linux-kernel - Re: [Patch v6 1/4] memory: tegra: Add memory controller channels support

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Message-ID: <ba28886f-be5d-9ab2-41d0-942609934263@nvidia.com>
Date:   Mon, 11 Apr 2022 11:35:30 +0530
From:   Ashish Mhetre <amhetre@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, krzysztof.kozlowski@...aro.org,
        thierry.reding@...il.com, jonathanh@...dia.com, robh+dt@...nel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-tegra@...r.kernel.org, krzysztof.kozlowski+dt@...aro.org
Cc:     vdumpa@...dia.com, Snikam@...dia.com
Subject: Re: [Patch v6 1/4] memory: tegra: Add memory controller channels
 support



On 4/10/2022 7:48 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
> 
> 
> 06.04.2022 08:24, Ashish Mhetre пишет:
>> +     num_dt_channels = of_property_count_elems_of_size(pdev->dev.of_node, "reg",
>> +                                                       reg_cells * sizeof(u32));
>> +     /*
>> +      * On tegra186 onwards, memory controller support multiple channels.
>> +      * Apart from regular memory controller channels, there is one broadcast
>> +      * channel and one for stream-id registers.
>> +      */
>> +     if (num_dt_channels < mc->soc->num_channels + 2) {
>> +             dev_warn(&pdev->dev, "MC channels are missing, please update memory controller DT node with MC channels\n");
>> +             return 0;
>> +     }
>> +
>> +     mc->bcast_ch_regs = devm_platform_ioremap_resource_byname(pdev, "mc-broadcast");
>> +     if (IS_ERR(mc->bcast_ch_regs))
>> +             return PTR_ERR(mc->bcast_ch_regs);
> 
> Looks to me that you don't need to use of_property_count_elems_of_size()
> and could only check the "mc-broadcast" presence to decide whether this
> is an older DT.
> 
Now that we are using reg-names in new DT, yes it'd be fine to just
check mc-broadcast to decide it's a new or old DT.

> mc->bcast_ch_regs = devm_platform_ioremap_resource_byname(pdev,
> "broadcast");
> if (IS_ERR(mc->bcast_ch_regs)) {
>          dev_warn(&pdev->dev, "Broadcast channel is missing, please update your
> device-tree\n");
>          return PTR_ERR(mc->bcast_ch_regs);
> }

return 0;

to avoid DT ABI break, right?