linux-kernel - Re: [PATCH v3 04/23] dt-bindings: ata: sata: Extend number of SATA ports

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Message-ID: <20220517191539.GA1453482-robh@kernel.org>
Date:   Tue, 17 May 2022 14:15:39 -0500
From:   Rob Herring <robh@...nel.org>
To:     Serge Semin <Sergey.Semin@...kalelectronics.ru>
Cc:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        Rob Herring <robh+dt@...nel.org>,
        Pavel Parkhomenko <Pavel.Parkhomenko@...kalelectronics.ru>,
        linux-ide@...r.kernel.org, Serge Semin <fancer.lancer@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        devicetree@...r.kernel.org,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Hans de Goede <hdegoede@...hat.com>,
        Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
        Alexey Malahov <Alexey.Malahov@...kalelectronics.ru>
Subject: Re: [PATCH v3 04/23] dt-bindings: ata: sata: Extend number of SATA
 ports

On Thu, 12 May 2022 02:17:51 +0300, Serge Semin wrote:
> The denoted in the description upper limit only concerns the Port
> Multipliers, but not the actual SATA ports. It's an external device
> attached to a SATA port in order to access more than one SATA-drive. So
> when it's attached to a SATA port it just extends the port capability
> while the number of actual SATA ports stays the same. For instance on AHCI
> controllers the number of actual ports is determined by the CAP.NP field
> and the PI (Ports Implemented) register. AFAICS in general the maximum
> number of SATA ports depends on the particular controller implementation.
> Generic AHCI controller can't have more than 32 ports (since CAP.NP is of
> 5 bits wide and PI register is 32-bits size), while DWC AHCI SATA
> controller can't be configured with more than 8 ports activated. So let's
> discard the SATA ports reg-property restrictions and just make sure that
> it consists of a single reg-item.
> 
> Signed-off-by: Serge Semin <Sergey.Semin@...kalelectronics.ru>
> 
> ---
> 
> Changelog v2:
> - Add comma and replace "channel" with "SATA port" in the reg property
>   description (@Damien).
> ---
>  Documentation/devicetree/bindings/ata/sata-common.yaml | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 

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