomic_read(&window->num_txwins) != 0) {
+		pr_devel("VAS: Attempting to close an active Rx window!\n");
+		WARN_ON_ONCE(1);
+		return -EAGAIN;
+	}
+
+	unmap_wc_paste_kaddr(window);
+
+	poll_window_busy_state(window);
+
+	/* Unpin window from cache and close it */
+	val = read_hvwc_reg(window, VREG(WINCTL));
+	val = SET_FIELD(VAS_WINCTL_PIN, val, 0);
+	val = SET_FIELD(VAS_WINCTL_OPEN, val, 0);
+	write_hvwc_reg(window, VREG(WINCTL), val);
+
+	poll_window_credits_return(window);
+
+	poll_window_castout(window);
+
+	/* if send window, drop reference to matching receive window */
+	if (window->tx_win)
+		put_rx_win(window->rxwin);
+
+	vas_release_window_id(&window->vinst->ida, window->winid);
+
+	vas_window_free(window);
+
+	return 0;
+}
-- 
2.7.4