[PATCH 09/10] staging: wfx: ensure HIF request has been sent before polling

Jerome Pouiller
2022-02-25T11:25:27Z

From: Jérôme Pouiller <jerome.pouiller@silabs.com>

wfx_bh_request_tx() send HIF request asynchronously through bh_work().
Then the caller will run wfx_bh_poll_irq() to poll the answer.

However it useless to burn CPU cycles for the polling while the request
has yet been sent. Worse, wfx_bh_poll_irq() may get the CPU and prevent
wfx_bh_request_tx() to run. This problem has been observed on mono core
architecture.

This first exchange is correct:
kworker/u2:1-24 [000] .... : io_read32: CONTROL: 00003000
kworker/u2:1-24 [000] .... : io_read32: CONTROL: 00003000
kworker/u2:1-24 [000] .... : io_read32: CONTROL: 00003004
kworker/u2:1-24 [000] .... : io_read32: CONTROL: 00003004
kworker/0:1H-40 [000] .... : io_read: QUEUE: 08 00 09 0c 00 00 00 00 3a 7b 00 30 (12 bytes)
kworker/0:1H-40 [000] .... : piggyback: CONTROL: 00003000
kworker/0:1H-40 [000] .... : hif_recv: 0:2:CNF_CONFIGURATION: 00 00 00 00 (8 bytes)
kworker/0:1H-40 [000] .... : io_read32: CONFIG: 03010200
kworker/0:1H-40 [000] .... : bh_stats: IND/REQ/CNF: 0/ 0/ 1, REQ in progress: 0, WUP: release

... while the following is not:
kworker/u2:1-24 [000] .... : io_read32: CONTROL: 00003000
kworker/u2:1-24 [000] .... : io_read32: CONTROL: 00003000
kworker/u2:1-24 [000] .... : io_read32: CONTROL: 00003000
[...loop until timeout...]
wfx-sdio mmc0:0001:1: time out while polling control register

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
---
drivers/staging/wfx/bh.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/drivers/staging/wfx/bh.c b/drivers/staging/wfx/bh.c
index 4c6ba9c342a6..bcea9d5b119c 100644
--- a/drivers/staging/wfx/bh.c
+++ b/drivers/staging/wfx/bh.c
@@ -295,6 +295,7 @@ void wfx_bh_poll_irq(struct wfx_dev *wdev)
u32 reg;

WARN(!wdev->poll_irq, "unexpected IRQ polling can mask IRQ");
+ flush_workqueue(system_highpri_wq);
start = ktime_get();
for (;;) {
wfx_control_reg_read(wdev, &reg);
--
2.34.1