Re: [PATCH 06/10] PCI/DPC: Use FIELD_GET()

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

On Tue, 10 Oct 2023, Bjorn Helgaas wrote:

> From: Bjorn Helgaas <bhelgaas@google.com>
> 
> Use FIELD_GET() to remove dependences on the field position, i.e., the
> shift value.  No functional change intended.
> 
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> ---
>  drivers/pci/pcie/dpc.c        | 9 +++++----
>  drivers/pci/quirks.c          | 2 +-
>  include/uapi/linux/pci_regs.h | 1 +
>  3 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> index 3ceed8e3de41..6e551f34ec63 100644
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -8,6 +8,7 @@
>  
>  #define dev_fmt(fmt) "DPC: " fmt
>  
> +#include <linux/bitfield.h>
>  #include <linux/aer.h>
>  #include <linux/delay.h>
>  #include <linux/interrupt.h>
> @@ -202,7 +203,7 @@ static void dpc_process_rp_pio_error(struct pci_dev *pdev)
>  
>  	/* Get First Error Pointer */
>  	pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &dpc_status);
> -	first_error = (dpc_status & 0x1f00) >> 8;
> +	first_error = FIELD_GET(PCI_EXP_DPC_STATUS_FIRST_ERR, dpc_status);
>  
>  	for (i = 0; i < ARRAY_SIZE(rp_pio_error_string); i++) {
>  		if ((status & ~mask) & (1 << i))
> @@ -270,8 +271,8 @@ void dpc_process_error(struct pci_dev *pdev)
>  	pci_info(pdev, "containment event, status:%#06x source:%#06x\n",
>  		 status, source);
>  
> -	reason = (status & PCI_EXP_DPC_STATUS_TRIGGER_RSN) >> 1;
> -	ext_reason = (status & PCI_EXP_DPC_STATUS_TRIGGER_RSN_EXT) >> 5;
> +	reason = FIELD_GET(PCI_EXP_DPC_STATUS_TRIGGER_RSN, status);
> +	ext_reason = FIELD_GET(PCI_EXP_DPC_STATUS_TRIGGER_RSN_EXT, status);
>  	pci_warn(pdev, "%s detected\n",
>  		 (reason == 0) ? "unmasked uncorrectable error" :
>  		 (reason == 1) ? "ERR_NONFATAL" :

BTW, it seems we're doing overlapping work here with many of these 
patches. It takes some time to think these through one by one, I don't 
just autorun through them with coccinelle so I've not posted my changes
yet.

I went to a different direction here and named all the reasons too with 
defines and used & to get the reason in order to be able to compare with 
the named reasons.

You also missed convering one 0xfff4 to use define (although I suspect it 
never was your goal to go beyond FIELD_GET() here).
 
> @@ -338,7 +339,7 @@ void pci_dpc_init(struct pci_dev *pdev)
>  	/* Quirks may set dpc_rp_log_size if device or firmware is buggy */
>  	if (!pdev->dpc_rp_log_size) {
>  		pdev->dpc_rp_log_size =
> -			(cap & PCI_EXP_DPC_RP_PIO_LOG_SIZE) >> 8;
> +				FIELD_GET(PCI_EXP_DPC_RP_PIO_LOG_SIZE, cap);
>  		if (pdev->dpc_rp_log_size < 4 || pdev->dpc_rp_log_size > 9) {
>  			pci_err(pdev, "RP PIO log size %u is invalid\n",
>  				pdev->dpc_rp_log_size);
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index eeec1d6f9023..a9fdc2e3f110 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -6154,7 +6154,7 @@ static void dpc_log_size(struct pci_dev *dev)
>  	if (!(val & PCI_EXP_DPC_CAP_RP_EXT))
>  		return;
>  
> -	if (!((val & PCI_EXP_DPC_RP_PIO_LOG_SIZE) >> 8)) {
> +	if (FIELD_GET(PCI_EXP_DPC_RP_PIO_LOG_SIZE, val) == 0) {
>  		pci_info(dev, "Overriding RP PIO Log Size to 4\n");
>  		dev->dpc_rp_log_size = 4;
>  	}
> diff --git a/include/uapi/linux/pci_regs.h b/include/uapi/linux/pci_regs.h
> index 833e5fb40ea5..e97a06b50f95 100644
> --- a/include/uapi/linux/pci_regs.h
> +++ b/include/uapi/linux/pci_regs.h
> @@ -1046,6 +1046,7 @@
>  #define  PCI_EXP_DPC_STATUS_INTERRUPT	    0x0008 /* Interrupt Status */
>  #define  PCI_EXP_DPC_RP_BUSY		    0x0010 /* Root Port Busy */
>  #define  PCI_EXP_DPC_STATUS_TRIGGER_RSN_EXT 0x0060 /* Trig Reason Extension */
> +#define  PCI_EXP_DPC_STATUS_FIRST_ERR	    0x1f00 /* RP PIO First Error Ptr */

If you prefer consistency, there already FEP used for "First 
Error Pointer" used in another define.

>  #define PCI_EXP_DPC_SOURCE_ID		 0x0A	/* DPC Source Identifier */



-- 
 i.