Re: [PATCH v7 03/14] PCI: cadence: Convert all r/w accessors to perform only 32-bit accesses

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Mon, Jul 13, 2020 at 04:31:30PM +0530, Kishon Vijay Abraham I wrote:
> Certain platforms like TI's J721E using Cadence PCIe IP can perform only
> 32-bit accesses for reading or writing to Cadence registers. Convert all
> read and write accesses to 32-bit in Cadence PCIe driver in preparation
> for adding PCIe support in TI's J721E SoC.
> 
> Also add spin lock to disable interrupts while modifying PCI_STATUS
> register while raising legacy interrupt since PCI_STATUS is accessible
> by both remote RC and EP and time between read and write should be
> minimized.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> ---
>  .../pci/controller/cadence/pcie-cadence-ep.c  |  4 +
>  drivers/pci/controller/cadence/pcie-cadence.h | 76 ++++++++++++++-----
>  2 files changed, 62 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> index 4a829ccff7d0..c6eb2db94680 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
> +++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> @@ -228,6 +228,7 @@ static void cdns_pcie_ep_assert_intx(struct cdns_pcie_ep *ep, u8 fn,
>  				     u8 intx, bool is_asserted)
>  {
>  	struct cdns_pcie *pcie = &ep->pcie;
> +	unsigned long flags;
>  	u32 offset;
>  	u16 status;
>  	u8 msg_code;
> @@ -252,11 +253,13 @@ static void cdns_pcie_ep_assert_intx(struct cdns_pcie_ep *ep, u8 fn,
>  		msg_code = MSG_CODE_DEASSERT_INTA + intx;
>  	}
>  
> +	spin_lock_irqsave(&ep->lock, flags);
>  	status = cdns_pcie_ep_fn_readw(pcie, fn, PCI_STATUS);
>  	if (((status & PCI_STATUS_INTERRUPT) != 0) ^ (ep->irq_pending != 0)) {
>  		status ^= PCI_STATUS_INTERRUPT;
>  		cdns_pcie_ep_fn_writew(pcie, fn, PCI_STATUS, status);
>  	}
> +	spin_unlock_irqrestore(&ep->lock, flags);
>  
>  	offset = CDNS_PCIE_NORMAL_MSG_ROUTING(MSG_ROUTING_LOCAL) |
>  		 CDNS_PCIE_NORMAL_MSG_CODE(msg_code) |
> @@ -464,6 +467,7 @@ int cdns_pcie_ep_setup(struct cdns_pcie_ep *ep)
>  	ep->irq_pci_addr = CDNS_PCIE_EP_IRQ_PCI_ADDR_NONE;
>  	/* Reserve region 0 for IRQs */
>  	set_bit(0, &ep->ob_region_map);
> +	spin_lock_init(&ep->lock);
>  
>  	return 0;
>  
> diff --git a/drivers/pci/controller/cadence/pcie-cadence.h b/drivers/pci/controller/cadence/pcie-cadence.h
> index bc49c22e48a9..a45c11158f49 100644
> --- a/drivers/pci/controller/cadence/pcie-cadence.h
> +++ b/drivers/pci/controller/cadence/pcie-cadence.h
> @@ -304,6 +304,9 @@ struct cdns_pcie_rc {
>   * @irq_pci_fn: the latest PCI function that has updated the mapping of
>   *		the MSI/legacy IRQ dedicated outbound region.
>   * @irq_pending: bitmask of asserted legacy IRQs.
> + * @lock: spin lock to disable interrupts while modifying PCIe controller
> + *        registers fields (RMW) accessible by both remote RC and EP to
> + *        minimize time between read and write
>   */
>  struct cdns_pcie_ep {
>  	struct cdns_pcie	pcie;
> @@ -315,54 +318,94 @@ struct cdns_pcie_ep {
>  	u64			irq_pci_addr;
>  	u8			irq_pci_fn;
>  	u8			irq_pending;
> +	/* protect writing to PCI_STATUS while raising legacy interrupts */
> +	spinlock_t		lock;
>  };
>  
>  
>  /* Register access */
> -static inline void cdns_pcie_writeb(struct cdns_pcie *pcie, u32 reg, u8 value)
> +static inline void cdns_pcie_writel(struct cdns_pcie *pcie, u32 reg, u32 value)
>  {
> -	writeb(value, pcie->reg_base + reg);
> +	writel(value, pcie->reg_base + reg);
>  }
>  
> -static inline void cdns_pcie_writew(struct cdns_pcie *pcie, u32 reg, u16 value)
> +static inline u32 cdns_pcie_readl(struct cdns_pcie *pcie, u32 reg)
>  {
> -	writew(value, pcie->reg_base + reg);
> +	return readl(pcie->reg_base + reg);
>  }
>  
> -static inline void cdns_pcie_writel(struct cdns_pcie *pcie, u32 reg, u32 value)
> +static inline u32 cdns_pcie_read_sz(void __iomem *addr, int size)
>  {
> -	writel(value, pcie->reg_base + reg);
> +	void __iomem *aligned_addr = PTR_ALIGN_DOWN(addr, 0x4);
> +	unsigned int offset = (unsigned long)addr & 0x3;
> +	u32 val = readl(aligned_addr);
> +
> +	if (!IS_ALIGNED((uintptr_t)addr, size)) {
> +		WARN(1, "Address %p and size %d are not aligned\n", addr, size);

This is overkill - please consider a less severe logging (eg pr_warn()).

https://www.kernel.org/doc/html/latest/process/deprecated.html

Same below. I can make these changes before applying but the series
does not apply to v5.8-rc1, please rebase it and I will apply then.

