mmc: tmio: fix a deadlock

Currently the tmio-mmc driver contains a recursive runtime PM method
invocation, which leads to a deadlock on a mutex. Avoid it by taking
care not to request DMA too early.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/tmio_mmc.h

@@ -109,6 +109,7 @@ static inline void tmio_mmc_kunmap_atomic(struct scatterlist *sg,
 
 #if defined(CONFIG_MMC_SDHI) || defined(CONFIG_MMC_SDHI_MODULE)
 void tmio_mmc_start_dma(struct tmio_mmc_host *host, struct mmc_data *data);
+void tmio_mmc_enable_dma(struct tmio_mmc_host *host, bool enable);
 void tmio_mmc_request_dma(struct tmio_mmc_host *host, struct tmio_mmc_data *pdata);
 void tmio_mmc_release_dma(struct tmio_mmc_host *host);
 #else
@@ -117,6 +118,10 @@ static inline void tmio_mmc_start_dma(struct tmio_mmc_host *host,
 {
 }
 
+static inline void tmio_mmc_enable_dma(struct tmio_mmc_host *host, bool enable)
+{
+}
+
 static inline void tmio_mmc_request_dma(struct tmio_mmc_host *host,
 				 struct tmio_mmc_data *pdata)
 {

drivers/mmc/host/tmio_mmc_dma.c

@@ -22,8 +22,11 @@
 
 #define TMIO_MMC_MIN_DMA_LEN 8
 
-static void tmio_mmc_enable_dma(struct tmio_mmc_host *host, bool enable)
+void tmio_mmc_enable_dma(struct tmio_mmc_host *host, bool enable)
 {
+	if (!host->chan_tx || !host->chan_rx)
+		return;
+
 #if defined(CONFIG_SUPERH) || defined(CONFIG_ARCH_SHMOBILE)
 	/* Switch DMA mode on or off - SuperH specific? */
 	sd_ctrl_write16(host, CTL_DMA_ENABLE, enable ? 2 : 0);

drivers/mmc/host/tmio_mmc_pio.c

@@ -984,7 +984,7 @@ int tmio_mmc_host_resume(struct device *dev)
 	if (host->pm_global) {
 		/* Runtime PM resume callback didn't run */
 		tmio_mmc_reset(host);
-		tmio_mmc_request_dma(host, host->pdata);
+		tmio_mmc_enable_dma(host, true);
 		host->pm_global = false;
 	}
 
@@ -1007,7 +1007,7 @@ int tmio_mmc_host_runtime_resume(struct device *dev)
 	struct tmio_mmc_data *pdata = host->pdata;
 
 	tmio_mmc_reset(host);
-	tmio_mmc_request_dma(host, host->pdata);
+	tmio_mmc_enable_dma(host, true);
 
 	if (pdata->power) {
 		/* Only entered after a card-insert interrupt */