Re: Onboard SD card doesn't work anymore after the 'mmc-v5.4-2' updates

[Christian Zigotzky <chzigotzky@xxxxxxxxxxx>]

FYI: The onboard SD card works also with the RC6 of kernel 5.4 with the 
patch below.

-- Christian

On 23 October 2019 at 4:20pm, Christian Zigotzky wrote:
> Hello,
>
> The patch below works. I compiled the RC4 of kernel 5.4 with this patch today and the onboard SD card works without any problems.
>
> Thanks!
>
> Christian
>
> > On 23. Oct 2019, at 07:42, Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote:
> >
> > Russell King - ARM Linux admin <linux@xxxxxxxxxxxxxxx> writes:
> > > > On Tue, Oct 15, 2019 at 03:12:49PM +0200, Christian Zigotzky wrote:
> > > > Hello Russell,
> > > >
> > > > You asked me about "dma-coherent" in the Cyrus device tree. Unfortunately I
> > > > don't find the property "dma-coherent" in the dtb source files.
> > > >
> > > > Output of "fdtdump cyrus_p5020_eth_poweroff.dtb | grep dma":
> > > >
> > > > dma0 = "/soc@ffe000000/dma@100300";
> > > >          dma1 = "/soc@ffe000000/dma@101300";
> > > >          dma@100300 {
> > > >              compatible = "fsl,eloplus-dma";
> > > >              dma-channel@0 {
> > > >                  compatible = "fsl,eloplus-dma-channel";
> > > >              dma-channel@80 {
> > > >                  compatible = "fsl,eloplus-dma-channel";
> > > >              dma-channel@100 {
> > > >                  compatible = "fsl,eloplus-dma-channel";
> > > >              dma-channel@180 {
> > > >                  compatible = "fsl,eloplus-dma-channel";
> > > >          dma@101300 {
> > > >              compatible = "fsl,eloplus-dma";
> > > >              dma-channel@0 {
> > > >                  compatible = "fsl,eloplus-dma-channel";
> > > >              dma-channel@80 {
> > > >                  compatible = "fsl,eloplus-dma-channel";
> > > >              dma-channel@100 {
> > > >                  compatible = "fsl,eloplus-dma-channel";
> > > >              dma-channel@180 {
> > > >                  compatible = "fsl,eloplus-dma-channel";
> > > Hmm, so it looks like PowerPC doesn't mark devices that are dma
> > > coherent with a property that describes them as such.
> > >
> > > I think this opens a wider question - what should of_dma_is_coherent()
> > > return for PowerPC?  It seems right now that it returns false for
> > > devices that are DMA coherent, which seems to me to be a recipe for
> > > future mistakes.
> > Right, it seems of_dma_is_coherent() has baked in the assumption that
> > devices are non-coherent unless explicitly marked as coherent.
> >
> > Which is wrong on all or at least most existing powerpc systems
> > according to Ben.
> >
> > > Any ideas from the PPC maintainers?
> > Fixing it at the source seems like the best option to prevent future
> > breakage.
> >
> > So I guess that would mean making of_dma_is_coherent() return true/false
> > based on CONFIG_NOT_COHERENT_CACHE on powerpc.
> >
> > We could do it like below, which would still allow the dma-coherent
> > property to work if it ever makes sense on a future powerpc platform.
> >
> > I don't really know any of this embedded stuff well, so happy to take
> > other suggestions on how to handle this mess.
> >
> > cheers
> >
> >
> > diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
> > index 25aaa3903000..b96c9010acb6 100644
> > --- a/arch/powerpc/kernel/setup-common.c
> > +++ b/arch/powerpc/kernel/setup-common.c
> > @@ -760,6 +760,22 @@ static int __init check_cache_coherency(void)
> > late_initcall(check_cache_coherency);
> > #endif /* CONFIG_CHECK_CACHE_COHERENCY */
> >
> > +#ifndef CONFIG_NOT_COHERENT_CACHE
> > +/*
> > + * For historical reasons powerpc kernels are built with hard wired knowledge of
> > + * whether or not DMA accesses are cache coherent. Additionally device trees on
> > + * powerpc do not typically support the dma-coherent property.
> > + *
> > + * So when we know that DMA is coherent, override arch_of_dma_is_coherent() to
> > + * tell the drivers/of code that all devices are coherent regardless of whether
> > + * they have a dma-coherent property.
> > + */
> > +bool arch_of_dma_is_coherent(struct device_node *np)
> > +{
> > +    return true;
> > +}
> > +#endif
> > +
> > #ifdef CONFIG_DEBUG_FS
> > struct dentry *powerpc_debugfs_root;
> > EXPORT_SYMBOL(powerpc_debugfs_root);
> > diff --git a/drivers/of/address.c b/drivers/of/address.c
> > index 978427a9d5e6..3a4b2949a322 100644
> > --- a/drivers/of/address.c
> > +++ b/drivers/of/address.c
> > @@ -993,6 +993,14 @@ int of_dma_get_range(struct device_node *np, u64 *dma_addr, u64 *paddr, u64 *siz
> > }
> > EXPORT_SYMBOL_GPL(of_dma_get_range);
> >
> > +/*
> > + * arch_of_dma_is_coherent - Arch hook to determine if device is coherent for DMA
> > + */
> > +bool __weak arch_of_dma_is_coherent(struct device_node *np)
> > +{
> > +    return false;
> > +}
> > +
> > /**
> >   * of_dma_is_coherent - Check if device is coherent
> >   * @np:    device node
> > @@ -1002,8 +1010,12 @@ EXPORT_SYMBOL_GPL(of_dma_get_range);
> >   */
> > bool of_dma_is_coherent(struct device_node *np)
> > {
> > -    struct device_node *node = of_node_get(np);
> > +    struct device_node *node;
> > +
> > +    if (arch_of_dma_is_coherent(np))
> > +        return true;
> >
> > +    np = of_node_get(np);
> >     while (node) {
> >         if (of_property_read_bool(node, "dma-coherent")) {
> >             of_node_put(node);