Date:	Wed, 3 Feb 2016 11:41:40 -0500
From:	Murali Karicheri <m-karicheri2@...com>
To:	Arnd Bergmann <arnd@...db.de>,
	Grygorii Strashko <grygorii.strashko@...com>
CC:	"Franklin S Cooper Jr." <fcooper@...com>, <netdev@...r.kernel.org>,
	<w-kwok2@...com>, <davem@...emloft.net>
Subject: Re: Keystone 2 boards boot failure

On 02/03/2016 11:20 AM, Arnd Bergmann wrote:
> 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.
Arnd,

Why do think so? I see in arch/arm/boot/dts/keystone.dtsi

        soc {
                #address-cells = <1>;
                #size-cells = <1>;
                compatible = "ti,keystone","simple-bus";
                interrupt-parent = <&gic>;
                ranges = <0x0 0x0 0x0 0xc0000000>;
                dma-ranges = <0x80000000 0x8 0x00000000 0x80000000>;

AFAIK, On Keystone, dma address is 32 bit and Physical DDR address is
64 bit (actually 36 bit, LPAE address). The conversion happens based on
pfn_offset which is calculated based on the above dma-range property.

> 
> 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.
> 

Not sure why? Keystone is that platform where they are 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;
> 
> 


-- 
Murali Karicheri
Linux Kernel, Keystone

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