linux-kernel - Re: [PATCH 2/7] PCI: dwc: Use FIELD

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Message-ID: <3o4neokfqofk42zrx5t5su72qmdu2x62rq5u2ywfobqyyg23rc@aksd3afajhwr>
Date:   Wed, 18 Oct 2023 14:58:46 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH 2/7] PCI: dwc: Use FIELD_GET/PREP()

On Wed, Oct 18, 2023 at 02:32:49PM +0300, Ilpo Järvinen wrote:
> Convert open-coded variants of PCI field access into FIELD_GET/PREP()
> to make the code easier to understand.
> 
> Add two missing defines into pci_regs.h. Logically, the Max No-Snoop
> Latency Register is a separate word sized register in the PCIe spec,
> but the pre-existing LTR defines in pci_regs.h with dword long values
> seem to consider the registers together (the same goes for the only
> user). Thus, follow the custom and make the new values also take both
> word long LTR registers as a joint dword register.

Nice work. Thanks! Could you also have a look at
drivers/pci/controller/dwc/pcie-designware.c
?
It contains two open-coded patterns:
(bar << 8) - FIELD_PREP()
next_cap_ptr = (reg & 0xff00) >> 8; - FIELD_GET().
next_cap_ptr = (reg & 0x00ff); - FIELD_GET().
At least the later two statements concern the generic PCIe capability CSR.

-Serge(y)


> 
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware-ep.c | 7 ++++---
>  drivers/pci/controller/dwc/pcie-tegra194.c      | 5 ++---
>  include/uapi/linux/pci_regs.h                   | 2 ++
>  3 files changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> index f9182f8d552f..20bef1436bfb 100644
> --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> @@ -6,6 +6,7 @@
>   * Author: Kishon Vijay Abraham I <kishon@...com>
>   */
>  
> +#include <linux/bitfield.h>
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
>  
> @@ -334,7 +335,7 @@ static int dw_pcie_ep_get_msi(struct pci_epc *epc, u8 func_no, u8 vfunc_no)
>  	if (!(val & PCI_MSI_FLAGS_ENABLE))
>  		return -EINVAL;
>  
> -	val = (val & PCI_MSI_FLAGS_QSIZE) >> 4;
> +	val = FIELD_GET(PCI_MSI_FLAGS_QSIZE, val);
>  
>  	return val;
>  }
> @@ -357,7 +358,7 @@ static int dw_pcie_ep_set_msi(struct pci_epc *epc, u8 func_no, u8 vfunc_no,
>  	reg = ep_func->msi_cap + func_offset + PCI_MSI_FLAGS;
>  	val = dw_pcie_readw_dbi(pci, reg);
>  	val &= ~PCI_MSI_FLAGS_QMASK;
> -	val |= (interrupts << 1) & PCI_MSI_FLAGS_QMASK;
> +	val |= FIELD_PREP(PCI_MSI_FLAGS_QMASK, interrupts);
>  	dw_pcie_dbi_ro_wr_en(pci);
>  	dw_pcie_writew_dbi(pci, reg, val);
>  	dw_pcie_dbi_ro_wr_dis(pci);
> @@ -584,7 +585,7 @@ int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
>  
>  	reg = ep_func->msix_cap + func_offset + PCI_MSIX_TABLE;
>  	tbl_offset = dw_pcie_readl_dbi(pci, reg);
> -	bir = (tbl_offset & PCI_MSIX_TABLE_BIR);
> +	bir = FIELD_GET(PCI_MSIX_TABLE_BIR, tbl_offset);
>  	tbl_offset &= PCI_MSIX_TABLE_OFFSET;
>  
>  	msix_tbl = ep->epf_bar[bir]->addr + tbl_offset;
> diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
> index 248cd9347e8f..12d5ab2f5219 100644
> --- a/drivers/pci/controller/dwc/pcie-tegra194.c
> +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
> @@ -126,7 +126,6 @@
>  
>  #define APPL_LTR_MSG_1				0xC4
>  #define LTR_MSG_REQ				BIT(15)
> -#define LTR_MST_NO_SNOOP_SHIFT			16
>  
>  #define APPL_LTR_MSG_2				0xC8
>  #define APPL_LTR_MSG_2_LTR_MSG_REQ_STATE	BIT(3)
> @@ -496,8 +495,8 @@ static irqreturn_t tegra_pcie_ep_irq_thread(int irq, void *arg)
>  		ktime_t timeout;
>  
>  		/* 110us for both snoop and no-snoop */
> -		val = 110 | (2 << PCI_LTR_SCALE_SHIFT) | LTR_MSG_REQ;
> -		val |= (val << LTR_MST_NO_SNOOP_SHIFT);
> +		val = 110 | FIELD_PREP(PCI_LTR_SCALE_SHIFT, 2) | LTR_MSG_REQ;
> +		val |= FIELD_PREP(PCI_LTR_NOSNOOP_VALUE, val);
>  		appl_writel(pcie, val, APPL_LTR_MSG_1);
>  
>  		/* Send LTR upstream */
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index e5f558d96493..495f0ae4ecd5 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -975,6 +975,8 @@
>  #define  PCI_LTR_VALUE_MASK	0x000003ff
>  #define  PCI_LTR_SCALE_MASK	0x00001c00
>  #define  PCI_LTR_SCALE_SHIFT	10
> +#define  PCI_LTR_NOSNOOP_VALUE	0x03ff0000 /* Max No-Snoop Latency Value */
> +#define  PCI_LTR_NOSNOOP_SCALE	0x1c000000 /* Scale for Max Value */
>  #define PCI_EXT_CAP_LTR_SIZEOF	8
>  
>  /* Access Control Service */
> -- 
> 2.30.2
>