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

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Date:   Mon, 11 Apr 2022 09:33:46 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Ashish Mhetre <amhetre@...dia.com>,
        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 4/11/22 09:05, Ashish Mhetre wrote:
> 
> 
> 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?

Yes, it should be "return 0".