Date:   Tue, 21 Mar 2017 15:08:16 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Joao Pinto <Joao.Pinto@...opsys.com>
Cc:     davem@...emloft.net, peppe.cavallaro@...com,
        alexandre.torgue@...com, niklas.cassel@...s.com,
        netdev@...r.kernel.org
Subject: Re: [v5,net-next,2/9] net: stmmac: configure mtl rx and tx algorithms

On Tue, Mar 21, 2017 at 01:58:36PM +0000, Joao Pinto wrote:
> Às 12:24 PM de 3/21/2017, Thierry Reding escreveu:
> > On Tue, Mar 21, 2017 at 12:02:03PM +0000, Joao Pinto wrote:
> >> Às 11:58 AM de 3/21/2017, Thierry Reding escreveu:
> >>> On Fri, Mar 10, 2017 at 06:24:52PM +0000, Joao Pinto wrote:
> >>>> This patch adds the RX and TX scheduling algorithms programming.
> >>>> It introduces the multiple queues configuration function
> >>>> (stmmac_mtl_configuration) in stmmac_main.
> >>>>
> >>>> Signed-off-by: Joao Pinto <jpinto@...opsys.com>
> >>>> ---
> >>>> Changes v4->v5:
> >>>> - patch title update (stmicro replaced by stmmac)
> >>>> Changes v3->v4:
> >>>> - Just to keep up with patch-set version
> >>>> Changes v2->v3:
> >>>> - Switch statements with a tab
> >>>> Changes v1->v2:
> >>>> - Just to keep up with patch-set version
> >>>>
> >>>>  drivers/net/ethernet/stmicro/stmmac/common.h      |  4 ++
> >>>>  drivers/net/ethernet/stmicro/stmmac/dwmac4.h      | 10 +++++
> >>>>  drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c | 48 +++++++++++++++++++++++
> >>>>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 31 +++++++++++++--
> >>>>  4 files changed, 90 insertions(+), 3 deletions(-)
> >>>
> >>> This patch breaks backwards-compatibility with DTBs that don't have an
> >>> of the multiple queue properties.
> >>>
> >>> See below...
> >>>
> >>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/common.h b/drivers/net/ethernet/stmicro/stmmac/common.h
> >>>> index 04d9245..5a0a781 100644
> >>>> --- a/drivers/net/ethernet/stmicro/stmmac/common.h
> >>>> +++ b/drivers/net/ethernet/stmicro/stmmac/common.h
> >>>> @@ -455,6 +455,10 @@ struct stmmac_ops {
> >>>>  	int (*rx_ipc)(struct mac_device_info *hw);
> >>>>  	/* Enable RX Queues */
> >>>>  	void (*rx_queue_enable)(struct mac_device_info *hw, u32 queue);
> >>>> +	/* Program RX Algorithms */
> >>>> +	void (*prog_mtl_rx_algorithms)(struct mac_device_info *hw, u32 rx_alg);
> >>>> +	/* Program TX Algorithms */
> >>>> +	void (*prog_mtl_tx_algorithms)(struct mac_device_info *hw, u32 tx_alg);
> >>>>  	/* Dump MAC registers */
> >>>>  	void (*dump_regs)(struct mac_device_info *hw, u32 *reg_space);
> >>>>  	/* Handle extra events on specific interrupts hw dependent */
> >>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
> >>>> index db45134..748ab6f 100644
> >>>> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
> >>>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4.h
> >>>> @@ -161,6 +161,16 @@ enum power_event {
> >>>>  #define GMAC_HI_REG_AE			BIT(31)
> >>>>  
> >>>>  /*  MTL registers */
> >>>> +#define MTL_OPERATION_MODE		0x00000c00
> >>>> +#define MTL_OPERATION_SCHALG_MASK	GENMASK(6, 5)
> >>>> +#define MTL_OPERATION_SCHALG_WRR	(0x0 << 5)
> >>>> +#define MTL_OPERATION_SCHALG_WFQ	(0x1 << 5)
> >>>> +#define MTL_OPERATION_SCHALG_DWRR	(0x2 << 5)
> >>>> +#define MTL_OPERATION_SCHALG_SP		(0x3 << 5)
> >>>> +#define MTL_OPERATION_RAA		BIT(2)
> >>>> +#define MTL_OPERATION_RAA_SP		(0x0 << 2)
> >>>> +#define MTL_OPERATION_RAA_WSP		(0x1 << 2)
> >>>> +
