RE: [PATCH v4 4/6] ata: ahci_imx: Add 32bits DMA limit for i.MX8QM AHCI SATA

[Hongxing Zhu <hongxing.zhu@nxp.com>]

> -----Original Message-----
> From: Niklas Cassel <cassel@kernel.org>
> Sent: 2024年8月8日 6:35
> To: Hongxing Zhu <hongxing.zhu@nxp.com>
> Cc: tj@kernel.org; dlemoal@kernel.org; robh@kernel.org; krzk+dt@kernel.org;
> conor+dt@kernel.org; shawnguo@kernel.org; s.hauer@pengutronix.de;
> festevam@gmail.com; linux-ide@vger.kernel.org; stable@vger.kernel.org;
> devicetree@vger.kernel.org; linux-kernel@vger.kernel.org;
> linux-arm-kernel@lists.infradead.org; imx@lists.linux.dev;
> kernel@pengutronix.de
> Subject: Re: [PATCH v4 4/6] ata: ahci_imx: Add 32bits DMA limit for i.MX8QM
> AHCI SATA
> 
> On Fri, Aug 02, 2024 at 02:30:45AM +0000, Hongxing Zhu wrote:
> > >
> > > Does this solve your problem:
> > > diff --git a/drivers/ata/libahci_platform.c
> > > b/drivers/ata/libahci_platform.c index 581704e61f28..fc86e2c8c42b
> > > 100644
> > > --- a/drivers/ata/libahci_platform.c
> > > +++ b/drivers/ata/libahci_platform.c
> > > @@ -747,12 +747,11 @@ int ahci_platform_init_host(struct
> > > platform_device *pdev,
> > >                         ap->ops = &ata_dummy_port_ops;
> > >         }
> > >
> > > -       if (hpriv->cap & HOST_CAP_64) {
> > > -               rc = dma_coerce_mask_and_coherent(dev,
> > > DMA_BIT_MASK(64));
> > > -               if (rc) {
> > > -                       dev_err(dev, "Failed to enable 64-bit DMA.\n");
> > > -                       return rc;
> > > -               }
> > > +       rc = dma_coerce_mask_and_coherent(dev,
> > > +                       DMA_BIT_MASK((hpriv->cap & HOST_CAP_64) ?
> 64 :
> > > 32));
> > > +       if (rc) {
> > > +               dev_err(dev, "DMA enable failed\n");
> > > +               return rc;
> > >         }
> > >
> > >         rc = ahci_reset_controller(host);
> > >
> > Hi Niklas:
> > I'm so sorry to reply late.
> > About the 32bit DMA limitation of i.MX8QM AHCI SATA.
> > It's seems that one "dma-ranges" property in the DT can let i.MX8QM
> > SATA  works fine in my past days tests without this commit.
> > How about drop these driver changes, and add "dma-ranges" for i.MX8QM
> SATA?
> > Thanks a lot for your kindly help.
> 
> Hello Richard,
> 
> did you try my suggested patch above?
> 
> 
> If you look at dma-ranges:
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdevicetre
> e-specification.readthedocs.io%2Fen%2Flatest%2Fchapter2-devicetree-basics.ht
> ml%23dma-ranges&data=05%7C02%7Chongxing.zhu%40nxp.com%7C97f87f99
> 37844f97dbf508dcb731345e%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0
> %7C0%7C638586669175980044%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC
> 4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7
> C%7C&sdata=PO0bQVUA7o47HAecOp27TKwwNiG1ydfQq4DTtgEva%2Fg%3D&
> reserved=0
> 
> "dma-ranges" property should be used on a bus device node (such as PCI host
> bridges).
> 
> It does not seem correct to add this property (describing the DMA limit of the
> AHCI controller, a PCI endpoint) on the PCI host bridge/controller.
> 
> This property belongs to the AHCI controller, not the upstream PCI host
> bridge/controller.
> 
> AHCI has a specific register to describe if the hardware can support 64-bit DMA
> addresses or not, so if my suggested patch works for you, it seems like a more
> elegant solution (which also avoids having to abuse device tree properties).
> 
Hi Niklas:
Thank you very much for your kindly reply.
In i.MX8QM, both AHCI and PCIe are contained in HSIO(High Speed IO) module.
The "dma-ranges" property is defined in HSIO dts node actually.

BTW, I had tried the method you mentioned before. Unfortunately, it doesn't
work for i.MX8QM AHCI.

Best Regards
Richard Zhu
> 
> Kind regards,
> Niklas