linux-kernel - Re: [PATCH 1/1] PCI: iproc: Invalidate PAXB address mapping before programming it

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Message-ID: <20191015164303.GC25674@e121166-lin.cambridge.arm.com>
Date:   Tue, 15 Oct 2019 17:43:03 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Abhishek Shah <abhishek.shah@...adcom.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH 1/1] PCI: iproc: Invalidate PAXB address mapping before
 programming it

On Fri, Sep 06, 2019 at 09:28:13AM +0530, Abhishek Shah wrote:
> Invalidate PAXB inbound/outbound address mapping each time before
> programming it. This is helpful for the cases where we need to
> reprogram inbound/outbound address mapping without resetting PAXB.
> kexec kernel is one such example.

This looks like a hack, explain to us please what it actually solves and
why a full reset is not necessary.

> Signed-off-by: Abhishek Shah <abhishek.shah@...adcom.com>
> Reviewed-by: Ray Jui <ray.jui@...adcom.com>
> Reviewed-by: Vikram Mysore Prakash <vikram.prakash@...adcom.com>

Patches are reviewed on public mailing lists, remove tags given
on internal reviews - they are not relevant.

> ---
>  drivers/pci/controller/pcie-iproc.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/pci/controller/pcie-iproc.c b/drivers/pci/controller/pcie-iproc.c
> index e3ca46497470..99a9521ba7ab 100644
> --- a/drivers/pci/controller/pcie-iproc.c
> +++ b/drivers/pci/controller/pcie-iproc.c
> @@ -1245,6 +1245,32 @@ static int iproc_pcie_map_dma_ranges(struct iproc_pcie *pcie)
>  	return ret;
>  }
>  
> +static void iproc_pcie_invalidate_mapping(struct iproc_pcie *pcie)
> +{
> +	struct iproc_pcie_ib *ib = &pcie->ib;
> +	struct iproc_pcie_ob *ob = &pcie->ob;
> +	int idx;
> +
> +	if (pcie->ep_is_internal)

What's this check for and why leaving mappings in place is safe for
this category of IPs ?

> +		return;
> +
> +	if (pcie->need_ob_cfg) {
> +		/* iterate through all OARR mapping regions */
> +		for (idx = ob->nr_windows - 1; idx >= 0; idx--) {
> +			iproc_pcie_write_reg(pcie,
> +					     MAP_REG(IPROC_PCIE_OARR0, idx), 0);
> +		}
> +	}
> +
> +	if (pcie->need_ib_cfg) {
> +		/* iterate through all IARR mapping regions */
> +		for (idx = 0; idx < ib->nr_regions; idx++) {
> +			iproc_pcie_write_reg(pcie,
> +					     MAP_REG(IPROC_PCIE_IARR0, idx), 0);
> +		}
> +	}
> +}
> +
>  static int iproce_pcie_get_msi(struct iproc_pcie *pcie,
>  			       struct device_node *msi_node,
>  			       u64 *msi_addr)
> @@ -1517,6 +1543,8 @@ int iproc_pcie_setup(struct iproc_pcie *pcie, struct list_head *res)
>  	iproc_pcie_perst_ctrl(pcie, true);
>  	iproc_pcie_perst_ctrl(pcie, false);
>  
> +	iproc_pcie_invalidate_mapping(pcie);

It makes more sense to call this in the .shutdown() method if I
understand what it does.

Lorenzo

>  	if (pcie->need_ob_cfg) {
>  		ret = iproc_pcie_map_ranges(pcie, res);
>  		if (ret) {
> -- 
> 2.17.1
>