Subject: Re: Keystone 2 boards boot failure

From: Murali Karicheri <[email-masked]>
Date: Wed, 3 Feb 2016 11:45:35 -0500

On 02/03/2016 11:31 AM, Grygorii Strashko wrote:
> On 02/03/2016 06:20 PM, 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 <[email-masked]>
>>> 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.
> 
> see 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>;
>         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> config:
> 
> CONFIG_ARCH_PHYS_ADDR_T_64BIT=y
> CONFIG_PHYS_ADDR_T_64BIT=y
> 
> and
> 
> #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT <--- should not be defined for KS2
> typedef u64 dma_addr_t;
> #else
> typedef u32 dma_addr_t;
> #endif
> 
> Above is valid configuration for Keystone 2 with LPAE=y
> 
>>
>> 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.
> 
> This is a valid case.
> 
>>
>>> 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.
> 
> Keystone 2 has 32-bit dma_addr_t
> 
>>
>> 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?
> 
> Sry, but we really don't need this logic for KS2 ;)
> 
Just replied as well in my response.

Yes Agree. Currently we don't have a use case for Big endian support either.

Murali
> 
>>
>> 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