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Subject: Re: [PATCH 1/4] dmaengine: qcom: bam_dma: make bam clk optional
To:     Vinod Koul <vinod.koul@intel.com>
Cc:     Andy Gross <andy.gross@linaro.org>, dmaengine@vger.kernel.org,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        David Brown <david.brown@linaro.org>,
        Dan Williams <dan.j.williams@intel.com>,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org,
        yanhe@quicinc.com, ramkri@qti.qualcomm.com, sdharia@quicinc.com
References: <20180116190236.14558-1-srinivas.kandagatla@linaro.org>
 <20180116190236.14558-2-srinivas.kandagatla@linaro.org>
 <20180119055221.GV18649@localhost>
 <8dfa8ba1-6e98-a8e4-614c-592861cef571@linaro.org>
 <20180123091905.GY18649@localhost>
From:   Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Message-ID: <86774341-19e6-5653-49ae-cb7614490d1b@linaro.org>
Date:   Tue, 23 Jan 2018 09:20:30 +0000
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On 23/01/18 09:19, Vinod Koul wrote:
> On Mon, Jan 22, 2018 at 09:55:01AM +0000, Srinivas Kandagatla wrote:
> 
>>>> @@ -1180,13 +1180,14 @@ static int bam_dma_probe(struct platform_device *pdev)
>>>>   						"qcom,controlled-remotely");
>>>>   	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
>>>
>>> but you still do clk_get unconditionally?
>>
>> Only reason to do this way is to not break existing users in the mainline.
>>
>> remotely controlled BAM is already supported in upstream driver, there are
>> users of this who pass clk from device tree, If I make this conditional then
>> subsequent reads to the BAM registers for those instances might crash the
>> system.
> 
> But these instances are remote controlled, so if we stop representing them
> in Linux, why would we read them?

Plan is that we would transition those users once we get these 
bindings/changes in. Currently I don't have access to any of those 
devices so I made the changes safe, such that it does not break devices 
on mainline.

--srini

>