[PATCH] PCI: rcar-gen4: Isolate 256B MRRS limit only to R-Car Gen4 SoC PCIe controller

[PATCH] PCI: rcar-gen4: Isolate 256B MRRS limit only to R-Car Gen4 SoC PCIe controller

[Marek Vasut]

The R-Car Gen5 SoC PCIe4 controller is not affected by the 256B MRRS
limitation that was present on R-Car Gen4 SoC PCIe controller. Apply
the 256B MRRS limitation workaround to R-Car Gen4 SoC PCIe controller
only. For details of the 256B MRRS limitation, please refer to commit
f0a5c6bd797c ("PCI: rcar-gen4: Limit Max_Read_Request_Size to 256 Bytes") .

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
---
Cc: "Krzysztof Wilczyński" <kwilczynski@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: Magnus Damm <magnus.damm@gmail.com>
Cc: Manivannan Sadhasivam <mani@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
---
 drivers/pci/controller/dwc/pcie-rcar-gen4.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-rcar-gen4.c b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
index 9a64a9f4ab0d1..1e4405181eef3 100644
--- a/drivers/pci/controller/dwc/pcie-rcar-gen4.c
+++ b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
@@ -99,6 +99,7 @@ struct rcar_gen4_pcie_drvdata {
 	int (*ltssm_control)(struct rcar_gen4_pcie *rcar, bool enable);
 	int (*speed_control)(struct rcar_gen4_pcie *rcar);
 	enum dw_pcie_device_mode mode;
+	bool mrrs_256b_limit;
 };
 
 struct rcar_gen4_pcie {
@@ -663,7 +664,7 @@ static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp)
 	if (ret)
 		return ret;
 
-	if (pp->bridge)
+	if (rcar->drvdata->mrrs_256b_limit && pp->bridge)
 		pp->bridge->enable_device = rcar_gen4_pcie_enable_device;
 
 	reset_control_assert(rcar->perst);
@@ -1136,6 +1137,7 @@ static struct rcar_gen4_pcie_drvdata drvdata_r8a779f0_pcie = {
 	.ltssm_control = r8a779f0_pcie_ltssm_control,
 	.speed_control = rcar_gen4_pcie_speed_control,
 	.mode = DW_PCIE_RC_TYPE,
+	.mrrs_256b_limit = true,
 };
 
 static struct rcar_gen4_pcie_drvdata drvdata_r8a779f0_pcie_ep = {
@@ -1144,6 +1146,7 @@ static struct rcar_gen4_pcie_drvdata drvdata_r8a779f0_pcie_ep = {
 	.ltssm_control = r8a779f0_pcie_ltssm_control,
 	.speed_control = rcar_gen4_pcie_speed_control,
 	.mode = DW_PCIE_EP_TYPE,
+	.mrrs_256b_limit = true,
 };
 
 static struct rcar_gen4_pcie_drvdata drvdata_rcar_gen4_pcie = {
@@ -1152,6 +1155,7 @@ static struct rcar_gen4_pcie_drvdata drvdata_rcar_gen4_pcie = {
 	.ltssm_control = rcar_gen4_pcie_ltssm_control,
 	.speed_control = rcar_gen4_pcie_speed_control,
 	.mode = DW_PCIE_RC_TYPE,
+	.mrrs_256b_limit = true,
 };
 
 static struct rcar_gen4_pcie_drvdata drvdata_rcar_gen4_pcie_ep = {
@@ -1160,6 +1164,7 @@ static struct rcar_gen4_pcie_drvdata drvdata_rcar_gen4_pcie_ep = {
 	.ltssm_control = rcar_gen4_pcie_ltssm_control,
 	.speed_control = rcar_gen4_pcie_speed_control,
 	.mode = DW_PCIE_EP_TYPE,
+	.mrrs_256b_limit = true,
 };
 
 static struct rcar_gen4_pcie_drvdata drvdata_rcar_gen5_pcie = {
-- 
2.53.0

Re: [PATCH] PCI: rcar-gen4: Isolate 256B MRRS limit only to R-Car Gen4 SoC PCIe controller

