linux-kernel - Re: [PATCH v5 8/8] PCI: dwc: Do not write to MSI control registers if the platform doesn't use it

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Date:   Wed, 3 Apr 2019 18:19:03 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Murali Karicheri <m-karicheri2@...com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Jingoo Han <jingoohan1@...il.com>, linux-pci@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 8/8] PCI: dwc: Do not write to MSI control registers
 if the platform doesn't use it

On Thu, Mar 21, 2019 at 03:29:27PM +0530, Kishon Vijay Abraham I wrote:
> Platforms which populate msi_host_init, has it's own MSI controller
> logic. Writing to MSI control registers on platforms which doesn't use
> Designware's MSI controller logic might have side effects. To
> be safe, do not write to MSI control registers if the platform uses
> it's own MSI controller logic instead of Designware's MSI controller
> logic.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> ---
>  .../pci/controller/dwc/pcie-designware-host.c | 24 ++++++++++---------
>  1 file changed, 13 insertions(+), 11 deletions(-)

This patch is needed regardless of the rest of the series, correct ?
A.k.a. it is fixing an issue already in the mainline.

Just to make sure we are not _introducing_ a bisection issue with this
series up to this patch, in which case I will squash this patch into one
of the previous ones, please let me know.

Thanks,
Lorenzo

> diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c b/drivers/pci/controller/dwc/pcie-designware-host.c
> index 498422397609..7e0ff7d428a9 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> @@ -626,17 +626,19 @@ void dw_pcie_setup_rc(struct pcie_port *pp)
>  
>  	dw_pcie_setup(pci);
>  
> -	num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
> -
> -	/* Initialize IRQ Status array */
> -	for (ctrl = 0; ctrl < num_ctrls; ctrl++) {
> -		pp->irq_mask[ctrl] = ~0;
> -		dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_MASK +
> -					(ctrl * MSI_REG_CTRL_BLOCK_SIZE),
> -				    4, pp->irq_mask[ctrl]);
> -		dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_ENABLE +
> -					(ctrl * MSI_REG_CTRL_BLOCK_SIZE),
> -				    4, ~0);
> +	if (!pp->ops->msi_host_init) {
> +		num_ctrls = pp->num_vectors / MAX_MSI_IRQS_PER_CTRL;
> +
> +		/* Initialize IRQ Status array */
> +		for (ctrl = 0; ctrl < num_ctrls; ctrl++) {
> +			pp->irq_mask[ctrl] = ~0;
> +			dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_MASK +
> +					    (ctrl * MSI_REG_CTRL_BLOCK_SIZE),
> +					    4, pp->irq_mask[ctrl]);
> +			dw_pcie_wr_own_conf(pp, PCIE_MSI_INTR0_ENABLE +
> +					    (ctrl * MSI_REG_CTRL_BLOCK_SIZE),
> +					    4, ~0);
> +		}
>  	}
>  
>  	/* Setup RC BARs */
> -- 
> 2.17.1
>