linux-kernel - Re: [Patch v4 10/10] PCI: tegra194: add interconnect support in Tegra234

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Date:   Tue, 28 Mar 2023 12:53:50 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Sumit Gupta <sumitg@...dia.com>
Cc:     treding@...dia.com, krzysztof.kozlowski@...aro.org,
        dmitry.osipenko@...labora.com, viresh.kumar@...aro.org,
        rafael@...nel.org, jonathanh@...dia.com, robh+dt@...nel.org,
        lpieralisi@...nel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-pci@...r.kernel.org,
        mmaddireddy@...dia.com, kw@...ux.com, bhelgaas@...gle.com,
        vidyas@...dia.com, sanjayc@...dia.com, ksitaraman@...dia.com,
        ishah@...dia.com, bbasu@...dia.com
Subject: Re: [Patch v4 10/10] PCI: tegra194: add interconnect support in
 Tegra234

Capitalize subject line please, to match pcie-tegra194.c history.

On Mon, Mar 27, 2023 at 09:44:26PM +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@...dia.com>
> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> ---
>  drivers/pci/controller/dwc/pcie-tegra194.c | 40 +++++++++++++++++-----
>  1 file changed, 32 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
> index 09825b4a075e..d2513c9d3feb 100644
> --- a/drivers/pci/controller/dwc/pcie-tegra194.c
> +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
> @@ -15,6 +15,7 @@
>  #include <linux/gpio.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/interrupt.h>
> +#include <linux/interconnect.h>

Almost alphabetized, swap interrupt.h and interconnect.h.

>  #include <linux/iopoll.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
> @@ -287,6 +288,7 @@ 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 +311,24 @@ 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);
> +
> +	clk_set_rate(pcie->core_clk, pcie_gen_freq[speed - 1]);

Array bounds violation; PCI_EXP_LNKSTA_CLS is 0x000f, so possible
speed (CLS) values are 0..0xf and "speed - 1" values are -1..0xe.

pcie_gen_freq[] is of size 4 (valid indices 0..3).

I see that you're just *moving* this code, but might as well fix it.

> +}
> +
>  static void apply_bad_link_workaround(struct dw_pcie_rp *pp)
>  {
>  	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
> @@ -452,14 +472,12 @@ 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);