brcmfmac: sdio: shorten retry loop in brcmf_sdio_kso_control()

In brcmf_sdio_kso_control() there is a retry loop as hardware may take
time to settle. However, when the call to brcmf_sdiod_regrb() returns
an error it is due to SDIO access failure and it makes no sense to wait
for hardware to settle. This patch aborts the loop after a number of
subsequent access errors.
Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c

@@ -313,6 +313,7 @@ struct rte_console {
 
 #define KSO_WAIT_US 50
 #define MAX_KSO_ATTEMPTS (PMU_MAX_TRANSITION_DLY/KSO_WAIT_US)
+#define BRCMF_SDIO_MAX_ACCESS_ERRORS	5
 
 /*
  * Conversion of 802.1D priority to precedence level
@@ -677,6 +678,7 @@ brcmf_sdio_kso_control(struct brcmf_sdio *bus, bool on)
 {
 	u8 wr_val = 0, rd_val, cmp_val, bmask;
 	int err = 0;
+	int err_cnt = 0;
 	int try_cnt = 0;
 
 	brcmf_dbg(TRACE, "Enter: on=%d\n", on);
@@ -712,9 +714,14 @@ brcmf_sdio_kso_control(struct brcmf_sdio *bus, bool on)
 		 */
 		rd_val = brcmf_sdiod_regrb(bus->sdiodev, SBSDIO_FUNC1_SLEEPCSR,
 					   &err);
-		if (((rd_val & bmask) == cmp_val) && !err)
+		if (!err) {
+			if ((rd_val & bmask) == cmp_val)
+				break;
+			err_cnt = 0;
+		}
+		/* bail out upon subsequent access errors */
+		if (err && (err_cnt++ > BRCMF_SDIO_MAX_ACCESS_ERRORS))
 			break;
-
 		udelay(KSO_WAIT_US);
 		brcmf_sdiod_regwb(bus->sdiodev, SBSDIO_FUNC1_SLEEPCSR,
 				  wr_val, &err);