Re: [PATCH v3 10/12] PCI: rockchip-ep: Improve link training

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Mon, Oct 07, 2024 at 01:12:16PM +0900, Damien Le Moal wrote:
> The Rockchip rk339 technical reference manual describe the endpoint mode

RK3399

Please include the full reference: TRM name followed by the section.

> link training process clearly and states that:
>   Insure link training completion and success by observing link_st field
>   in PCIe Client BASIC_STATUS1 register change to 2'b11. If both side
>   support PCIe Gen2 speed, re-train can be Initiated by asserting the
>   Retrain Link field in Link Control and Status Register. The software
>   should insure the BASIC_STATUS0[negotiated_speed] changes to "1", that
>   indicates re-train to Gen2 successfully.
> This procedure is very similar to what is done for the root-port mode in
> rockchip_pcie_host_init_port().
> 
> Implement this link training procedure for the endpoint mode as well.
> Given that the rk3399 SoC does not have an interrupt signaling link
> status changes, training is implemented as a delayed work which is
> rescheduled until the link training completes or the endpoint controller
> is stopped. The link training work is first scheduled in
> rockchip_pcie_ep_start() when the endpoint function is started. Link
> training completion is signaled to the function using pci_epc_linkup().
> Accordingly, the linkup_notifier field of the rockchip pci_epc_features
> structure is changed to true.
> 
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>  drivers/pci/controller/pcie-rockchip-ep.c | 79 ++++++++++++++++++++++-
>  drivers/pci/controller/pcie-rockchip.h    | 11 ++++
>  2 files changed, 89 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
> index a801e040bcad..af50432525b4 100644
> --- a/drivers/pci/controller/pcie-rockchip-ep.c
> +++ b/drivers/pci/controller/pcie-rockchip-ep.c
> @@ -16,6 +16,8 @@
>  #include <linux/platform_device.h>
>  #include <linux/pci-epf.h>
>  #include <linux/sizes.h>
> +#include <linux/workqueue.h>
> +#include <linux/iopoll.h>

Please keep the includes sorted.

>  
>  #include "pcie-rockchip.h"
>  
> @@ -48,6 +50,7 @@ struct rockchip_pcie_ep {
>  	u64			irq_pci_addr;
>  	u8			irq_pci_fn;
>  	u8			irq_pending;
> +	struct delayed_work	link_training;
>  };
>  
>  static void rockchip_pcie_clear_ep_ob_atu(struct rockchip_pcie *rockchip,
> @@ -465,6 +468,8 @@ static int rockchip_pcie_ep_start(struct pci_epc *epc)
>  			    PCIE_CLIENT_CONF_ENABLE,
>  			    PCIE_CLIENT_CONFIG);
>  
> +	schedule_delayed_work(&ep->link_training, 0);
> +
>  	return 0;
>  }
>  
> @@ -473,6 +478,8 @@ static void rockchip_pcie_ep_stop(struct pci_epc *epc)
>  	struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
>  	struct rockchip_pcie *rockchip = &ep->rockchip;
>  
> +	cancel_delayed_work_sync(&ep->link_training);
> +
>  	/* Stop link training and disable configuration */
>  	rockchip_pcie_write(rockchip,
>  			    PCIE_CLIENT_CONF_DISABLE |
> @@ -480,8 +487,77 @@ static void rockchip_pcie_ep_stop(struct pci_epc *epc)
>  			    PCIE_CLIENT_CONFIG);
>  }
>  
> +static void rockchip_pcie_ep_retrain_link(struct rockchip_pcie *rockchip)
> +{
> +	u32 status;
> +
> +	status = rockchip_pcie_read(rockchip, PCIE_EP_CONFIG_LCS);
> +	status |= PCI_EXP_LNKCTL_RL;
> +	rockchip_pcie_write(rockchip, status, PCIE_EP_CONFIG_LCS);
> +}
> +
> +static bool rockchip_pcie_ep_link_up(struct rockchip_pcie *rockchip)
> +{
> +	u32 val = rockchip_pcie_read(rockchip, PCIE_CLIENT_BASIC_STATUS1);
> +
> +	return PCIE_LINK_UP(val);
> +}
> +
> +static void rockchip_pcie_ep_link_training(struct work_struct *work)
> +{
> +	struct rockchip_pcie_ep *ep =
> +		container_of(work, struct rockchip_pcie_ep, link_training.work);
> +	struct rockchip_pcie *rockchip = &ep->rockchip;
> +	struct device *dev = rockchip->dev;
> +	u32 val;
> +	int ret;
> +
> +	/* Enable Gen1 training and wait for its completion */
> +	ret = readl_poll_timeout(rockchip->apb_base + PCIE_CORE_CTRL,
> +				 val, PCIE_LINK_TRAINING_DONE(val), 50,
> +				 LINK_TRAIN_TIMEOUT);
> +	if (ret)
> +		goto again;
> +
> +	/* Make sure that the link is up */
> +	ret = readl_poll_timeout(rockchip->apb_base + PCIE_CLIENT_BASIC_STATUS1,
> +				 val, PCIE_LINK_UP(val), 50,
> +				 LINK_TRAIN_TIMEOUT);
> +	if (ret)
> +		goto again;
> +
> +	/* Check the current speed */
> +	val = rockchip_pcie_read(rockchip, PCIE_CORE_CTRL);
> +	if (!PCIE_LINK_IS_GEN2(val) && rockchip->link_gen == 2) {

