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

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Message-ID: <20231214104719.GM2938@thinkpad>
Date:   Thu, 14 Dec 2023 16:17:19 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
Cc:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        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 Thu, Dec 14, 2023 at 03:44:21PM +0530, Krishna Chaitanya Chundru wrote:
> 
> 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;
> 	}

Are you reading the patch correctly? Please take a look at this commit:
https://git.kernel.org/pub/scm/linux/kernel/git/mani/mhi.git/tree/drivers/pci/endpoint/functions/pci-epf-mhi.c?h=mhi-next&id=d1c6f4ba4746ed41fde8269cb5fea88bddb60504#n771

- Mani

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

-- 
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