netdev - Re: [PATCH v3 3/6] net: stmmac: stmmac_platform: fix parsing of DT binding

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Message-ID: <90ea49d4-91de-0a5b-d379-11c60b6ccb73@st.com>
Date:   Thu, 8 Dec 2016 10:54:20 +0100
From:   Alexandre Torgue <alexandre.torgue@...com>
To:     Niklas Cassel <niklas.cassel@...s.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 3/6] net: stmmac: stmmac_platform: fix parsing of DT
 binding

Hi

On 12/08/2016 10:46 AM, Niklas Cassel wrote:
> On 12/08/2016 10:02 AM, Alexandre Torgue wrote:
>> Hi Niklas
>>
>> On 12/07/2016 03:20 PM, Niklas Cassel wrote:
>>> From: Niklas Cassel <niklas.cassel@...s.com>
>>>
>>> commit 64c3b252e9fc ("net: stmmac: fixed the pbl setting with DT")
>>> changed the parsing of the DT binding.
>>>
>>> Before 64c3b252e9fc, snps,fixed-burst and snps,mixed-burst were parsed
>>> regardless if the property snps,pbl existed or not.
>>> After the commit, fixed burst and mixed burst are only parsed if
>>> snps,pbl exists. Now when snps,aal has been added, it too is only
>>> parsed if snps,pbl exists.
>>>
>>> Since the DT binding does not specify that fixed burst, mixed burst
>>> or aal depend on snps,pbl being specified, undo changes introduced
>>> by 64c3b252e9fc.
>>>
>>> The issue commit 64c3b252e9fc ("net: stmmac: fixed the pbl setting with
>>> DT") tries to address is solved in another way:
>>> The databook specifies that all values other than
>>> 1, 2, 4, 8, 16, or 32 results in undefined behavior,
>>> so snps,pbl = <0> is invalid.
>>>
>>> If pbl is 0 after parsing, set pbl to DEFAULT_DMA_PBL.
>>> This handles the case where the property is omitted, and also handles
>>> the case where the property is specified without any data.
>>>
>>> Signed-off-by: Niklas Cassel <niklas.cassel@...s.com>
>>> ---
>>>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c  |  4 +--
>>>  .../net/ethernet/stmicro/stmmac/stmmac_platform.c  | 29 +++++++++++-----------
>>>  2 files changed, 17 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>> index b1e42ddf0370..b5188122bc15 100644
>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
>>> @@ -1581,8 +1581,8 @@ static int stmmac_init_dma_engine(struct stmmac_priv *priv)
>>>      int atds = 0;
>>>      int ret = 0;
>>>
>>> -    if (!priv->plat->dma_cfg) {
>>> -        dev_err(priv->device, "DMA configuration not found\n");
>>> +    if (!priv->plat->dma_cfg || !priv->plat->dma_cfg->pbl) {
>>
>> How "priv->plat->dma_cfg->pbl" could be equal to 0 if you force it to DEFAULT_DMA_PBL in "stmmac_probe_config_dt" in case of DT doesn't set pbl value?
>
> The PCI glue code does not call stmmac_probe_config_dt.
>
> Also any glue driver could override the value set by stmmac_probe_config_dt
> before calling stmmac_dvr_probe. So I guess if we want any trustworthy
> sanity-checking, it actually has to be done in stmmac_main.c.

Ok I see, it is more safe. You can add my Acked-by.

Thanks
Alex

>
>
>>
>>
>>> +        dev_err(priv->device, "Invalid DMA configuration\n");
>>>          return -EINVAL;
>>>      }
>>>
>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>>> index d3b6f92f350a..81800f23a9c4 100644
>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>>> @@ -304,21 +304,22 @@ stmmac_probe_config_dt(struct platform_device *pdev, const char **mac)
>>>          plat->force_sf_dma_mode = 1;
>>>      }
>>>
>>> -    if (of_find_property(np, "snps,pbl", NULL)) {
>>> -        dma_cfg = devm_kzalloc(&pdev->dev, sizeof(*dma_cfg),
>>> -                       GFP_KERNEL);
>>> -        if (!dma_cfg) {
>>> -            stmmac_remove_config_dt(pdev, plat);
>>> -            return ERR_PTR(-ENOMEM);
>>> -        }
>>> -        plat->dma_cfg = dma_cfg;
>>> -        of_property_read_u32(np, "snps,pbl", &dma_cfg->pbl);
>>> -        dma_cfg->aal = of_property_read_bool(np, "snps,aal");
>>> -        dma_cfg->fixed_burst =
>>> -            of_property_read_bool(np, "snps,fixed-burst");
>>> -        dma_cfg->mixed_burst =
>>> -            of_property_read_bool(np, "snps,mixed-burst");
>>> +    dma_cfg = devm_kzalloc(&pdev->dev, sizeof(*dma_cfg),
>>> +                   GFP_KERNEL);
>>> +    if (!dma_cfg) {
>>> +        stmmac_remove_config_dt(pdev, plat);
>>> +        return ERR_PTR(-ENOMEM);
>>>      }
>>> +    plat->dma_cfg = dma_cfg;
>>> +
>>> +    of_property_read_u32(np, "snps,pbl", &dma_cfg->pbl);
>>> +    if (!dma_cfg->pbl)
>>> +        dma_cfg->pbl = DEFAULT_DMA_PBL;
>>> +
>>> +    dma_cfg->aal = of_property_read_bool(np, "snps,aal");
>>> +    dma_cfg->fixed_burst = of_property_read_bool(np, "snps,fixed-burst");
>>> +    dma_cfg->mixed_burst = of_property_read_bool(np, "snps,mixed-burst");
>>> +
>>>      plat->force_thresh_dma_mode = of_property_read_bool(np, "snps,force_thresh_dma_mode");
>>>      if (plat->force_thresh_dma_mode) {
>>>          plat->force_sf_dma_mode = 0;
>>>
>