[Manivannan Sadhasivam]

On 2026-10-28 18:21 +0100, Marek Vasut wrote:
> The R-Car Gen5 SoC PCIe4 controller is not affected by the 256B MRRS
> limitation that was present on R-Car Gen4 SoC PCIe controller. Apply
> the 256B MRRS limitation workaround to R-Car Gen4 SoC PCIe controller
> only. For details of the 256B MRRS limitation, please refer to commit
> f0a5c6bd797c ("PCI: rcar-gen4: Limit Max_Read_Request_Size to 256 Bytes") .
> 
> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
> ---
> Cc: "Krzysztof Wilczyński" <kwilczynski@kernel.org>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Geert Uytterhoeven <geert+renesas@glider.be>
> Cc: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Cc: Magnus Damm <magnus.damm@gmail.com>
> Cc: Manivannan Sadhasivam <mani@kernel.org>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-pci@vger.kernel.org
> Cc: linux-renesas-soc@vger.kernel.org
> ---
>  drivers/pci/controller/dwc/pcie-rcar-gen4.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-rcar-gen4.c b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
> index 9a64a9f4ab0d1..1e4405181eef3 100644
> --- a/drivers/pci/controller/dwc/pcie-rcar-gen4.c
> +++ b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
> @@ -99,6 +99,7 @@ struct rcar_gen4_pcie_drvdata {
>  	int (*ltssm_control)(struct rcar_gen4_pcie *rcar, bool enable);
>  	int (*speed_control)(struct rcar_gen4_pcie *rcar);
>  	enum dw_pcie_device_mode mode;
> +	bool mrrs_256b_limit;
>  };
>  
>  struct rcar_gen4_pcie {
> @@ -663,7 +664,7 @@ static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp)
>  	if (ret)
>  		return ret;
>  
> -	if (pp->bridge)
> +	if (rcar->drvdata->mrrs_256b_limit && pp->bridge)
>  		pp->bridge->enable_device = rcar_gen4_pcie_enable_device;

I'd suggest moving this check inside enable_device() callback to make it clear
where exactly the skipping happens.

- Mani

Re: [PATCH] PCI: rcar-gen4: Isolate 256B MRRS limit only to R-Car Gen4 SoC PCIe controller

[Marek Vasut]

On 10/30/26 7:06 AM, Manivannan Sadhasivam wrote:

Hello Manivannan,

>> diff --git a/drivers/pci/controller/dwc/pcie-rcar-gen4.c b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
>> index 9a64a9f4ab0d1..1e4405181eef3 100644
>> --- a/drivers/pci/controller/dwc/pcie-rcar-gen4.c
>> +++ b/drivers/pci/controller/dwc/pcie-rcar-gen4.c
>> @@ -99,6 +99,7 @@ struct rcar_gen4_pcie_drvdata {
>>   	int (*ltssm_control)(struct rcar_gen4_pcie *rcar, bool enable);
>>   	int (*speed_control)(struct rcar_gen4_pcie *rcar);
>>   	enum dw_pcie_device_mode mode;
>> +	bool mrrs_256b_limit;
>>   };
>>   
>>   struct rcar_gen4_pcie {
>> @@ -663,7 +664,7 @@ static int rcar_gen4_pcie_host_init(struct dw_pcie_rp *pp)
>>   	if (ret)
>>   		return ret;
>>   
>> -	if (pp->bridge)
>> +	if (rcar->drvdata->mrrs_256b_limit && pp->bridge)
>>   		pp->bridge->enable_device = rcar_gen4_pcie_enable_device;
> 
> I'd suggest moving this check inside enable_device() callback to make it clear
> where exactly the skipping happens.

If we do that, we would end up with assigning a callback which always 
does nothing on R-Car Gen5 (SoC with rcar->drvdata->mrrs_256b_limit = 
false), that is not good. I think it is better to simply not assign the 
callback on R-Car Gen5 at all. Hence this here.

-- 
Best regards,
Marek Vasut