[PATCH v2] mmc: sdhci-msm: Add sdhci_reset() implementation

[Georgi Djakov <georgi.djakov@linaro.org>]

On apq8016, apq8084 and apq8074 platforms, writing to the software
reset register triggers the "power irq". We need to ack and handle
the irq, otherwise the following message appears:

mmc0: Reset 0x1 never completed.
sdhci: =========== REGISTER DUMP (mmc0)===========
sdhci: Sys addr: 0x00000000 | Version:  0x00002e02
sdhci: Blk size: 0x00004000 | Blk cnt:  0x00000000
sdhci: Argument: 0x00000000 | Trn mode: 0x00000000
sdhci: Present:  0x01f80000 | Host ctl: 0x00000000
sdhci: Power:    0x00000000 | Blk gap:  0x00000000
sdhci: Wake-up:  0x00000000 | Clock:    0x00000003
sdhci: Timeout:  0x00000000 | Int stat: 0x00000000
sdhci: Int enab: 0x00000000 | Sig enab: 0x00000000
sdhci: AC12 err: 0x00000000 | Slot int: 0x00000000
sdhci: Caps:     0x322dc8b2 | Caps_1:   0x00008007
sdhci: Cmd:      0x00000000 | Max curr: 0x00000000
sdhci: Host ctl2: 0x00000000
sdhci: ADMA Err: 0x00000000 | ADMA Ptr: 0x0000000000000000
sdhci: ===========================================

Fix it by implementing the custom sdhci_reset() function,
which performs the software reset and then handles the irq.

Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
---

Changes since v1: (https://lkml.org/lkml/2016/11/22/411)
 * Perform the software reset by just writing to the SDHCI_SOFTWARE_RESET
   register and then check for the irq.

 drivers/mmc/host/sdhci-msm.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index 32879b845b75..157ae07f9309 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -1019,6 +1019,33 @@ static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
 	__sdhci_msm_set_clock(host, clock);
 }
 
+void sdhci_msm_reset(struct sdhci_host *host, u8 mask)
+{
+	unsigned long timeout = 100;
+
+	sdhci_writeb(host, mask, SDHCI_SOFTWARE_RESET);
+
+	if (mask & SDHCI_RESET_ALL) {
+		host->clock = 0;
+
+		/*
+		 * SDHCI_RESET_ALL triggers the PWR IRQ and we need
+		 * to handle it here.
+		 */
+		sdhci_msm_voltage_switch(host);
+	}
+
+	while (sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask) {
+		if (timeout == 0) {
+			pr_err("%s: Reset 0x%x never completed.\n",
+			       mmc_hostname(host->mmc), (int)mask);
+			return;
+		}
+		timeout--;
+		mdelay(1);
+	}
+}
+
 static const struct of_device_id sdhci_msm_dt_match[] = {
 	{ .compatible = "qcom,sdhci-msm-v4" },
 	{},
@@ -1028,7 +1055,7 @@ MODULE_DEVICE_TABLE(of, sdhci_msm_dt_match);
 
 static const struct sdhci_ops sdhci_msm_ops = {
 	.platform_execute_tuning = sdhci_msm_execute_tuning,
-	.reset = sdhci_reset,
+	.reset = sdhci_msm_reset,
 	.set_clock = sdhci_msm_set_clock,
 	.get_min_clock = sdhci_msm_get_min_clock,
 	.get_max_clock = sdhci_msm_get_max_clock,