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

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Date:   Thu, 10 Nov 2016 01:56:44 +0200
From:   Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:     Grygorii Strashko <grygorii.strashko@...com>, 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 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)
after cpdma_ctlr_stop(), actually after last channel is stopped (inside of cpdma_ctlr_stop()).
Then cpdma_ctlr_start() just reset it to 0.

>
>> 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,
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()).


>

-- 
Regards,
Ivan Khoronzhuk