Re: [PATCH v2 12/17] PCI: dwc: Add iATU regions size detection procedure

From: Rob Herring <robh@kernel.org>
To: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: "Jingoo Han" <jingoohan1@gmail.com>,
	"Gustavo Pimentel" <gustavo.pimentel@synopsys.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Serge Semin" <fancer.lancer@gmail.com>,
	"Alexey Malahov" <Alexey.Malahov@baikalelectronics.ru>,
	"Pavel Parkhomenko" <Pavel.Parkhomenko@baikalelectronics.ru>,
	"Frank Li" <Frank.Li@nxp.com>,
	"Manivannan Sadhasivam" <manivannan.sadhasivam@linaro.org>,
	linux-pci@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 12/17] PCI: dwc: Add iATU regions size detection procedure
Date: Mon, 16 May 2022 16:01:54 -0500	[thread overview]
Message-ID: <20220516210154.GH3209795-robh@kernel.org> (raw)
In-Reply-To: <20220503214638.1895-13-Sergey.Semin@baikalelectronics.ru>

On Wed, May 04, 2022 at 12:46:33AM +0300, Serge Semin wrote:
> Depending on the DWC PCIe RC/EP/DM IP-core configuration parameters the
> controllers can be equipped not only with various number of inbound and
> outbound iATU windows, but with varied regions settings like alignment
> (which is also the minimum window size), minimum and maximum sizes. So to
> speak if internal ATU is enabled for the denoted IP-cores then the former
> settings will be defined by the CX_ATU_MIN_REGION_SIZE parameter while the
> later one will be determined by the CX_ATU_MAX_REGION_SIZE configuration
> parameter. Anyway having these parameters used in the driver will help to
> verify whether the requested inbound or outbound memory mappings can be
> fully created. Currently the driver doesn't perform any corresponding
> checking.
> 
> Note 1. The extended iATU regions have been supported since DWC PCIe
> v4.60a. There is no need in testing the upper limit register availability
> for the older cores.
> 
> Note 2. The regions alignment is determined with using the fls() method
> since the lower four bits of the ATU Limit register can be occupied with
> the Circular Buffer Increment setting, which can be initialized with
> zeros.
> 
> The (dma-)ranges verification will be added a bit later in one of the next
> commits.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 33 +++++++++++++++++---
>  drivers/pci/controller/dwc/pcie-designware.h |  2 ++
>  2 files changed, 31 insertions(+), 4 deletions(-)

Reviewed-by: Rob Herring <robh@kernel.org>