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From:   Doug Anderson <dianders@chromium.org>
Date:   Wed, 11 Jul 2018 11:37:07 -0700
Message-ID: <CAD=FV=UGjf+qSfzYbQ1OEydEWJH2e8vhNiOPAytPH_rnkabq3Q@mail.gmail.com>
Subject: Re: [PATCH v6 2/7] thermal: tsens: Add support to split up register
 address space into two
To:     Amit Kucheria <amit.kucheria@linaro.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Rajendra Nayak <rnayak@codeaurora.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Eduardo Valentin <edubezval@gmail.com>,
        smohanad@codeaurora.org,
        Vivek Gautam <vivek.gautam@codeaurora.org>,
        Andy Gross <andy.gross@linaro.org>,
        Zhang Rui <rui.zhang@intel.com>, linux-pm@vger.kernel.org
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Sender: linux-kernel-owner@vger.kernel.org
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Hi,

On Mon, Jul 9, 2018 at 4:43 AM, Amit Kucheria <amit.kucheria@linaro.org> wrote:
> There are two banks of registers for v2 TSENS IPs: SROT and TM. On older
> SoCs these were contiguous, leading to DTs mapping them as one register
> address space of size 0x2000. In newer SoCs, these two banks are not
> contiguous anymore.
>
> Fixing old DTs to split the address space into allows us to have cleaner
> common code e.g. get_temp() that is shared across new and old platforms.

This makes it sound like old DTs won't be supported anymore.  ...but
the code says otherwise.  I'd just remove the above paragraph.


> @@ -126,11 +127,21 @@ static const struct regmap_config tsens_config = {
>  int __init init_common(struct tsens_device *tmdev)
>  {
>         void __iomem *base;
> +       struct platform_device *op = of_find_device_by_node(tmdev->dev->of_node);
>
> +       if (!op)
> +               return -EINVAL;
>         base = of_iomap(tmdev->dev->of_node, 0);
>         if (!base)
>                 return -EINVAL;
>
> +       if (op->num_resources > 1) {

Maybe add a comment here that says that we don't actually map the SROT
yet because you don't read anything from there?  I kept getting
confused about how this patch could possibly work with no code to map
SROT...

> +               tmdev->tm_offset = 0;
> +       } else {
> +               /* old DTs where SROT and TM were in a contiguous 2K block */
> +               tmdev->tm_offset = 0x1000;

This patch without patch #4 will break compatibility.  You should
squash part of patch #4 into this one, specifically:

-#define STATUS_OFFSET 0x10a0
-#define LAST_TEMP_MASK 0xfff
+#define STATUS_OFFSET 0xa0
+#define LAST_TEMP_MASK 0xfff

Without that you break bisect-ability and also confuse anyone trying
to look at this patch.

-Doug