Re: Question about EMMC CMDQ HOST CONTROLLER INTERFACE (CQHCI) DRIVER

[Adrian Hunter <adrian.hunter@intel.com>]

On 10/11/22 04:11, Jyan Chou [周芷安] wrote:
>> CQHCI has its own DMA descriptors, so maybe a similar change is needed for CQHCI?
>> So you do need a similar change for CQHCI
> 
>>> According to these comments, it is acceptable for us to update a patch to solve the limitation of 128MB boundary ?
> 	We have a patch and it works well on cmdq case.
> 	Thanks. 

If you have a patch, you can of course submit it.

> 
> -----Original Message-----
> From: Shawn Lin <shawn.lin@rock-chips.com> 
> Sent: Wednesday, November 9, 2022 11:46 AM
> To: Jyan Chou [周芷安] <jyanchou@realtek.com>
> Cc: shawn.lin@rock-chips.com; linux-mmc <linux-mmc@vger.kernel.org>; Jisheng.Zhang@synaptics.com; Adrian Hunter <adrian.hunter@intel.com>
> Subject: Re: Question about EMMC CMDQ HOST CONTROLLER INTERFACE (CQHCI) DRIVER
> 
> 
> On 2022/11/8 17:19, Jyan Chou [周芷安] wrote:
>>> CQHCI has its own DMA descriptors, so maybe a similar change is needed for CQHCI?
>>
>> I didn't find this limitation in synopsys DW IP databook.
>>>> I found it on page 84
> 
> I see, but it wasn't clear to me if this description on P84 is for CQ engine part as well.  But seems yes after checking with the IP vendor.
> So you do need a similar change for CQHCI in cqhci_host_alloc_tdl.
> 
>>
>> -----Original Message-----
>> From: Shawn Lin <shawn.lin@rock-chips.com>
>> Sent: Tuesday, November 8, 2022 5:15 PM
>> To: Adrian Hunter <adrian.hunter@intel.com>
>> Cc: shawn.lin@rock-chips.com; linux-mmc <linux-mmc@vger.kernel.org>; 
>> Jyan Chou [周芷安] <jyanchou@realtek.com>; Jisheng.Zhang@synaptics.com
>> Subject: Re: Question about EMMC CMDQ HOST CONTROLLER INTERFACE 
>> (CQHCI) DRIVER
>>
>> + Jisheng Zhang
>>
>> On 2022/11/8 16:34, Adrian Hunter wrote:
>>> On 8/11/22 10:28, Shawn Lin wrote:
>>>> On 2022/11/8 16:20, Adrian Hunter wrote:
>>>>> On 8/11/22 09:25, Jyan Chou [周芷安] wrote:
>>>>>> Hello Adrian Hunter,
>>>>>>
>>>>>> We are now using the upstream code of EMMC CMDQ HOST CONTROLLER INTERFACE (CQHCI) DRIVER, but we found that the existing driver cannot support the limitation of Synopsys IP.
>>>>>>
>>>>>> Synopsys IP has a description on their data book " While using DMA, the host memory data buffer size and start address must not exceed 128 MB".
>>>>
>>>> Synopsys-based SDHCI IP does have a limitation of 128MB boundary. 
>>>> But it has already been solved by upstream driver.
>>>>
>>>> FYI:
>>>>
>>>> commit b85c997d2cfefe7d1f706b85ae46e35a50e3131c ("mmc:
>>>> sdhci-of-dwcmshc: solve 128MB DMA boundary limitation")
>>>
>>> CQHCI has its own DMA descriptors, so maybe a similar change is needed for CQHCI?
>>
>> I didn't find this limitation in synopsys DW IP databook.
>>
>>>
>>>>
>>>>>>
>>>>>> I am wondering whether there is a method or patch that can fix this boundary limitation.
>>>>>> Thanks.
>>>>>> Best Regards,
>>>>>> Jyan Chou
>>>>>
>>>>> Hello Jyan Chou
>>>>>
>>>>> I am not clear on what the exact limitation is.  The driver never uses buffers as big as 128 MB.
>>>>> To restrict DMA to low memory addresses a DMA mask can be used.
>>>>>
>>>>> But perhaps you mean not to cross a 128 MB boundary?
>>>>>
>>>>> Please cc your questions to the linux kernel mmc mailing list:
>>>>> linux-mmc@vger.kernel.org because others can answer too.
>>>>>
>>>>> Regards
>>>>> Adrian
>>>
>>
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