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

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Message-ID: <37548a54-c54b-3194-691a-22fa8118ed3d@ti.com>
Date:   Thu, 10 Nov 2016 10:37:29 -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 11/09/2016 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.

> 
>>
>>> 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 :(

-- 
regards,
-grygorii