Re: [PATCH] net: ethernet: stmmac: properly set PS bit in MII configurations during reset

[Giuseppe CAVALLARO <peppe.cavallaro@xxxxxx>]

Hello Thomas

this was initially set by using the hw->link.port; both the core_init 
and adjust callback
should invoke the hook and tuning the PS bit according to the speed and 
mode.
So maybe the ->set_ps is superfluous and you could reuse the existent hook

let me know

Regards
peppe

On 4/27/2017 11:45 AM, Thomas Petazzoni wrote:
> On the SPEAr600 SoC, which has the dwmac1000 variant of the IP block,
> the DMA reset never succeeds when a MII PHY is used (no problem with a
> GMII PHY). The dwmac_dma_reset() function sets the
> DMA_BUS_MODE_SFT_RESET bit in the DMA_BUS_MODE register, and then
> polls until this bit clears. When a MII PHY is used, with the current
> driver, this bit never clears and the driver therefore doesn't work.
>
> The reason is that the PS bit of the GMAC_CONTROL register should be
> correctly configured for the DMA reset to work. When the PS bit is 0,
> it tells the MAC we have a GMII PHY, when the PS bit is 1, it tells
> the MAC we have a MII PHY.
>
> Doing a DMA reset clears all registers, so the PS bit is cleared as
> well. This makes the DMA reset work fine with a GMII PHY. However,
> with MII PHY, the PS bit should be set.
>
> We have identified this issue thanks to two SPEAr600 platform:
>
>   - One equipped with a GMII PHY, with which the existing driver was
>     working fine.
>
>   - One equipped with a MII PHY, where the current driver fails because
>     the DMA reset times out.
>
> This patch fixes the problem for the MII PHY configuration, and has
> been tested with a GMII PHY configuration as well.
>
> In terms of implement, since the ->reset() hook is implemented in the
> DMA related code, we do not want to touch directly from this function
> the MAC registers. Therefore, a ->set_ps() hook has been added to
> stmmac_ops, which gets called between the moment the reset is asserted
> and the polling loop waiting for the reset bit to clear.
>
> In order for this ->set_ps() hook to decide what to do, we pass it the
> "struct mac_device_info" so it can access the MAC registers, and the
> PHY interface type so it knows if we're using a MII PHY or not.
>
> The ->set_ps() hook is only implemented for the dwmac1000 case.
>
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> ---
> Do not hesitate to suggest ideas for alternative implementations, I'm
> not sure if the current proposal is the one that fits best with the
> current design of the driver.
> ---
>   drivers/net/ethernet/stmicro/stmmac/common.h         | 12 +++++++++---
>   drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c | 16 ++++++++++++++++
>   drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h     |  3 ++-
>   drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c     |  7 ++++++-
>   drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h      |  3 ++-
>   drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c      |  6 +++++-
>   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c    |  3 ++-
>   7 files changed, 42 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
> index 04d9245..d576f95 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/common.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/common.h
> @@ -407,10 +407,13 @@ struct stmmac_desc_ops {
>   extern const struct stmmac_desc_ops enh_desc_ops;
>   extern const struct stmmac_desc_ops ndesc_ops;
>   
> +struct mac_device_info;
> +
>   /* Specific DMA helpers */
>   struct stmmac_dma_ops {
>   	/* DMA core initialization */
> -	int (*reset)(void __iomem *ioaddr);
> +	int (*reset)(void __iomem *ioaddr, struct mac_device_info *hw,
> +		     phy_interface_t interface);
>   	void (*init)(void __iomem *ioaddr, struct stmmac_dma_cfg *dma_cfg,
>   		     u32 dma_tx, u32 dma_rx, int atds);
>   	/* Configure the AXI Bus Mode Register */
> @@ -445,12 +448,15 @@ struct stmmac_dma_ops {
>   	void (*enable_tso)(void __iomem *ioaddr, bool en, u32 chan);
>   };
>   
> -struct mac_device_info;
> -
>   /* Helpers to program the MAC core */
>   struct stmmac_ops {
>   	/* MAC core initialization */
>   	void (*core_init)(struct mac_device_info *hw, int mtu);
> +	/* Set port select. Called between asserting DMA reset and
> +	 * waiting for the reset bit to clear.
> +	 */
> +	void (*set_ps)(struct mac_device_info *hw,
> +		       phy_interface_t interface);
>   	/* Enable and verify that the IPC module is supported */
>   	int (*rx_ipc)(struct mac_device_info *hw);
