[PATCH] net: stmmac: dwmac-qcom-ethqos: Enable RGMII functional clock on resume

[PATCH] net: stmmac: dwmac-qcom-ethqos: Enable RGMII functional clock on resume

[Bjorn Andersson]

When the Qualcomm ethqos driver is properly described in its associated
GDSC power-domain, the hardware will be powered down and loose its state
between qcom_ethqos_probe() and stmmac_init_dma_engine().

The result of this is that the functional clock from the RGMII IO macro
is no longer provides and the DMA software reset in dwmac4_dma_reset()
will time out, due to lacking clock signal.

Re-enable the functional clock, as part of the Qualcomm specific clock
enablement sequence to avoid this problem.

The final clock configuration will be adjusted by ethqos_fix_mac_speed()
once the link is being brought up.

Fixes: a7c30e62d4b8 ("net: stmmac: Add driver for Qualcomm ethqos")
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
index 0cc28c79cc61..835caa15d55f 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
@@ -487,6 +487,13 @@ static int ethqos_clks_config(void *priv, bool enabled)
 			dev_err(&ethqos->pdev->dev, "rgmii_clk enable failed\n");
 			return ret;
 		}
+
+		/* Enable functional clock to prevent DMA reset to timeout due
+		 * to lacking PHY clock after the hardware block has been power
+		 * cycled. The actual configuration will be adjusted once
+		 * ethqos_fix_mac_speed() is invoked.
+		 */
+		ethqos_set_func_clk_en(ethqos);
 	} else {
 		clk_disable_unprepare(ethqos->rgmii_clk);
 	}
-- 
2.33.1

Re: [PATCH] net: stmmac: dwmac-qcom-ethqos: Enable RGMII functional clock on resume

[Bhupesh Sharma]

+Cc: stable tree as I think this is an important fix for stmmac
dwmac-qcom-ethernet driver and affects ethernet functionality on QCOM
boards which use this driver.

More below..

On Wed, 23 Mar 2022 at 09:01, Bjorn Andersson
<bjorn.andersson@linaro.org> wrote:
>
> When the Qualcomm ethqos driver is properly described in its associated
> GDSC power-domain, the hardware will be powered down and loose its state
> between qcom_ethqos_probe() and stmmac_init_dma_engine().
>
> The result of this is that the functional clock from the RGMII IO macro
> is no longer provides and the DMA software reset in dwmac4_dma_reset()
> will time out, due to lacking clock signal.
>
> Re-enable the functional clock, as part of the Qualcomm specific clock
> enablement sequence to avoid this problem.
>
> The final clock configuration will be adjusted by ethqos_fix_mac_speed()
> once the link is being brought up.
>
> Fixes: a7c30e62d4b8 ("net: stmmac: Add driver for Qualcomm ethqos")
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c | 7 +++++++
>  1 file changed, 7 insertions(+)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
> index 0cc28c79cc61..835caa15d55f 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c
> @@ -487,6 +487,13 @@ static int ethqos_clks_config(void *priv, bool enabled)
>                         dev_err(&ethqos->pdev->dev, "rgmii_clk enable failed\n");
>                         return ret;
>                 }
> +
> +               /* Enable functional clock to prevent DMA reset to timeout due
> +                * to lacking PHY clock after the hardware block has been power
> +                * cycled. The actual configuration will be adjusted once
> +                * ethqos_fix_mac_speed() is invoked.
> +                */
> +               ethqos_set_func_clk_en(ethqos);
>         } else {
>                 clk_disable_unprepare(ethqos->rgmii_clk);
>         }
> --
> 2.33.1

Thanks for the catch, Bjorn. I tested this on the SA8155p-ADP board
and the eth interface can be moved from 'on' to 'off' state and
vice-versa properly after this change and we no longer need the EMAC
GDSC quirk, so:

Tested-and-Reviewed-by: Bhupesh Sharma <bhupesh.sharma@linaro.org>

Regards.

Re: [PATCH] net: stmmac: dwmac-qcom-ethqos: Enable RGMII functional clock on resume

[Greg Kroah-Hartman]

On Thu, Mar 24, 2022 at 03:08:08PM +0530, Bhupesh Sharma wrote:
> +Cc: stable tree as I think this is an important fix for stmmac
> dwmac-qcom-ethernet driver and affects ethernet functionality on QCOM
> boards which use this driver.

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

Re: [PATCH] net: stmmac: dwmac-qcom-ethqos: Enable RGMII functional clock on resume

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Tue, 22 Mar 2022 20:32:55 -0700 you wrote:
> When the Qualcomm ethqos driver is properly described in its associated
> GDSC power-domain, the hardware will be powered down and loose its state
> between qcom_ethqos_probe() and stmmac_init_dma_engine().
> 
> The result of this is that the functional clock from the RGMII IO macro
> is no longer provides and the DMA software reset in dwmac4_dma_reset()
> will time out, due to lacking clock signal.
> 
> [...]

Here is the summary with links:
  - net: stmmac: dwmac-qcom-ethqos: Enable RGMII functional clock on resume
    https://git.kernel.org/netdev/net/c/ffba2123e171

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html