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

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Message-ID: <8d0e4e2f-a131-ca19-e5ae-ef2349623b39@nvidia.com>
Date:   Wed, 29 Mar 2023 14:44:34 +0530
From:   Sumit Gupta <sumitg@...dia.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
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>,
        Sumit Gupta <sumitg@...dia.com>
Subject: Re: [Patch v4 10/10] PCI: tegra194: add interconnect support in
 Tegra234



On 28/03/23 23:23, Bjorn Helgaas wrote:
> External email: Use caution opening links or attachments
> 
> 
> 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.
> 
Ok, will swap.

>>   #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.
> 
Thank you for the review.
Will include the below change in the same patch. Please let me know if 
any issue.

  -       clk_set_rate(pcie->core_clk, pcie_gen_freq[speed - 1]);
  +       if (speed && (speed <= ARRAY_SIZE(pcie_gen_freq)))
  +               clk_set_rate(pcie->core_clk, pcie_gen_freq[speed - 1]);
  +       else
  +               clk_set_rate(pcie->core_clk, pcie_gen_freq[0]);

Thank you,
Sumit Gupta

>> +}
>> +
>>   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);