From 6fccac16c578c699bf0714a6c930b0ceb81305a0 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu Date: Tue, 7 Nov 2017 18:23:48 -0800 Subject: [PATCH] powerpc/vas: poll for return of window credits Normally, the NX driver waits for the CRBs to be processed before closing the window. But it is better to ensure that the credits are returned before the window gets reassigned later. Signed-off-by: Sukadev Bhattiprolu Signed-off-by: Michael Ellerman --- arch/powerpc/platforms/powernv/vas-window.c | 45 +++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c index a59a187c0cd1..23c13a7dcf89 100644 --- a/arch/powerpc/platforms/powernv/vas-window.c +++ b/arch/powerpc/platforms/powernv/vas-window.c @@ -1062,6 +1062,49 @@ int vas_paste_crb(struct vas_window *txwin, int offset, bool re) } EXPORT_SYMBOL_GPL(vas_paste_crb); +/* + * If credit checking is enabled for this window, poll for the return + * of window credits (i.e for NX engines to process any outstanding CRBs). + * Since NX-842 waits for the CRBs to be processed before closing the + * window, we should not have to wait for too long. + * + * TODO: We retry in 10ms intervals now. We could/should probably peek at + * the VAS_LRFIFO_PUSH_OFFSET register to get an estimate of pending + * CRBs on the FIFO and compute the delay dynamically on each retry. + * But that is not really needed until we support NX-GZIP access from + * user space. (NX-842 driver waits for CSB and Fast thread-wakeup + * doesn't use credit checking). + */ +static void poll_window_credits(struct vas_window *window) +{ + u64 val; + int creds, mode; + + val = read_hvwc_reg(window, VREG(WINCTL)); + if (window->tx_win) + mode = GET_FIELD(VAS_WINCTL_TX_WCRED_MODE, val); + else + mode = GET_FIELD(VAS_WINCTL_RX_WCRED_MODE, val); + + if (!mode) + return; +retry: + if (window->tx_win) { + val = read_hvwc_reg(window, VREG(TX_WCRED)); + creds = GET_FIELD(VAS_TX_WCRED, val); + } else { + val = read_hvwc_reg(window, VREG(LRX_WCRED)); + creds = GET_FIELD(VAS_LRX_WCRED, val); + } + + if (creds < window->wcreds_max) { + val = 0; + set_current_state(TASK_UNINTERRUPTIBLE); + schedule_timeout(msecs_to_jiffies(10)); + goto retry; + } +} + /* * Wait for the window to go to "not-busy" state. It should only take a * short time to queue a CRB, so window should not be busy for too long. @@ -1149,6 +1192,8 @@ int vas_win_close(struct vas_window *window) unpin_close_window(window); + poll_window_credits(window); + poll_window_castout(window); /* if send window, drop reference to matching receive window */