Date:	Wed, 03 Feb 2016 17:20:13 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	"Franklin S Cooper Jr." <fcooper@...com>, m-karicheri2@...com,
	netdev@...r.kernel.org, w-kwok2@...com, davem@...emloft.net
Subject: Re: Keystone 2 boards boot failure

On Wednesday 03 February 2016 16:21:05 Grygorii Strashko wrote:
> On 02/03/2016 04:11 PM, Franklin S Cooper Jr. wrote:
> > On 02/02/2016 07:19 PM, Franklin S Cooper Jr. wrote:
> >>>
> >> So only making this change on the latest master with no
> >> other changes I see the boot problem again.
> 
> yep. I can confirm that.
> 
> Also, I'm today came up with the similar fix that you've proposed before in this thread.
> So, Could we move forward this way?

I still think it would be good to actually understand what the actual
problem was.

> From 8280895f01b33edba303e7374431bef47630f26c Mon Sep 17 00:00:00 2001
> From: Grygorii Strashko <grygorii.strashko@...com>
> Date: Wed, 3 Feb 2016 15:11:40 +0200
> Subject: [PATCH] net: ti: netcp: restore get/set_pad_info() functionality
> 
> The commit 899077791403 ("netcp: try to reduce type confusion in descriptors")
> introduces a regression in Kernel 4.5-rc1 as it breaks
> get/set_pad_info() functionality.
> 
> The TI NETCP driver uses pad0 and pad1 fields of knav_dma_desc to
> store DMA/MEM buffer pointer and buffer size respectively. And in both
> cases the pointer type size is 32 bit regardless of LAPE enabled or
> not.
> 			!LAPE	LPAE
> sizeof(void*)		32bit	32bit
> sizeof(dma_addr_t) 	32bit	32bit
> sizeof(phys_addr_t) 	32bit	64bit
> 

This looks wrong: I was getting the build warnings originally
because of 64-bit dma_addr_t, and that should be the only way that
this driver can operate, because in some configurations on keystone
there is no memory below 4GB, and there is no dma-ranges property
in the DT that shifts around the start of the DMA addresses.

This doesn't all fit together yet, maybe you have a better idea
of what is going on.

I don't think we should ever have a platform that has dma_addr_t
and phys_addr_t be different.

> Unfortunately, above commit changed buffer's pointers save/restore
> code (get/set_pad_info()) and added intermediate conversation to u64
> which causes TI NETCP driver crash in RX/TX path due to "Unable to
> handle kernel NULL pointer" exception.

The conversion is not what made it crash, it must be a bug in the
conversion ;-)

> @@ -163,11 +153,10 @@ static void set_desc_info(u32 desc_info, u32 pkt_info,
>  	desc->packet_info = cpu_to_le32(pkt_info);
>  }
>  
> -static void set_pad_info(u32 pad0, u32 pad1, u32 pad2, struct knav_dma_desc *desc)
> +static void set_pad_info(u32 pad0, u32 pad1, struct knav_dma_desc *desc)
>  {
>  	desc->pad[0] = cpu_to_le32(pad0);
>  	desc->pad[1] = cpu_to_le32(pad1);
> -	desc->pad[2] = cpu_to_le32(pad1);
>  }

As in my earlier patch, the line you are removing here was clearly
broken, but evidently that is not the only bug.

>  static void set_org_pkt_info(dma_addr_t buff, u32 buff_len,
> @@ -581,7 +570,6 @@ static void netcp_free_rx_desc_chain(struct netcp_intf *netcp,
>  	dma_addr_t dma_desc, dma_buf;
>  	unsigned int buf_len, dma_sz = sizeof(*ndesc);
>  	void *buf_ptr;
> -	u32 pad[2];
>  	u32 tmp;
>  
>  	get_words(&dma_desc, 1, &desc->next_desc);
> @@ -593,14 +581,12 @@ static void netcp_free_rx_desc_chain(struct netcp_intf *netcp,
>  			break;
>  		}
>  		get_pkt_info(&dma_buf, &tmp, &dma_desc, ndesc);
> -		get_pad_ptr(&buf_ptr, ndesc);
> +		get_pad_info((u32 *)&buf_ptr, &buf_len, ndesc);

I'd prefer not to put code like this back, as this cannot possibly
do the right thing on a 64-bit architecture.


