Re: [PATCH 2/6] net: stmmac: fix csr_clk can't be zero issue

From: Alexandre Torgue
Date: Mon Apr 29 2019 - 04:27:18 EST




On 4/29/19 10:09 AM, biao huang wrote:
Hi,

On Mon, 2019-04-29 at 09:18 +0200, Alexandre Torgue wrote:
Hi

On 4/28/19 8:30 AM, Biao Huang wrote:
The specific clk_csr value can be zero, and
stmmac_clk is necessary for MDC clock which can be set dynamically.
So, change the condition from plat->clk_csr to plat->stmmac_clk to
fix clk_csr can't be zero issue.

Signed-off-by: Biao Huang <biao.huang@xxxxxxxxxxxx>
---
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 818ad88..9e89b94 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4376,7 +4376,7 @@ int stmmac_dvr_probe(struct device *device,
* set the MDC clock dynamically according to the csr actual
* clock input.
*/
- if (!priv->plat->clk_csr)
+ if (priv->plat->stmmac_clk)
stmmac_clk_csr_set(priv);
else
priv->clk_csr = priv->plat->clk_csr;


So, as soon as stmmac_clk will be declared, it is no longer possible to
fix a CSR through the device tree ?

let's focus on the condition:
1. clk_csr may be zero, it should not be the condition. or the clk_csr =
0 will jump to the wrong block.
2. Since stmmac_clk_csr_set will get_clk_rate from stmmac_clk,
the plat->stmmac_clk is a more proper condition.


Ok, but here you remove one possibility: stmmac_clk and clk_csr defined. no ?

Other way could be the following code + initialize priv->plat->clk_csr with a non null value before read it in device tree (in stmmac_platform).

if (priv->plat->clk_csr >= 0)
priv->clk_csr = priv->plat->clk_csr;
else
stmmac_clk_csr_set(priv);



In some case, it's impossible to get the clk rate of stmmac_clk,
so it's better to remain the clk_csr flow.