netdev - Re: [PATCH] net: ethernet: ti: davinci_cpdma: fix fixed prio cpdma ctlr configuration

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Date:   Thu, 10 Nov 2016 16:58:41 -0600
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     "ivan.khoronzhuk" <ivan.khoronzhuk@...aro.org>,
        <mugunthanvnm@...com>, <netdev@...r.kernel.org>
CC:     <linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: ethernet: ti: davinci_cpdma: fix fixed prio cpdma
 ctlr configuration



On 11/10/2016 01:52 PM, ivan.khoronzhuk wrote:
>
>
> On 10.11.16 18:37, Grygorii Strashko wrote:
>>
>>
>> On 11/09/2016 05:56 PM, Ivan Khoronzhuk wrote:
>>>
>>>
>>> On 09.11.16 23:09, Grygorii Strashko wrote:
>>>>
>>>>
>>>> On 11/08/2016 07:10 AM, Ivan Khoronzhuk wrote:
>>>>> The dma ctlr is reseted to 0 while cpdma start, thus cpdma ctlr
>>>>
>>>> I assume this is because cpdma_ctlr_start() does soft reset. Is it
>>>> correct?
>>> Probably not. I've seen this register doesn't hold any previous settings
>>> (just trash)
>>
>> What register CPDMA_DMACONTROL or CPSW_DMACTRL?
>>
>>> after cpdma_ctlr_stop(), actually after last channel is stopped (inside
>>> of cpdma_ctlr_stop()).
>>
>> So, You are stating that Registers context is changed after stop?
>>
>>> Then cpdma_ctlr_start() just reset it to 0.
>>
>> "just trash" or "0".
>>
>> Sry, I do not see how cpdma_ctlr_stop() can affect on registers state :(
>> and I'd very appreciated if can provide more detailed information.
>>
> I've checked again, it was my mistake. It simply reset to 0 while soft
> reset.
>
>>>
>>>>
>>>>> cannot be configured after cpdma is stopped. So, restore content
>>>>> of cpdma ctlr while off/on procedure.
>>>>>
>>>>> Based on net-next/master
>>>>
>>>> ^ remove it
>>> sure
>>>
>>>>
>>>>>
>>>>> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
>>>>> ---
>>>>>  drivers/net/ethernet/ti/cpsw.c          |   6 +-
>>>>>  drivers/net/ethernet/ti/davinci_cpdma.c | 103
>>>>> +++++++++++++++++---------------
>>>>>  drivers/net/ethernet/ti/davinci_cpdma.h |   2 +
>>>>>  3 files changed, 58 insertions(+), 53 deletions(-)
>>>>>
>>>>> diff --git a/drivers/net/ethernet/ti/cpsw.c
>>>>> b/drivers/net/ethernet/ti/cpsw.c
>>>>> index b1ddf89..4d04b8e 100644
>>>>> --- a/drivers/net/ethernet/ti/cpsw.c
>>>>> +++ b/drivers/net/ethernet/ti/cpsw.c
>>>>> @@ -1376,10 +1376,6 @@ static int cpsw_ndo_open(struct net_device
>>>>> *ndev)
>>>>>                    ALE_ALL_PORTS, ALE_ALL_PORTS, 0, 0);
>>>>>
>>>>>      if (!cpsw_common_res_usage_state(cpsw)) {
>>>>> -        /* setup tx dma to fixed prio and zero offset */
>>>>> -        cpdma_control_set(cpsw->dma, CPDMA_TX_PRIO_FIXED, 1);
>>>>> -        cpdma_control_set(cpsw->dma, CPDMA_RX_BUFFER_OFFSET, 0);
>>>>> -
>>>>>          /* disable priority elevation */
>>>>>          __raw_writel(0, &cpsw->regs->ptype);
>>>>>
>>>>> @@ -2710,6 +2706,8 @@ static int cpsw_probe(struct platform_device
>>>>> *pdev)
>>>>>      dma_params.desc_align        = 16;
>>>>>      dma_params.has_ext_regs        = true;
>>>>>      dma_params.desc_hw_addr         = dma_params.desc_mem_phys;
>>>>> +    dma_params.rxbuf_offset        = 0;
>>>>> +    dma_params.fixed_prio        = 1;
>>>>
>>>> Do we really need this new parameters? Do you have plans to use other
>>>> values?
>>> I'm ok if this is static (equally as a bunch of rest in dma_params), no
>>> see reason to use other values,
>>
>> That's what i wanted to know :) - go static, pls.
>>
>>> it at least now. But the issue is not only in these two parameters and
>>> not only in cpsw_ndo_open().
>>> It touches cpsw_set_channels() also, where ctlr stop/start is present.
>>> In order to not copy cpdma_control_set(cpsw->dma, CPDMA_TX_PRIO_FIXED,
>>> 1)...
>>> in all such kind places in eth drivers, better to allow the cpdma to
>>> control it's parameters...
>>>
>>> The cpdma ctlr register holds a little more parameters (but only two of
>>> them are set in cpsw)
>>> Maybe there is reason to save them also. Actually I'd seen this problem
>>> when playing with
>>> on/off channel shapers, unfortunately the cpdma ctlr holds this info
>>> also, and it was lost
>>> while on/off (but I'm going to restore it in chan_start()).
>>>
>>
>> I understand you change, but I'm note sure about real root cause :(
> so, are you Ok with current version?

No. pls, use constant values and do not introduce additional parameters.
Also, pls update commit message with new information.

-- 
regards,
-grygorii