Patch "mmc: dw_mmc: fix falling from idmac to PIO mode when dw_mci_reset occurs" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

mmc: dw_mmc: fix falling from idmac to PIO mode when dw_mci_reset occurs

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mmc-dw_mmc-fix-falling-from-idmac-to-pio-mode-when-dw_mci_reset-occurs.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Evgeniy Didin <[email protected]>
Date: Wed, 14 Mar 2018 22:30:51 +0300
Subject: mmc: dw_mmc: fix falling from idmac to PIO mode when dw_mci_reset occurs

From: Evgeniy Didin <[email protected]>

commit 47b7de2f6c18f75d1f2716efe752cba43f32a626 upstream.

It was found that in IDMAC mode after soft-reset driver switches to PIO mode.

That's what happens in case of DTO timeout overflow calculation failure:
1. soft-reset is called
2. driver restarts dma
3. descriptors states are checked, one of descriptor is owned by the IDMAC.
4. driver can't use DMA and then switches to PIO mode.

Failure was already fixed in:
https://www.spinics.net/lists/linux-mmc/msg48125.html.

Behaviour while soft-reset is not something we except or even want to happen. So we switch from dw_mci_idmac_reset to dw_mci_idmac_init, so descriptors are cleaned before starting dma.

And while at it explicitly zero des0 which otherwise might contain garbage as being allocated by dmam_alloc_coherent().

---
 drivers/mmc/host/dw_mmc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

@@ -619,6 +619,7 @@ static int dw_mci_idmac_init(struct dw_m
 					(sizeof(struct idmac_desc_64addr) *
 							(i + 1))) >> 32;
 			/* Initialize reserved and buffer size fields to "0" */
+			p->des0 = 0;
 			p->des1 = 0;
 			p->des2 = 0;
 			p->des3 = 0;

@@ -640,6 +641,7 @@ static int dw_mci_idmac_init(struct dw_m
 		     i++, p++) {
 			p->des3 = cpu_to_le32(host->sg_dma +
 					(sizeof(struct idmac_desc) * (i + 1)));
+			p->des0 = 0;
 			p->des1 = 0;
 		}
 

@@ -2807,8 +2809,8 @@ static bool dw_mci_reset(struct dw_mci *
 	}
 
 	if (host->use_dma == TRANS_MODE_IDMAC)
-		/* It is also recommended that we reset and reprogram idmac */
-		dw_mci_idmac_reset(host);
+		/* It is also required that we reinit idmac */
+		dw_mci_idmac_init(host);
 
 	ret = true;
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/mmc-dw_mmc-fix-falling-from-idmac-to-pio-mode-when-dw_mci_reset-occurs.patch