> @@ -1078,7 +1058,6 @@ netcp_tx_map_skb(struct sk_buff *skb, struct netcp_intf *netcp)
>  		u32 page_offset = frag->page_offset;
>  		u32 buf_len = skb_frag_size(frag);
>  		dma_addr_t desc_dma;
> -		u32 desc_dma_32;
>  		u32 pkt_info;
>  
>  		dma_addr = dma_map_page(dev, page, page_offset, buf_len,
> @@ -1100,8 +1079,7 @@ netcp_tx_map_skb(struct sk_buff *skb, struct netcp_intf *netcp)
>  			(netcp->tx_compl_qid & KNAV_DMA_DESC_RETQ_MASK) <<
>  				KNAV_DMA_DESC_RETQ_SHIFT;
>  		set_pkt_info(dma_addr, buf_len, 0, ndesc);
> -		desc_dma_32 = (u32)desc_dma;
> -		set_words(&desc_dma_32, 1, &pdesc->next_desc);
> +		set_words(&desc_dma, 1, &pdesc->next_desc);
>  		pkt_len += buf_len;
>  		if (pdesc != desc)
>  			knav_pool_desc_map(netcp->tx_pool, pdesc,

This is clearly broken on big-endian kernels with 64-bit dma_addr_t, so even
if we revert the rest I think this part has to stay.

I have another version for testing below. That removes the logic that
splits and reassembles the 64-bit values, but leaves the other changes
in place. Can you try this?

	Arnd


diff --git a/drivers/net/ethernet/ti/netcp_core.c b/drivers/net/ethernet/ti/netcp_core.c
index c61d66d38634..cda19f2401c1 100644
--- a/drivers/net/ethernet/ti/netcp_core.c
+++ b/drivers/net/ethernet/ti/netcp_core.c
@@ -120,16 +120,14 @@ static void get_pkt_info(dma_addr_t *buff, u32 *buff_len, dma_addr_t *ndesc,
 static void get_pad_info(u32 *pad0, u32 *pad1, u32 *pad2, struct knav_dma_desc *desc)
 {
 	*pad0 = le32_to_cpu(desc->pad[0]);
-	*pad1 = le32_to_cpu(desc->pad[1]);
-	*pad2 = le32_to_cpu(desc->pad[2]);
+	*pad2 = le32_to_cpu(desc->pad[1]);
 }
 
 static void get_pad_ptr(void **padptr, struct knav_dma_desc *desc)
 {
 	u64 pad64;
 
-	pad64 = le32_to_cpu(desc->pad[0]) +
-		((u64)le32_to_cpu(desc->pad[1]) << 32);
+	pad64 = le32_to_cpu(desc->pad[0]);
 	*padptr = (void *)(uintptr_t)pad64;
 }
 
@@ -166,8 +164,7 @@ static void set_desc_info(u32 desc_info, u32 pkt_info,
 static void set_pad_info(u32 pad0, u32 pad1, u32 pad2, struct knav_dma_desc *desc)
 {
 	desc->pad[0] = cpu_to_le32(pad0);
-	desc->pad[1] = cpu_to_le32(pad1);
-	desc->pad[2] = cpu_to_le32(pad1);
+	desc->pad[1] = cpu_to_le32(pad2);
 }
 
 static void set_org_pkt_info(dma_addr_t buff, u32 buff_len,
@@ -581,7 +578,7 @@ static void netcp_free_rx_desc_chain(struct netcp_intf *netcp,
 	dma_addr_t dma_desc, dma_buf;
 	unsigned int buf_len, dma_sz = sizeof(*ndesc);
 	void *buf_ptr;
-	u32 pad[2];
+	u32 pad;
 	u32 tmp;
 
 	get_words(&dma_desc, 1, &desc->next_desc);
@@ -599,8 +596,8 @@ static void netcp_free_rx_desc_chain(struct netcp_intf *netcp,
 		knav_pool_desc_put(netcp->rx_pool, desc);
 	}
 