> >>>>  #define MTL_INT_STATUS			0x00000c20
> >>>>  #define MTL_INT_Q0			BIT(0)
> >>>>  
> >>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> >>>> index 1e79e65..f966755 100644
> >>>> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> >>>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c
> >>>> @@ -70,6 +70,52 @@ static void dwmac4_rx_queue_enable(struct mac_device_info *hw, u32 queue)
> >>>>  	writel(value, ioaddr + GMAC_RXQ_CTRL0);
> >>>>  }
> >>>>  
> >>>> +static void dwmac4_prog_mtl_rx_algorithms(struct mac_device_info *hw,
> >>>> +					  u32 rx_alg)
> >>>> +{
> >>>> +	void __iomem *ioaddr = hw->pcsr;
> >>>> +	u32 value = readl(ioaddr + MTL_OPERATION_MODE);
> >>>> +
> >>>> +	value &= ~MTL_OPERATION_RAA;
> >>>> +	switch (rx_alg) {
> >>>> +	case MTL_RX_ALGORITHM_SP:
> >>>> +		value |= MTL_OPERATION_RAA_SP;
> >>>> +		break;
> >>>> +	case MTL_RX_ALGORITHM_WSP:
> >>>> +		value |= MTL_OPERATION_RAA_WSP;
> >>>> +		break;
> >>>> +	default:
> >>>> +		break;
> >>>> +	}
> >>>> +
> >>>> +	writel(value, ioaddr + MTL_OPERATION_MODE);
> >>>> +}
> >>>> +
> >>>> +static void dwmac4_prog_mtl_tx_algorithms(struct mac_device_info *hw,
> >>>> +					  u32 tx_alg)
> >>>> +{
> >>>> +	void __iomem *ioaddr = hw->pcsr;
> >>>> +	u32 value = readl(ioaddr + MTL_OPERATION_MODE);
> >>>> +
> >>>> +	value &= ~MTL_OPERATION_SCHALG_MASK;
> >>>> +	switch (tx_alg) {
> >>>> +	case MTL_TX_ALGORITHM_WRR:
> >>>> +		value |= MTL_OPERATION_SCHALG_WRR;
> >>>> +		break;
> >>>> +	case MTL_TX_ALGORITHM_WFQ:
> >>>> +		value |= MTL_OPERATION_SCHALG_WFQ;
> >>>> +		break;
> >>>> +	case MTL_TX_ALGORITHM_DWRR:
> >>>> +		value |= MTL_OPERATION_SCHALG_DWRR;
> >>>> +		break;
> >>>> +	case MTL_TX_ALGORITHM_SP:
> >>>> +		value |= MTL_OPERATION_SCHALG_SP;
> >>>> +		break;
> >>>> +	default:
> >>>> +		break;
> >>>> +	}
> >>>> +}
> >>>> +
> >>>>  static void dwmac4_dump_regs(struct mac_device_info *hw, u32 *reg_space)
> >>>>  {
> >>>>  	void __iomem *ioaddr = hw->pcsr;
> >>>> @@ -457,6 +503,8 @@ static const struct stmmac_ops dwmac4_ops = {
> >>>>  	.core_init = dwmac4_core_init,
> >>>>  	.rx_ipc = dwmac4_rx_ipc_enable,
> >>>>  	.rx_queue_enable = dwmac4_rx_queue_enable,
> >>>> +	.prog_mtl_rx_algorithms = dwmac4_prog_mtl_rx_algorithms,
> >>>> +	.prog_mtl_tx_algorithms = dwmac4_prog_mtl_tx_algorithms,
> >>>>  	.dump_regs = dwmac4_dump_regs,
> >>>>  	.host_irq_status = dwmac4_irq_status,
> >>>>  	.flow_ctrl = dwmac4_flow_ctrl,
> >>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >>>> index 4498a38..af57f8d 100644
> >>>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >>>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> >>>> @@ -1645,6 +1645,31 @@ static void stmmac_init_tx_coalesce(struct stmmac_priv *priv)
> >>>>  }
> >>>>  
> >>>>  /**
> >>>> + *  stmmac_mtl_configuration - Configure MTL
> >>>> + *  @priv: driver private structure
> >>>> + *  Description: It is used for configurring MTL
> >>>> + */
> >>>> +static void stmmac_mtl_configuration(struct stmmac_priv *priv)
> >>>> +{
> >>>> +	u32 rx_queues_count = priv->plat->rx_queues_to_use;
> >>>> +	u32 tx_queues_count = priv->plat->tx_queues_to_use;
> >>>> +
> >>>> +	/* Configure MTL RX algorithms */
> >>>> +	if (rx_queues_count > 1 && priv->hw->mac->prog_mtl_rx_algorithms)
> >>>> +		priv->hw->mac->prog_mtl_rx_algorithms(priv->hw,
> >>>> +						priv->plat->rx_sched_algorithm);
> >>>> +
> >>>> +	/* Configure MTL TX algorithms */
