Re: [PATCH v5 3/3] mmc: Add driver for LiteX's LiteSDCard interface

On Sun, Dec 26, 2021 at 03:13:21PM +0200, Andy Shevchenko wrote:

On Sun, Dec 26, 2021 at 1:45 PM Gabriel L. Somlo [off-list ref] wrote:

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On Sat, Dec 25, 2021 at 06:43:22PM +0200, Andy Shevchenko wrote:

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On Wed, Dec 15, 2021 at 10:00 PM Gabriel Somlo [off-list ref] wrote:

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This is wrong. It missed the deferred probe, for example.

The best approach is

ret = platform_get_irq_optional(...);
if (ret < 0 && ret != -ENXIO)
  return ret;
if (ret > 0)
  ...we got it...

It will allow the future API fix of platform_get_irq_optional() to be
really optional.

Thanks for the example. I still need to work in a decision to use
polling, though. How about something like this instead:

ret = platform_get_irq_optional(...);
if (ret == -ENXIO)
  goto use_polling;
if (ret < 0)
  return ret; // deferred probe (-EAGAIN likely?)
if (ret > 0)
  ...we got it, keep going...

This doesn't define what you should do when you get 0.
I suggest to take my variant with below modification

if (ret > 0)
  ...we have IRQ...
else
  goto USE POLLING;

It will take care of the case.

 
OK, will do.

...

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+#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT

Why under ifdeffery?

Because I only want to do it on 64-bit capable architectures.

The alternative would be to call

  dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));

on *all* architectures, but ignore the returned error (-EIO,
presumably on architetures that only support 32-bit DMA).

I don't understand why you are supposed to ignore errors and why you
expect to get such.

If I call `dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));`
on a machine where `CONFIG_ARCH_DMA_ADDR_T_64BIT` is *not* set, I
expect an error. The implicit default
(per Documentation/core-api/dma-api-howto.rst), is DMA_BIT_MASK(32).
I'm working under the impression that on machines with
CONFIG_ARCH_DMA_ADDR_T_64BIT I should increase that to DMA_BIT_MASK(64).

So if I don't #ifdef it, that call will fail on machines supporting
only 32-bits.

What am I missing?

Thanks,
--Gabriel
 

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Do you think that would be cleaner?

-- 
With Best Regards,
Andy Shevchenko