-	get_pad_info(&pad[0], &pad[1], &buf_len, desc);
-	buf_ptr = (void *)(uintptr_t)(pad[0] + ((u64)pad[1] << 32));
+	get_pad_info(&pad, NULL, &buf_len, desc);
+	buf_ptr = (void *)(uintptr_t)(pad);
 
 	if (buf_ptr)
 		netcp_frag_free(buf_len <= PAGE_SIZE, buf_ptr);
@@ -653,8 +650,8 @@ static int netcp_process_one_rx_packet(struct netcp_intf *netcp)
 	}
 
 	get_pkt_info(&dma_buff, &buf_len, &dma_desc, desc);
-	get_pad_info(&pad[0], &pad[1], &org_buf_len, desc);
-	org_buf_ptr = (void *)(uintptr_t)(pad[0] + ((u64)pad[1] << 32));
+	get_pad_info(&pad[0], NULL, &org_buf_len, desc);
+	org_buf_ptr = (void *)(uintptr_t)(pad[0]);
 
 	if (unlikely(!org_buf_ptr)) {
 		dev_err(netcp->ndev_dev, "NULL bufptr in desc\n");
@@ -858,8 +855,7 @@ static int netcp_allocate_rx_buf(struct netcp_intf *netcp, int fdq)
 		if (unlikely(dma_mapping_error(netcp->dev, dma)))
 			goto fail;
 
-		pad[0] = lower_32_bits((uintptr_t)bufptr);
-		pad[1] = upper_32_bits((uintptr_t)bufptr);
+		pad[0] = (uintptr_t)bufptr;
 
 	} else {
 		/* Allocate a secondary receive queue entry */
@@ -870,8 +866,7 @@ static int netcp_allocate_rx_buf(struct netcp_intf *netcp, int fdq)
 		}
 		buf_len = PAGE_SIZE;
 		dma = dma_map_page(netcp->dev, page, 0, buf_len, DMA_TO_DEVICE);
-		pad[0] = lower_32_bits(dma);
-		pad[1] = upper_32_bits(dma);
+		pad[0] = (u32)(dma);
 		pad[2] = 0;
 	}
 
@@ -882,7 +877,7 @@ static int netcp_allocate_rx_buf(struct netcp_intf *netcp, int fdq)
 	pkt_info |= (netcp->rx_queue_id & KNAV_DMA_DESC_RETQ_MASK) <<
 		    KNAV_DMA_DESC_RETQ_SHIFT;
 	set_org_pkt_info(dma, buf_len, hwdesc);
-	set_pad_info(pad[0], pad[1], pad[2], hwdesc);
+	set_pad_info(pad[0], 0, pad[2], hwdesc);
 	set_desc_info(desc_info, pkt_info, hwdesc);
 
 	/* Push to FDQs */
@@ -1194,10 +1189,8 @@ static int netcp_tx_submit_skb(struct netcp_intf *netcp,
 	}
 
 	set_words(&tmp, 1, &desc->packet_info);
-	tmp = lower_32_bits((uintptr_t)&skb);
+	tmp = (uintptr_t)&skb;
 	set_words(&tmp, 1, &desc->pad[0]);
-	tmp = upper_32_bits((uintptr_t)&skb);
-	set_words(&tmp, 1, &desc->pad[1]);
 
 	if (tx_pipe->flags & SWITCH_TO_PORT_IN_TAGINFO) {
 		tmp = tx_pipe->switch_to_port;

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