> >>>> +	if (tx_queues_count > 1 && priv->hw->mac->prog_mtl_tx_algorithms)
> >>>> +		priv->hw->mac->prog_mtl_tx_algorithms(priv->hw,
> >>>> +						priv->plat->tx_sched_algorithm);
> >>>> +
> >>>> +	/* Enable MAC RX Queues */
> >>>> +	if (rx_queues_count > 1 && priv->hw->mac->rx_queue_enable)
> >>>> +		stmmac_mac_enable_rx_queues(priv);
> >>>
> >>> This is almost equivalent to the code removed from stmmac_hw_setup()
> >>> which happens to be the key for this driver to work for me. However, the
> >>> code above adds an additional check for rx_queues_count > 1 which is
> >>> going to be false for any existing DTB, because it is derived from the
> >>> values retrieved from new device tree properties.
> >>>
> >>> So I think for backwards compatibility we'd need something like this:
> >>>
> >>> 	if ((rx_queue_count == 0 || rx_queue_count > 1) &&
> >>> 	    priv->hw->mac->rx_queue_enable)
> >>>
> >>> But then I'm beginning to think maybe we don't need a check here at all
> >>> because it would only prevent RX queue setup for rx_queue_count == 1 and
> >>> I think it would still be legitimate to set it up even then.
> >>>
> >>> stmmac_mac_enable_rx_queues() already checks for rx_count == 1, but that
> >>> is derived from the number of RX queues derived from the feature
> >>> registers and therefore refers to the number of queues that the hardware
> >>> supports as opposed to the number of queues configured in device tree.
> >>>
> >>> I can follow up with a patch to restore backwards-compatibility.
> >>
> >> Forhw configured as single queue you don't need to enable the rx queue, since
> >> they are enable by default. if you check in stmmac_platform.c I assure backward
> >> compatibility by setting the number of rx and tx queues = 1 if nothing is
> >> declared. Please check here:
> >>
> >> https://urldefense.proofpoint.com/v2/url?u=https-3A__git.kernel.org_pub_scm_linux_kernel_git_davem_net-2Dnext.git_tree_drivers_net_ethernet_stmicro_stmmac_stmmac-5Fplatform.c-23n156&d=DwIFaQ&c=DPL6_X_6JkXFx7AXWqB0tg&r=s2fO0hii0OGNOv9qQy_HRXy-xAJUD1NNoEcc3io_kx0&m=tvYpf8cZr-Y6Zl-d7NlT2FEW7Gv5Bzs86GMIhZs4OSI&s=jA0P7-MXCVOtu262fF75EhUq5dfcDutzsYg8CAE6XQc&e= 
> > 
> > Ah yes, I just ran across that trying to debug why a subsequent patch
> > broke things again. I think the rx_queue_count > 1 condition is still
> > wrong in the above because it will still fail for the backwards-
> > compatibility case.
> 
> Enabling RX Queue is needed only if the hw is configured as having more than 1
> RX queue. If your hardware is configured as being multiple-queue,
> rx_queue_to_use should be > 1. True single queue hardware will work fine.

But that's certainly not the case right now. The rx_queues_to_use field
is initialized based on the new snps,rx-queues-to-use device tree
property, or initialized to 1 in the absence of that property (and for
PCI). Effectively that means all users of this driver will have their
rx_queues_to_use field set to 1 until the DTS files are updated to set
some other value. But that's not a requirement that we can impose. We
still need to be able to deal with old device trees without regression.

Even without the backwards-compatibility argument, wouldn't it make
sense to allow users to restrict usage to a single RX queue even on
hardware that supports multiple ones? It certainly works fine in my
case, I don't see any advantage in forbidding it.

Thierry

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