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:

quoted

Hi Niklas

On 12/07/2016 03:20 PM, Niklas Cassel wrote:

quoted

From: Niklas Cassel <redacted>

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 <redacted>
---
 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

quoted

quoted

+        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;