linux-kernel - Re: [PATCH v2 8/9] PCI: rockchip: Use u32 variable to access 32-bit registers

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Message-ID: <0fa5cef4-7096-7f59-422a-98011d01437c@opensource.wdc.com>
Date:   Wed, 15 Feb 2023 10:34:28 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Rick Wertenbroek <rick.wertenbroek@...il.com>,
        alberto.dassatti@...g-vd.ch
Cc:     xxm@...k-chips.com, rick.wertenbroek@...g-vd.ch,
        stable@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jani Nikula <jani.nikula@...el.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Mikko Kovanen <mikko.kovanen@...amobile.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org
Subject: Re: [PATCH v2 8/9] PCI: rockchip: Use u32 variable to access 32-bit
 registers

On 2/14/23 23:08, Rick Wertenbroek wrote:
> Previously u16 variables were used to access 32-bit registers, this
> resulted in not all of the data being read from the registers. Also
> the left shift of more than 16-bits would result in moving data out
> of the variable. Use u32 variables to access 32-bit registers
> 
> Fixes: cf590b078391 ("PCI: rockchip: Add EP driver for Rockchip PCIe controller")
> Cc: stable@...r.kernel.org
> Signed-off-by: Rick Wertenbroek <rick.wertenbroek@...il.com>
> ---
>  drivers/pci/controller/pcie-rockchip-ep.c | 10 +++++-----
>  drivers/pci/controller/pcie-rockchip.h    |  1 +
>  2 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
> index ca5b363ba..b7865a94e 100644
> --- a/drivers/pci/controller/pcie-rockchip-ep.c
> +++ b/drivers/pci/controller/pcie-rockchip-ep.c
> @@ -292,15 +292,15 @@ static int rockchip_pcie_ep_set_msi(struct pci_epc *epc, u8 fn, u8 vfn,
>  {
>  	struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
>  	struct rockchip_pcie *rockchip = &ep->rockchip;
> -	u16 flags;
> +	u32 flags;
>  
>  	flags = rockchip_pcie_read(rockchip,
>  				   ROCKCHIP_PCIE_EP_FUNC_BASE(fn) +
>  				   ROCKCHIP_PCIE_EP_MSI_CTRL_REG);
>  	flags &= ~ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_MASK;
>  	flags |=
> -	   ((multi_msg_cap << 1) <<  ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_OFFSET) |
> -	   PCI_MSI_FLAGS_64BIT;
> +	   (multi_msg_cap << ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_OFFSET) |

ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_OFFSET is 17 and multi_msg_cap is a u8...
Not nice.

Locally, I added the local variable:

u32 mmc = multi_msg_cap;

And use mmc instead of multi_msg_cap to avoid issues. Also,

> +	   (PCI_MSI_FLAGS_64BIT << ROCKCHIP_PCIE_EP_MSI_FLAGS_OFFSET);
>  	flags &= ~ROCKCHIP_PCIE_EP_MSI_CTRL_MASK_MSI_CAP;
>  	rockchip_pcie_write(rockchip, flags,
>  			    ROCKCHIP_PCIE_EP_FUNC_BASE(fn) +
> @@ -312,7 +312,7 @@ static int rockchip_pcie_ep_get_msi(struct pci_epc *epc, u8 fn, u8 vfn)
>  {
>  	struct rockchip_pcie_ep *ep = epc_get_drvdata(epc);
>  	struct rockchip_pcie *rockchip = &ep->rockchip;
> -	u16 flags;
> +	u32 flags;
>  
>  	flags = rockchip_pcie_read(rockchip,
>  				   ROCKCHIP_PCIE_EP_FUNC_BASE(fn) +
> @@ -374,7 +374,7 @@ static int rockchip_pcie_ep_send_msi_irq(struct rockchip_pcie_ep *ep, u8 fn,
>  					 u8 interrupt_num)
>  {
>  	struct rockchip_pcie *rockchip = &ep->rockchip;
> -	u16 flags, mme, data, data_mask;
> +	u32 flags, mme, data, data_mask;
>  	u8 msi_count;
>  	u64 pci_addr, pci_addr_mask = 0xff;
>  	u32 r;
> diff --git a/drivers/pci/controller/pcie-rockchip.h b/drivers/pci/controller/pcie-rockchip.h
> index e90c2a2b8..11dbf53cd 100644
> --- a/drivers/pci/controller/pcie-rockchip.h
> +++ b/drivers/pci/controller/pcie-rockchip.h
> @@ -227,6 +227,7 @@
>  #define ROCKCHIP_PCIE_EP_CMD_STATUS			0x4
>  #define   ROCKCHIP_PCIE_EP_CMD_STATUS_IS		BIT(19)
>  #define ROCKCHIP_PCIE_EP_MSI_CTRL_REG			0x90
> +#define   ROCKCHIP_PCIE_EP_MSI_FLAGS_OFFSET			16

You are not using this macro anywhere. The name is also not very
descriptive. Better have it as:

#define   ROCKCHIP_PCIE_EP_MSI_CTRL_ME		BIT(16)

to match the TRM name and be clear that the bit indicates if MSI is
enabled or not.

>  #define   ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_OFFSET		17
>  #define   ROCKCHIP_PCIE_EP_MSI_CTRL_MMC_MASK		GENMASK(19, 17)
>  #define   ROCKCHIP_PCIE_EP_MSI_CTRL_MME_OFFSET		20

-- 
Damien Le Moal
Western Digital Research