Thanks,
Lorenzo

> +		return 0;
> +	}
> +
> +	if (size > 2)
> +		return val;
> +
> +	return (val >> (8 * offset)) & ((1 << (size * 8)) - 1);
>  }
>  
> -static inline u32 cdns_pcie_readl(struct cdns_pcie *pcie, u32 reg)
> +static inline void cdns_pcie_write_sz(void __iomem *addr, int size, u32 value)
>  {
> -	return readl(pcie->reg_base + reg);
> +	void __iomem *aligned_addr = PTR_ALIGN_DOWN(addr, 0x4);
> +	unsigned int offset = (unsigned long)addr & 0x3;
> +	u32 mask;
> +	u32 val;
> +
> +	if (!IS_ALIGNED((uintptr_t)addr, size)) {
> +		WARN(1, "Address %p and size %d are not aligned\n", addr, size);
> +		return;
> +	}
> +
> +	if (size > 2) {
> +		writel(value, addr);
> +		return;
> +	}
> +
> +	mask = ~(((1 << (size * 8)) - 1) << (offset * 8));
> +	val = readl(aligned_addr) & mask;
> +	val |= value << (offset * 8);
> +	writel(val, aligned_addr);
>  }
>  
>  /* Root Port register access */
>  static inline void cdns_pcie_rp_writeb(struct cdns_pcie *pcie,
>  				       u32 reg, u8 value)
>  {
> -	writeb(value, pcie->reg_base + CDNS_PCIE_RP_BASE + reg);
> +	void __iomem *addr = pcie->reg_base + CDNS_PCIE_RP_BASE + reg;
> +
> +	cdns_pcie_write_sz(addr, 0x1, value);
>  }
>  
>  static inline void cdns_pcie_rp_writew(struct cdns_pcie *pcie,
>  				       u32 reg, u16 value)
>  {
> -	writew(value, pcie->reg_base + CDNS_PCIE_RP_BASE + reg);
> +	void __iomem *addr = pcie->reg_base + CDNS_PCIE_RP_BASE + reg;
> +
> +	cdns_pcie_write_sz(addr, 0x2, value);
>  }
>  
>  /* Endpoint Function register access */
>  static inline void cdns_pcie_ep_fn_writeb(struct cdns_pcie *pcie, u8 fn,
>  					  u32 reg, u8 value)
>  {
> -	writeb(value, pcie->reg_base + CDNS_PCIE_EP_FUNC_BASE(fn) + reg);
> +	void __iomem *addr = pcie->reg_base + CDNS_PCIE_EP_FUNC_BASE(fn) + reg;
> +
> +	cdns_pcie_write_sz(addr, 0x1, value);
>  }
>  
>  static inline void cdns_pcie_ep_fn_writew(struct cdns_pcie *pcie, u8 fn,
>  					  u32 reg, u16 value)
>  {
> -	writew(value, pcie->reg_base + CDNS_PCIE_EP_FUNC_BASE(fn) + reg);
> +	void __iomem *addr = pcie->reg_base + CDNS_PCIE_EP_FUNC_BASE(fn) + reg;
> +
> +	cdns_pcie_write_sz(addr, 0x2, value);
>  }
>  
>  static inline void cdns_pcie_ep_fn_writel(struct cdns_pcie *pcie, u8 fn,
> @@ -371,14 +414,11 @@ static inline void cdns_pcie_ep_fn_writel(struct cdns_pcie *pcie, u8 fn,
>  	writel(value, pcie->reg_base + CDNS_PCIE_EP_FUNC_BASE(fn) + reg);
>  }
>  
> -static inline u8 cdns_pcie_ep_fn_readb(struct cdns_pcie *pcie, u8 fn, u32 reg)
> -{
> -	return readb(pcie->reg_base + CDNS_PCIE_EP_FUNC_BASE(fn) + reg);
> -}
> -
>  static inline u16 cdns_pcie_ep_fn_readw(struct cdns_pcie *pcie, u8 fn, u32 reg)
>  {
> -	return readw(pcie->reg_base + CDNS_PCIE_EP_FUNC_BASE(fn) + reg);
> +	void __iomem *addr = pcie->reg_base + CDNS_PCIE_EP_FUNC_BASE(fn) + reg;
> +
> +	return cdns_pcie_read_sz(addr, 0x2);
>  }
>  
>  static inline u32 cdns_pcie_ep_fn_readl(struct cdns_pcie *pcie, u8 fn, u32 reg)
> -- 
> 2.17.1
>