Re: [PATCH V3 2/3] PCI: rcar: Do not abort on too many inbound dma-ranges

From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: marek.vasut@gmail.com
Cc: linux-pci@vger.kernel.org,
	Marek Vasut <marek.vasut+renesas@gmail.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Wolfram Sang <wsa@the-dreams.de>,
	linux-renesas-soc@vger.kernel.org
Subject: Re: [PATCH V3 2/3] PCI: rcar: Do not abort on too many inbound dma-ranges
Date: Wed, 16 Oct 2019 16:00:01 +0100	[thread overview]
Message-ID: <20191016150001.GA7457@e121166-lin.cambridge.arm.com> (raw)
In-Reply-To: <20190809175741.7066-2-marek.vasut@gmail.com>

On Fri, Aug 09, 2019 at 07:57:40PM +0200, marek.vasut@gmail.com wrote:
> From: Marek Vasut <marek.vasut+renesas@gmail.com>
> 
> In case the "dma-ranges" DT property contains either too many ranges
> or the range start address is unaligned in such a way that populating
> the range into the controller requires multiple entries, a situation
> may occur where all ranges cannot be loaded into the controller.
> 
> Currently, the driver refuses to probe in such a situation. Relax this
> behavior, load as many ranges as possible and warn if some ranges do
> not fit anymore.

Patches (1) and (3) are fine but I do not think this one is.

Firmware (DT) should provide dma-ranges according to what HW can handle,
more so given that other subsystems (eg IOMMU) rely on the dma-ranges
value to set-up eg DMA - if there is a mismatch between PCI host inbound
regions and software structures describing DMA'able ranges all bets are
off.

I would not merge this specific patch but let me know what you think.

Thanks,
Lorenzo

> Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
> Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Wolfram Sang <wsa@the-dreams.de>
> Cc: linux-renesas-soc@vger.kernel.org
> To: linux-pci@vger.kernel.org
> ---
> V2: Update on top of 1/3
> V3: No change
> ---
>  drivers/pci/controller/pcie-rcar.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-rcar.c b/drivers/pci/controller/pcie-rcar.c
> index 56a6433eb70b..e2735005ffd3 100644
> --- a/drivers/pci/controller/pcie-rcar.c
> +++ b/drivers/pci/controller/pcie-rcar.c
> @@ -1049,8 +1049,9 @@ static int rcar_pcie_inbound_ranges(struct rcar_pcie *pcie,
>  
>  	while (cpu_addr < cpu_end) {
>  		if (idx >= MAX_NR_INBOUND_MAPS - 1) {
> -			dev_err(pcie->dev, "Failed to map inbound regions!\n");
> -			return -EINVAL;
> +			dev_warn(pcie->dev,
> +				 "Too many inbound regions, not all are mapped.\n");
> +			break;
>  		}
>  		/*
>  		 * Set up 64-bit inbound regions as the range parser doesn't
> -- 
> 2.20.1
> 