linux-kernel - Re: [PATCH 04/13] PCI: dwc: Refactor imx6 to use dw_pcie_clear_and_set

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Message-ID: <1726d3ae-ce10-492a-b19b-4ee6ae6f2c2f@163.com>
Date: Thu, 12 Jun 2025 08:46:54 +0800
From: Hans Zhang <18255117159@....com>
To: Frank Li <Frank.li@....com>
Cc: lpieralisi@...nel.org, bhelgaas@...gle.com, mani@...nel.org,
 kwilczynski@...nel.org, robh@...nel.org, jingoohan1@...il.com,
 linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/13] PCI: dwc: Refactor imx6 to use
 dw_pcie_clear_and_set_dword()



On 2025/6/12 02:38, Frank Li wrote:
> On Thu, Jun 12, 2025 at 12:31:21AM +0800, Hans Zhang wrote:
> 
> Subject should be
> 
> PCI: dwc: imx6: Refactor code by using dw_pcie_clear_and_set_dword()
> 
> tag "imx6:" should after "dwc:"
> 

Dear Frank,

Thank you very much for your reply and suggestions. Will change.

Best regards,
Hans

> Reviewed-by: Frank Li <Frank.Li@....com>
> 
>> i.MX6 PCIe driver contains multiple read-modify-write sequences for
>> link training and speed configuration. These operations manually handle
>> bit masking and shifting to update specific fields in control registers,
>> particularly for link capabilities and speed change initiation.
>>
>> Refactor link capability configuration and speed change handling using
>> dw_pcie_clear_and_set_dword(). The helper simplifies LNKCAP modification
>> by encapsulating bit clear/set operations and eliminates intermediate
>> variables. For speed change control, replace explicit bit manipulation
>> with direct register updates through the helper.
>>
>> Adopting the standard interface reduces code complexity in link training
>> paths and ensures consistent handling of speed-related bits. The change
>> also prepares the driver for future enhancements to Gen3 link training
>> by centralizing bit manipulation logic.
>>
>> Signed-off-by: Hans Zhang <18255117159@....com>
>> ---
>>   drivers/pci/controller/dwc/pci-imx6.c | 26 ++++++++++----------------
>>   1 file changed, 10 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
>> index 5a38cfaf989b..3004e432f013 100644
>> --- a/drivers/pci/controller/dwc/pci-imx6.c
>> +++ b/drivers/pci/controller/dwc/pci-imx6.c
>> @@ -941,7 +941,6 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
>>   	struct imx_pcie *imx_pcie = to_imx_pcie(pci);
>>   	struct device *dev = pci->dev;
>>   	u8 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
>> -	u32 tmp;
>>   	int ret;
>>
>>   	if (!(imx_pcie->drvdata->flags &
>> @@ -956,10 +955,9 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
>>   	 * bus will not be detected at all.  This happens with PCIe switches.
>>   	 */
>>   	dw_pcie_dbi_ro_wr_en(pci);
>> -	tmp = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
>> -	tmp &= ~PCI_EXP_LNKCAP_SLS;
>> -	tmp |= PCI_EXP_LNKCAP_SLS_2_5GB;
>> -	dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, tmp);
>> +	dw_pcie_clear_and_set_dword(pci, offset + PCI_EXP_LNKCAP,
>> +				    PCI_EXP_LNKCAP_SLS,
>> +				    PCI_EXP_LNKCAP_SLS_2_5GB);
>>   	dw_pcie_dbi_ro_wr_dis(pci);
>>
>>   	/* Start LTSSM. */
>> @@ -972,18 +970,16 @@ static int imx_pcie_start_link(struct dw_pcie *pci)
>>
>>   		/* Allow faster modes after the link is up */
>>   		dw_pcie_dbi_ro_wr_en(pci);
>> -		tmp = dw_pcie_readl_dbi(pci, offset + PCI_EXP_LNKCAP);
>> -		tmp &= ~PCI_EXP_LNKCAP_SLS;
>> -		tmp |= pci->max_link_speed;
>> -		dw_pcie_writel_dbi(pci, offset + PCI_EXP_LNKCAP, tmp);
>> +		dw_pcie_clear_and_set_dword(pci, offset + PCI_EXP_LNKCAP,
>> +					    PCI_EXP_LNKCAP_SLS,
>> +					    pci->max_link_speed);
>>
>>   		/*
>>   		 * Start Directed Speed Change so the best possible
>>   		 * speed both link partners support can be negotiated.
>>   		 */
>> -		tmp = dw_pcie_readl_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL);
>> -		tmp |= PORT_LOGIC_SPEED_CHANGE;
>> -		dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, tmp);
>> +		dw_pcie_clear_and_set_dword(pci, PCIE_LINK_WIDTH_SPEED_CONTROL,
>> +					    0, PORT_LOGIC_SPEED_CHANGE);
>>   		dw_pcie_dbi_ro_wr_dis(pci);
>>
>>   		ret = imx_pcie_wait_for_speed_change(imx_pcie);
>> @@ -1295,7 +1291,6 @@ static void imx_pcie_host_post_init(struct dw_pcie_rp *pp)
>>   {
>>   	struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>>   	struct imx_pcie *imx_pcie = to_imx_pcie(pci);
>> -	u32 val;
>>
>>   	if (imx_pcie->drvdata->flags & IMX_PCIE_FLAG_8GT_ECN_ERR051586) {
>>   		/*
>> @@ -1310,9 +1305,8 @@ static void imx_pcie_host_post_init(struct dw_pcie_rp *pp)
>>   		 * to 0.
>>   		 */
>>   		dw_pcie_dbi_ro_wr_en(pci);
>> -		val = dw_pcie_readl_dbi(pci, GEN3_RELATED_OFF);
>> -		val &= ~GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL;
>> -		dw_pcie_writel_dbi(pci, GEN3_RELATED_OFF, val);
>> +		dw_pcie_clear_and_set_dword(pci, GEN3_RELATED_OFF,
>> +					    GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL, 0);
>>   		dw_pcie_dbi_ro_wr_dis(pci);
>>   	}
>>   }
>> --
>> 2.25.1
>>