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

From: Sumit Gupta <sumitg@nvidia.com>
To: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: <treding@nvidia.com>, <krzysztof.kozlowski@linaro.org>,
	<dmitry.osipenko@collabora.com>, <viresh.kumar@linaro.org>,
	<rafael@kernel.org>, <jonathanh@nvidia.com>, <robh+dt@kernel.org>,
	<helgaas@kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-tegra@vger.kernel.org>, <linux-pm@vger.kernel.org>,
	<devicetree@vger.kernel.org>, <linux-pci@vger.kernel.org>,
	<mmaddireddy@nvidia.com>, <kw@linux.com>, <bhelgaas@google.com>,
	<vidyas@nvidia.com>, <sanjayc@nvidia.com>,
	<ksitaraman@nvidia.com>, <ishah@nvidia.com>, <bbasu@nvidia.com>,
	Sumit Gupta <sumitg@nvidia.com>
Subject: Re: [Patch v5 7/8] PCI: tegra194: add interconnect support in Tegra234
Date: Thu, 6 Apr 2023 17:43:55 +0530	[thread overview]
Message-ID: <141f83be-e08b-9c0b-8939-554e3d5ed37d@nvidia.com> (raw)
In-Reply-To: <ZC1Rnrb0MObR5S42@lpieralisi>

> 
> You should still capitalize the subject.
> 
> "PCI: tegra194: Add interconnect.."
> 
Sure.

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

> 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
> 
Thank you for the review.
I will split this patch into two and add the info as sugested in v6.

Will spin a v6 soon if there is no further comment.

Thanks,
Sumit

>> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
>> ---
>>   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
>>