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

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Message-ID: <20190906083816.GD9720@e119886-lin.cambridge.arm.com>
Date:   Fri, 6 Sep 2019 09:38:17 +0100
From:   Andrew Murray <andrew.murray@....com>
To:     Abhishek Shah <abhishek.shah@...adcom.com>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        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.

Why is this approach better than resetting the PAXB (I assume that's
the PCI controller IP)? Wouldn't resetting the PAXB address this issue,
and ensure that no other configuration is left behind?

Or is this related to earlier boot stages loading firmware for the emulated
downstream endpoints (ep_is_internal)?

Finally, in the case where ep_is_internal do you need to disable anything
prior to invalidating the mappings?

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

The code changes look good to me.

Thanks,

Andrew Murray

> -- 
> 2.17.1
>