linux-kernel - Re: [PATCH v2 2/7] PCI: epf-mhi: Make use of the alignment restriction from EPF core

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Message-ID: <20230826144615.GA8858@thinkpad>
Date:   Sat, 26 Aug 2023 20:16:15 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     lpieralisi@...nel.org, kw@...ux.com, kishon@...nel.org,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 2/7] PCI: epf-mhi: Make use of the alignment
 restriction from EPF core

On Fri, Aug 25, 2023 at 05:50:06PM -0500, Bjorn Helgaas wrote:
> On Mon, Jul 17, 2023 at 12:24:54PM +0530, Manivannan Sadhasivam wrote:
> > Instead of hardcoding the alignment restriction in the EPF_MHI driver, make
> > use of the info available from the EPF core that reflects the alignment
> > restriction of the endpoint controller.
> > 
> > For this purpose, let's introduce the get_align_offset() static function.
> 
> I thought this might be related to the [1/7] patch since they both
> mention an alignment restriction in the EPF core, but [1/7] sets
> pci_epc_features.align and this patch doesn't reference .align, so
> this must be a different alignment restriction?
> 
> I'm sure there's nothing wrong here, and this is already applied, so
> no need to do anything unless .align *should* appear here.
> 

You are absolutely right! The patch was intented to make use of "align" but
"page_size" was used as per old revision. Even though this patch works (because
both "page_size" and "align" were 4K in my setup), it should be fixed.

I will send a fix up patch now. Thanks for spotting.

- Mani

> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  drivers/pci/endpoint/functions/pci-epf-mhi.c | 15 +++++++++++----
> >  1 file changed, 11 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/endpoint/functions/pci-epf-mhi.c b/drivers/pci/endpoint/functions/pci-epf-mhi.c
> > index 9c1f5a154fbd..bb7de6884824 100644
> > --- a/drivers/pci/endpoint/functions/pci-epf-mhi.c
> > +++ b/drivers/pci/endpoint/functions/pci-epf-mhi.c
> > @@ -102,6 +102,11 @@ struct pci_epf_mhi {
> >  	int irq;
> >  };
> >  
> > +static size_t get_align_offset(struct pci_epc *epc, u64 addr)
> > +{
> > +	return addr % epc->mem->window.page_size;
> > +}
> > +
> >  static int __pci_epf_mhi_alloc_map(struct mhi_ep_cntrl *mhi_cntrl, u64 pci_addr,
> >  				 phys_addr_t *paddr, void __iomem **vaddr,
> >  				 size_t offset, size_t size)
> > @@ -134,7 +139,7 @@ static int pci_epf_mhi_alloc_map(struct mhi_ep_cntrl *mhi_cntrl, u64 pci_addr,
> >  {
> >  	struct pci_epf_mhi *epf_mhi = to_epf_mhi(mhi_cntrl);
> >  	struct pci_epc *epc = epf_mhi->epf->epc;
> > -	size_t offset = pci_addr & (epc->mem->window.page_size - 1);
> > +	size_t offset = get_align_offset(epc, pci_addr);
> >  
> >  	return __pci_epf_mhi_alloc_map(mhi_cntrl, pci_addr, paddr, vaddr,
> >  				      offset, size);
> > @@ -161,7 +166,7 @@ static void pci_epf_mhi_unmap_free(struct mhi_ep_cntrl *mhi_cntrl, u64 pci_addr,
> >  	struct pci_epf_mhi *epf_mhi = to_epf_mhi(mhi_cntrl);
> >  	struct pci_epf *epf = epf_mhi->epf;
> >  	struct pci_epc *epc = epf->epc;
> > -	size_t offset = pci_addr & (epc->mem->window.page_size - 1);
> > +	size_t offset = get_align_offset(epc, pci_addr);
> >  
> >  	__pci_epf_mhi_unmap_free(mhi_cntrl, pci_addr, paddr, vaddr, offset,
> >  				 size);
> > @@ -185,7 +190,8 @@ static int pci_epf_mhi_read_from_host(struct mhi_ep_cntrl *mhi_cntrl, u64 from,
> >  				      void *to, size_t size)
> >  {
> >  	struct pci_epf_mhi *epf_mhi = to_epf_mhi(mhi_cntrl);
> > -	size_t offset = from % SZ_4K;
> > +	struct pci_epc *epc = epf_mhi->epf->epc;
> > +	size_t offset = get_align_offset(epc, from);
> >  	void __iomem *tre_buf;
> >  	phys_addr_t tre_phys;
> >  	int ret;
> > @@ -213,7 +219,8 @@ static int pci_epf_mhi_write_to_host(struct mhi_ep_cntrl *mhi_cntrl,
> >  				     void *from, u64 to, size_t size)
> >  {
> >  	struct pci_epf_mhi *epf_mhi = to_epf_mhi(mhi_cntrl);
> > -	size_t offset = to % SZ_4K;
> > +	struct pci_epc *epc = epf_mhi->epf->epc;
> > +	size_t offset = get_align_offset(epc, to);
> >  	void __iomem *tre_buf;
> >  	phys_addr_t tre_phys;
> >  	int ret;
> > -- 
> > 2.25.1
> > 

-- 
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