PCIE_LINK_IS_GEN2()?

> +		/* Enable retrain for gen2 */
> +		rockchip_pcie_ep_retrain_link(rockchip);
> +		readl_poll_timeout(rockchip->apb_base + PCIE_CORE_CTRL,
> +				   val, PCIE_LINK_IS_GEN2(val), 50,
> +				   LINK_TRAIN_TIMEOUT);
> +	}
> +
> +	/* Check again that the link is up */
> +	if (!rockchip_pcie_ep_link_up(rockchip))
> +		goto again;

TRM doesn't mention this check. Is this really necessary?

> +
> +	val = rockchip_pcie_read(rockchip, PCIE_CLIENT_BASIC_STATUS0);
> +	dev_info(dev,
> +		 "Link UP (Negociated speed: %sGT/s, width: x%lu)\n",


Negotiated

> +		 (val & PCIE_CLIENT_NEG_LINK_SPEED) ? "5" : "2.5",
> +		 ((val & PCIE_CLIENT_NEG_LINK_WIDTH_MASK) >>
> +		  PCIE_CLIENT_NEG_LINK_WIDTH_SHIFT) << 1);
> +
> +	/* Notify the function */
> +	pci_epc_linkup(ep->epc);
> +
> +	return;
> +
> +again:
> +	schedule_delayed_work(&ep->link_training, msecs_to_jiffies(5));
> +}
> +
>  static const struct pci_epc_features rockchip_pcie_epc_features = {
> -	.linkup_notifier = false,
> +	.linkup_notifier = true,
>  	.msi_capable = true,
>  	.msix_capable = false,
>  	.align = ROCKCHIP_PCIE_AT_SIZE_ALIGN,
> @@ -642,6 +718,7 @@ static int rockchip_pcie_ep_probe(struct platform_device *pdev)
>  	rockchip = &ep->rockchip;
>  	rockchip->is_rc = false;
>  	rockchip->dev = dev;
> +	INIT_DELAYED_WORK(&ep->link_training, rockchip_pcie_ep_link_training);
>  
>  	epc = devm_pci_epc_create(dev, &rockchip_pcie_epc_ops);
>  	if (IS_ERR(epc)) {
> diff --git a/drivers/pci/controller/pcie-rockchip.h b/drivers/pci/controller/pcie-rockchip.h
> index 0263f158ee8d..3963b7097a91 100644
> --- a/drivers/pci/controller/pcie-rockchip.h
> +++ b/drivers/pci/controller/pcie-rockchip.h
> @@ -26,6 +26,7 @@
>  #define MAX_LANE_NUM			4
>  #define MAX_REGION_LIMIT		32
>  #define MIN_EP_APERTURE			28
> +#define LINK_TRAIN_TIMEOUT		(5000 * USEC_PER_MSEC)

pcie-rockchip-host has only 500ms timeout.

- Mani

-- 
மணிவண்ணன் சதாசிவம்