>   	/* Enable RX Queues */
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c
> index 19b9b308..dfcbb5b 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c
> @@ -75,6 +75,21 @@ static void dwmac1000_core_init(struct mac_device_info *hw, int mtu)
>   #endif
>   }
>   
> +static void dwmac1000_set_ps(struct mac_device_info *hw,
> +			     phy_interface_t interface)
> +{
> +	void __iomem *ioaddr = hw->pcsr;
> +	u32 value = readl(ioaddr + GMAC_CONTROL);
> +
> +	/* When a MII PHY is used, we must set the PS bit for the DMA
> +	 * reset to succeed.
> +	 */
> +	if (interface == PHY_INTERFACE_MODE_MII)
> +		value |= GMAC_CONTROL_PS;
> +
> +	writel(value, ioaddr + GMAC_CONTROL);
> +}
> +
>   static int dwmac1000_rx_ipc_enable(struct mac_device_info *hw)
>   {
>   	void __iomem *ioaddr = hw->pcsr;
> @@ -488,6 +503,7 @@ static void dwmac1000_debug(void __iomem *ioaddr, struct stmmac_extra_stats *x)
>   
>   static const struct stmmac_ops dwmac1000_ops = {
>   	.core_init = dwmac1000_core_init,
> +	.set_ps = dwmac1000_set_ps,
>   	.rx_ipc = dwmac1000_rx_ipc_enable,
>   	.dump_regs = dwmac1000_dump_regs,
>   	.host_irq_status = dwmac1000_irq_status,
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h
> index 1b06df7..e9c6c49 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.h
> @@ -183,7 +183,8 @@
>   #define DMA_CHAN0_DBG_STAT_RPS		GENMASK(11, 8)
>   #define DMA_CHAN0_DBG_STAT_RPS_SHIFT	8
>   
> -int dwmac4_dma_reset(void __iomem *ioaddr);
> +int dwmac4_dma_reset(void __iomem *ioaddr, struct mac_device_info *hw,
> +		     phy_interface_t interface);
>   void dwmac4_enable_dma_transmission(void __iomem *ioaddr, u32 tail_ptr);
>   void dwmac4_enable_dma_irq(void __iomem *ioaddr);
>   void dwmac410_enable_dma_irq(void __iomem *ioaddr);
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
> index c7326d5..485eecb 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
> @@ -14,7 +14,8 @@
>   #include "dwmac4_dma.h"
>   #include "dwmac4.h"
>   
> -int dwmac4_dma_reset(void __iomem *ioaddr)
> +int dwmac4_dma_reset(void __iomem *ioaddr, struct mac_device_info *hw,
> +		     phy_interface_t interface)
>   {
>   	u32 value = readl(ioaddr + DMA_BUS_MODE);
>   	int limit;
> @@ -22,6 +23,10 @@ int dwmac4_dma_reset(void __iomem *ioaddr)
>   	/* DMA SW reset */
>   	value |= DMA_BUS_MODE_SFT_RESET;
>   	writel(value, ioaddr + DMA_BUS_MODE);
> +
> +	if (hw->mac->set_ps)
> +		hw->mac->set_ps(hw, interface);
> +
>   	limit = 10;
>   	while (limit--) {
>   		if (!(readl(ioaddr + DMA_BUS_MODE) & DMA_BUS_MODE_SFT_RESET))
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h b/drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h
> index 56e485f..25ae028 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac_dma.h
> @@ -144,6 +144,7 @@ void dwmac_dma_stop_tx(void __iomem *ioaddr);
>   void dwmac_dma_start_rx(void __iomem *ioaddr);
>   void dwmac_dma_stop_rx(void __iomem *ioaddr);
>   int dwmac_dma_interrupt(void __iomem *ioaddr, struct stmmac_extra_stats *x);
> -int dwmac_dma_reset(void __iomem *ioaddr);
> +int dwmac_dma_reset(void __iomem *ioaddr, struct mac_device_info *hw,
> +		    phy_interface_t interface);
>   
>   #endif /* __DWMAC_DMA_H__ */
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c b/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c
> index e60bfca..1a17df5 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac_lib.c
> @@ -23,7 +23,8 @@
>   
>   #define GMAC_HI_REG_AE		0x80000000
>   
> -int dwmac_dma_reset(void __iomem *ioaddr)
> +int dwmac_dma_reset(void __iomem *ioaddr, struct mac_device_info *hw,
> +		    phy_interface_t interface)
>   {
>   	u32 value = readl(ioaddr + DMA_BUS_MODE);
>   	int err;
> @@ -32,6 +33,9 @@ int dwmac_dma_reset(void __iomem *ioaddr)
>   	value |= DMA_BUS_MODE_SFT_RESET;
>   	writel(value, ioaddr + DMA_BUS_MODE);
>   
> +	if (hw->mac->set_ps)
> +		hw->mac->set_ps(hw, interface);
> +
>   	err = readl_poll_timeout(ioaddr + DMA_BUS_MODE, value,
>   				 !(value & DMA_BUS_MODE_SFT_RESET),
>   				 100000, 10000);
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 4498a38..66bc218 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -1585,7 +1585,8 @@ static int stmmac_init_dma_engine(struct stmmac_priv *priv)
>   	if (priv->extend_desc && (priv->mode == STMMAC_RING_MODE))
>   		atds = 1;
>   
> -	ret = priv->hw->dma->reset(priv->ioaddr);
> +	ret = priv->hw->dma->reset(priv->ioaddr, priv->hw,
> +				   priv->plat->interface);
>   	if (ret) {
>   		dev_err(priv->device, "Failed to reset the dma\n");
>   		return ret;