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

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Date:   Mon, 16 May 2022 16:01:54 -0500
From:   Rob Herring <robh@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        Frank Li <Frank.Li@....com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 12/17] PCI: dwc: Add iATU regions size detection
 procedure

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@...kalelectronics.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@...nel.org>