Re: [Patch v5 7/8] PCI: tegra194: add interconnect support in Tegra234

[Lorenzo Pieralisi]

You should still capitalize the subject.

"PCI: tegra194: Add interconnect.."

On Thu, Mar 30, 2023 at 07:03:53PM +0530, Sumit Gupta wrote:
> Add support to request DRAM bandwidth with Memory Interconnect
> in Tegra234 SoC. The DRAM BW required for different modes depends
> on speed (Gen-1/2/3/4) and width/lanes (x1/x2/x4/x8).
> 
> Suggested-by: Manikanta Maddireddy <mmaddireddy@xxxxxxxxxx>

You should add a Link to the relevant lore archive, I am
pretty sure Bjorn chimed in too.

This patch does too many things at once; more importantly it
does *not* explain why we request memory bandwidth and why it
is required and *safe* given that the current code works so far.

So:

patch 1: fix the array overflow issues with the current code
patch 2: add memory bandwidth interconnect support

Thanks,
Lorenzo

> Signed-off-by: Sumit Gupta <sumitg@xxxxxxxxxx>
> ---
>  drivers/pci/controller/dwc/pcie-tegra194.c | 44 ++++++++++++++++++----
>  1 file changed, 36 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
> index 09825b4a075e..89d829a946ee 100644
> --- a/drivers/pci/controller/dwc/pcie-tegra194.c
> +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
> @@ -14,6 +14,7 @@
>  #include <linux/delay.h>
>  #include <linux/gpio.h>
>  #include <linux/gpio/consumer.h>
> +#include <linux/interconnect.h>
>  #include <linux/interrupt.h>
>  #include <linux/iopoll.h>
>  #include <linux/kernel.h>
> @@ -223,6 +224,7 @@
>  #define EP_STATE_ENABLED	1
>  
>  static const unsigned int pcie_gen_freq[] = {
> +	GEN1_CORE_CLK_FREQ,   /* PCI_EXP_LNKSTA_CLS == 0; undefined */
>  	GEN1_CORE_CLK_FREQ,
>  	GEN2_CORE_CLK_FREQ,
>  	GEN3_CORE_CLK_FREQ,
> @@ -287,6 +289,7 @@ struct tegra_pcie_dw {
>  	unsigned int pex_rst_irq;
>  	int ep_state;
>  	long link_status;
> +	struct icc_path *icc_path;
>  };
>  
>  static inline struct tegra_pcie_dw *to_tegra_pcie(struct dw_pcie *pci)
> @@ -309,6 +312,27 @@ struct tegra_pcie_soc {
>  	enum dw_pcie_device_mode mode;
>  };
>  
> +static void tegra_pcie_icc_set(struct tegra_pcie_dw *pcie)
> +{
> +	struct dw_pcie *pci = &pcie->pci;
> +	u32 val, speed, width;
> +
> +	val = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA);
> +
> +	speed = FIELD_GET(PCI_EXP_LNKSTA_CLS, val);
> +	width = FIELD_GET(PCI_EXP_LNKSTA_NLW, val);
> +
> +	val = width * (PCIE_SPEED2MBS_ENC(pcie_link_speed[speed]) / BITS_PER_BYTE);
> +
> +	if (icc_set_bw(pcie->icc_path, MBps_to_icc(val), 0))
> +		dev_err(pcie->dev, "can't set bw[%u]\n", val);
> +
> +	if (speed >= ARRAY_SIZE(pcie_gen_freq))
> +		speed = 0;
> +
> +	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed]);
> +}
> +
>  static void apply_bad_link_workaround(struct dw_pcie_rp *pp)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> @@ -452,14 +476,12 @@ static irqreturn_t tegra_pcie_ep_irq_thread(int irq, void *arg)
>  	struct tegra_pcie_dw *pcie = arg;
>  	struct dw_pcie_ep *ep = &pcie->pci.ep;
>  	struct dw_pcie *pci = &pcie->pci;
> -	u32 val, speed;
> +	u32 val;
>  
>  	if (test_and_clear_bit(0, &pcie->link_status))
>  		dw_pcie_ep_linkup(ep);
>  
> -	speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
> -		PCI_EXP_LNKSTA_CLS;
> -	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed - 1]);
> +	tegra_pcie_icc_set(pcie);
>  
>  	if (pcie->of_data->has_ltr_req_fix)
>  		return IRQ_HANDLED;
> @@ -945,9 +967,9 @@ static int tegra_pcie_dw_host_init(struct dw_pcie_rp *pp)
>  
>  static int tegra_pcie_dw_start_link(struct dw_pcie *pci)
>  {
> -	u32 val, offset, speed, tmp;
>  	struct tegra_pcie_dw *pcie = to_tegra_pcie(pci);
>  	struct dw_pcie_rp *pp = &pci->pp;
> +	u32 val, offset, tmp;
>  	bool retry = true;
>  
>  	if (pcie->of_data->mode == DW_PCIE_EP_TYPE) {
> @@ -1018,9 +1040,7 @@ static int tegra_pcie_dw_start_link(struct dw_pcie *pci)
>  		goto retry_link;
>  	}
>  
> -	speed = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA) &
> -		PCI_EXP_LNKSTA_CLS;
> -	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed - 1]);
> +	tegra_pcie_icc_set(pcie);
>  
>  	tegra_pcie_enable_interrupts(pp);
>  
> @@ -2224,6 +2244,14 @@ static int tegra_pcie_dw_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, pcie);
>  
> +	pcie->icc_path = devm_of_icc_get(&pdev->dev, "write");
> +	ret = PTR_ERR_OR_ZERO(pcie->icc_path);
> +	if (ret) {
> +		tegra_bpmp_put(pcie->bpmp);
> +		dev_err_probe(&pdev->dev, ret, "failed to get write interconnect\n");
> +		return ret;
> +	}
> +
>  	switch (pcie->of_data->mode) {
>  	case DW_PCIE_RC_TYPE:
>  		ret = devm_request_irq(dev, pp->irq, tegra_pcie_rp_irq_handler,
> -- 
> 2.17.1
>