linux-kernel - Re: [PATCH 6/9] PCI: epf-mhi: Enable MHI async read/write support

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Date:   Thu, 14 Dec 2023 15:44:21 +0530
From:   Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
CC:     <lpieralisi@...nel.org>, <kw@...ux.com>, <kishon@...nel.org>,
        <bhelgaas@...gle.com>, <mhi@...ts.linux.dev>,
        <linux-arm-msm@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 6/9] PCI: epf-mhi: Enable MHI async read/write support


On 12/14/2023 3:39 PM, Manivannan Sadhasivam wrote:
> On Thu, Dec 14, 2023 at 03:10:01PM +0530, Krishna Chaitanya Chundru wrote:
>> On 11/27/2023 6:15 PM, Manivannan Sadhasivam wrote:
>>> Now that both eDMA and iATU are prepared to support async transfer, let's
>>> enable MHI async read/write by supplying the relevant callbacks.
>>>
>>> In the absence of eDMA, iATU will be used for both sync and async
>>> operations.
>>>
>>> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>>> ---
>>>    drivers/pci/endpoint/functions/pci-epf-mhi.c | 7 ++++---
>>>    1 file changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/pci/endpoint/functions/pci-epf-mhi.c b/drivers/pci/endpoint/functions/pci-epf-mhi.c
>>> index 3d09a37e5f7c..d3d6a1054036 100644
>>> --- a/drivers/pci/endpoint/functions/pci-epf-mhi.c
>>> +++ b/drivers/pci/endpoint/functions/pci-epf-mhi.c
>>> @@ -766,12 +766,13 @@ static int pci_epf_mhi_link_up(struct pci_epf *epf)
>>>    	mhi_cntrl->raise_irq = pci_epf_mhi_raise_irq;
>>>    	mhi_cntrl->alloc_map = pci_epf_mhi_alloc_map;
>>>    	mhi_cntrl->unmap_free = pci_epf_mhi_unmap_free;
>>> +	mhi_cntrl->read_sync = mhi_cntrl->read_async = pci_epf_mhi_iatu_read;
>>> +	mhi_cntrl->write_sync = mhi_cntrl->write_async = pci_epf_mhi_iatu_write;
>>>    	if (info->flags & MHI_EPF_USE_DMA) {
>>>    		mhi_cntrl->read_sync = pci_epf_mhi_edma_read;
>>>    		mhi_cntrl->write_sync = pci_epf_mhi_edma_write;
>>> -	} else {
>>> -		mhi_cntrl->read_sync = pci_epf_mhi_iatu_read;
>>> -		mhi_cntrl->write_sync = pci_epf_mhi_iatu_write;
>>> +		mhi_cntrl->read_async = pci_epf_mhi_edma_read_async;
>>> +		mhi_cntrl->write_async = pci_epf_mhi_edma_write_async;
>> I think the read_async & write async should be updated inside the if
>> condition where MHI_EPF_USE_DMA flag is set.
>>
> That's what being done here. Am I missing anything?
>
> - Mani

It should be like this as edma sync & aysnc read write should be update 
only if DMA is supported, in the patch I see async function pointers are 
being updated with the edma function pointers for IATU operations.

                 if (info->flags & MHI_EPF_USE_DMA) {

   		mhi_cntrl->read_sync = pci_epf_mhi_edma_read;
   		mhi_cntrl->write_sync = pci_epf_mhi_edma_write;
		mhi_cntrl->read_async = pci_epf_mhi_edma_read_async;
		mhi_cntrl->write_async = pci_epf_mhi_edma_write_async;
	}
- Krishna Chaitanya.

>> - Krishna Chaitanya.
>>
>>>    	}
>>>    	/* Register the MHI EP controller */