linux-kernel - Re: [PATCH 2/4] clk: tegra: check BPMP response return code

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Date:   Mon, 2 Oct 2017 21:23:35 +0100
From:   Jon Hunter <jonathanh@...dia.com>
To:     Timo Alho <talho@...dia.com>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>
CC:     "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] clk: tegra: check BPMP response return code


On 02/10/17 09:43, Timo Alho wrote:
> 
> 
> On 29.09.2017 17:53, Jonathan Hunter wrote:
>>
>> On 29/09/17 14:46, Timo Alho wrote:
>>> Hi Jon,
>>>
>>> On 21.09.2017 14:21, Jonathan Hunter wrote:
>>>>
>>>>
>>>> On 07/09/17 10:31, Timo Alho wrote:
>>>>> Check return code in BPMP response message(s). The typical error case
>>>>> is when clock operation is attempted with invalid clock identifier.
>>>>>
>>>>> Also remove error print from call to clk_get_info() as the
>>>>> implementation loops through range of all possible identifier, but the
>>>>> operation is expected error out when the clock id is unused.
>>>>>
>>>>> Signed-off-by: Timo Alho <talho@...dia.com>
>>>>> ---
>>>>>    drivers/clk/tegra/clk-bpmp.c | 15 ++++++++++-----
>>>>>    1 file changed, 10 insertions(+), 5 deletions(-)
>>>>>
>>>>> diff --git a/drivers/clk/tegra/clk-bpmp.c
>>>>> b/drivers/clk/tegra/clk-bpmp.c
>>>>> index 638ace6..a896692 100644
>>>>> --- a/drivers/clk/tegra/clk-bpmp.c
>>>>> +++ b/drivers/clk/tegra/clk-bpmp.c
>>>>> @@ -55,6 +55,7 @@ struct tegra_bpmp_clk_message {
>>>>>        struct {
>>>>>            void *data;
>>>>>            size_t size;
>>>>> +        int ret;
>>>>>        } rx;
>>>>>    };
>>>>>    @@ -64,6 +65,7 @@ static int tegra_bpmp_clk_transfer(struct
>>>>> tegra_bpmp *bpmp,
>>>>>        struct mrq_clk_request request;
>>>>>        struct tegra_bpmp_message msg;
>>>>>        void *req = &request;
>>>>> +    int err;
>>>>>          memset(&request, 0, sizeof(request));
>>>>>        request.cmd_and_id = (clk->cmd << 24) | clk->id;
>>>>> @@ -84,7 +86,13 @@ static int tegra_bpmp_clk_transfer(struct
>>>>> tegra_bpmp *bpmp,
>>>>>        msg.rx.data = clk->rx.data;
>>>>>        msg.rx.size = clk->rx.size;
>>>>>    -    return tegra_bpmp_transfer(bpmp, &msg);
>>>>> +    err = tegra_bpmp_transfer(bpmp, &msg);
>>>>> +    if (err < 0)
>>>>> +        return err;
>>>>> +    else if (msg.rx.ret < 0)
>>>>> +        return -EINVAL;
>>>>
>>>> I assume that the error codes returned do not correlated to the Linux
>>>> error codes here. Is that correct? If not we could just return the
>>>> actual error code. Otherwise would it be useful to print a message with
>>>> the bpmp error code for debug?
>>>
>>> The error codes are not 1:1 match with Linux. Unfortunately, printing
>>> message for debug is not either viable as during clock probing we are
>>> expecting many of the calls to return -BPMP_EINVAL to indicate that
>>> particular clock ID is unused.
>>
>> OK. Could it return other errors other than BPMP_EINVAL? I am just
>> wondering if we need to differentiate between unused and an actual
>> error? Maybe that is not possible here?
> 
> Other error codes are possible (though they are not explicitly
> documented in abi header). It's not easy to differentiate the error code
> at this level: -BPMP_EINVAL is "expected" condition with
> CMD_CLK_GET_ALL_INFO, whereas -BPMP_EINVAL is true error on other commands.

OK, thanks for clarifying.

Acked-by: Jon Hunter <jonathanh@...dia.com>

Cheers
Jon

-- 
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