linux-kernel - Re: [PATCH 05/12] coresight tmc: Add helpers for accessing 64bit registers

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Date:   Thu, 15 Jun 2017 08:24:14 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Suzuki K Poulose <Suzuki.Poulose@....com>
Cc:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 05/12] coresight tmc: Add helpers for accessing 64bit registers

On 15 June 2017 at 04:13, Suzuki K Poulose <Suzuki.Poulose@....com> wrote:
> On 14/06/17 18:49, Mathieu Poirier wrote:
>>
>> On Mon, Jun 12, 2017 at 03:36:44PM +0100, Suzuki K Poulose wrote:
>>>
>>> Coresight TMC splits 64bit registers into a pair of 32bit registers
>>> (e.g DBA, RRP, RWP). Provide helpers to read/write to these registers.
>>
>>
>> I'm good with this patch but please specify these changes are to support
>> the
>> SoC-600 suite.  That way when we look back at this set in a couple of
>> years we
>> don't loose hair thinking we've been carrying bugs all this time.
>
>
> To be honest, these are not necessarily just for the support of SoC-600.
> It is applies to the current driver with SoC-400, as you could see below,
> where we have always assumed that the RRP/RWP/DBA HI bits are always
> 0. Technically, the TMC supports upto 40bits and hence we have been doing
> it wrong.

I just had another look at the documentation and you are correct -
disregard my comment for this patch.

>
>>> -       read_ptr = readl_relaxed(drvdata->base + TMC_RRP);
>>> -       write_ptr = readl_relaxed(drvdata->base + TMC_RWP);
>>> +       read_ptr = tmc_read_rrp(drvdata);
>>> +       write_ptr = tmc_read_rwp(drvdata);
>
>
>
>
>>> -               writel_relaxed(read_ptr, drvdata->base + TMC_RRP);
>>> +               tmc_write_rrp(drvdata, read_ptr);
>>>                 perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
>
>
>>>         writel_relaxed(axictl, drvdata->base + TMC_AXICTL);
>>> +       tmc_write_dba(drvdata, drvdata->paddr);
>>>
>>> -       writel_relaxed(drvdata->paddr, drvdata->base + TMC_DBALO);
>>> -       writel_relaxed(0x0, drvdata->base + TMC_DBAHI);
>
>
>>>
>>> -       rwp = readl_relaxed(drvdata->base + TMC_RWP);
>>> +       rwp = tmc_read_rwp(drvdata);
>>>         val = readl_relaxed(drvdata->base + TMC_STS);
>>>
>
>
> Suzuki