[PATCH v4 09/11] VAS: Define vas_win_close() interface

Sukadev Bhattiprolu
2017-03-31T05:15:02Z

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@linux.vnet.ibm.com>
---
Changelog[v4]:
- Drop the poll for credits return (we can set the required credit,
but cannot really find the available credit at a point in time)

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 +++
arch/powerpc/platforms/powernv/vas-window.c | 96 +++++++++++++++++++++++++++--
2 files changed, 99 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h
index 09ea6f7..c923b8f 100644
--- a/arch/powerpc/include/asm/vas.h
+++ b/arch/powerpc/include/asm/vas.h
@@ -76,4 +76,11 @@ extern void vas_init_rx_win_attr(struct vas_rx_win_attr *rxattr,
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);
+
#endif /* _MISC_VAS_H */
diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
index 04f6bb2..7b1a36c 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -470,7 +470,7 @@ int vas_assign_window_id(struct ida *ida)
return winid;
}

-void vas_window_free(struct vas_window *window)
+static void vas_window_free(struct vas_window *window)
{
unmap_wc_mmio_bars(window);
kfree(window->paste_addr_name);
@@ -498,10 +498,12 @@ static struct vas_window *vas_window_alloc(struct vas_instance *vinst, int id)
return NULL;
}

-/* stub for now */
-int vas_win_close(struct vas_window *window)
+static void put_rx_win(struct vas_window *rxwin)
{
- return -1;
+ /* 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,
@@ -706,3 +708,89 @@ 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_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_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