Re: [PATCH] fbtft: limit transfer length by spi device limit

[Greg Kroah-Hartman]

On Thu, May 26, 2016 at 07:25:22PM -, Michal Suchanek wrote:
> Some SPI controllers can transfer only small piece of data at a time.
> Since SPI core gained a function to get the maximum transfer length use
> it.
> 
> Signed-off-by: Michal Suchanek 
> Acked-by: Noralf Trønnes 
> ---
> 
>  Tested on sunxi spi with DMA enabled and disabled. Makes a visible speed
> difference and display works in either case.
> 
>  drivers/staging/fbtft/fbtft-core.c | 9 +
>  1 file changed, 9 insertions(+)

This patch adds a build warning to the tree, so I can't take it.

Please fix up and resend.

thanks,

greg k-h
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Re: [PATCH] fbtft: limit transfer length by spi device limit

[Noralf Trønnes]

Den 26.05.2016 21:25, skrev Michal Suchanek:

Some SPI controllers can transfer only small piece of data at a time.
Since SPI core gained a function to get the maximum transfer length use
it.

Signed-off-by: Michal Suchanek 
---

  Tested on sunxi spi with DMA enabled and disabled. Makes a visible speed
difference and display works in either case.

  drivers/staging/fbtft/fbtft-core.c | 9 +
  1 file changed, 9 insertions(+)

diff --git a/drivers/staging/fbtft/fbtft-core.c 
b/drivers/staging/fbtft/fbtft-core.c
index 0c1a77c..f3bdc8f 100644
--- a/drivers/staging/fbtft/fbtft-core.c
+++ b/drivers/staging/fbtft/fbtft-core.c
@@ -1346,6 +1346,15 @@ int fbtft_probe_common(struct fbtft_display *display,
return PTR_ERR(pdata);
}
  
+	if (sdev && (spi_max_transfer_size(sdev) < SIZE_MAX))

+   if ((pdata->txbuflen <= 0) || (pdata->txbuflen > 
spi_max_transfer_size(sdev))) {
+   dev_warn(dev,
+"Limiting used buffer size %i -> %i due to device 
%s transfer size limitation",
+pdata->txbuflen, spi_max_transfer_size(sdev),
+dev_name(>dev));
+   pdata->txbuflen = spi_max_transfer_size(sdev);
+   }
+
info = fbtft_framebuffer_alloc(display, dev, pdata);
if (!info)
return -ENOMEM;


(Ugh, this code of mine looks worse each time I'm confronted with it.)

You have even taken care of the special txbuflen == -1 value I see,
so I guess this is as good as it gets without any major refactoring, so:

Acked-by: Noralf Trønnes 

And there's no point in doing any refactoring since I'm working on a DRM
successor for fbtft. I have been working on it since the fbdev maintainer
issued the "No more new fbdev drivers, please" call in September and now
it has reached a tipping point where I can say that I will keep working
on it until it's done.
Some info: https://github.com/notro/tinydrm/wiki

Thanks,
Noralf.

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[PATCH] fbtft: limit transfer length by spi device limit

[Michal Suchanek]

Some SPI controllers can transfer only small piece of data at a time.
Since SPI core gained a function to get the maximum transfer length use
it.

Signed-off-by: Michal Suchanek 
---

 Tested on sunxi spi with DMA enabled and disabled. Makes a visible speed
difference and display works in either case.

 drivers/staging/fbtft/fbtft-core.c | 9 +
 1 file changed, 9 insertions(+)

diff --git a/drivers/staging/fbtft/fbtft-core.c 
b/drivers/staging/fbtft/fbtft-core.c
index 0c1a77c..f3bdc8f 100644
--- a/drivers/staging/fbtft/fbtft-core.c
+++ b/drivers/staging/fbtft/fbtft-core.c
@@ -1346,6 +1346,15 @@ int fbtft_probe_common(struct fbtft_display *display,
return PTR_ERR(pdata);
}
 
+   if (sdev && (spi_max_transfer_size(sdev) < SIZE_MAX))
+   if ((pdata->txbuflen <= 0) || (pdata->txbuflen > 
spi_max_transfer_size(sdev))) {
+   dev_warn(dev,
+"Limiting used buffer size %i -> %i due to 
device %s transfer size limitation",
+pdata->txbuflen, spi_max_transfer_size(sdev),
+dev_name(>dev));
+   pdata->txbuflen = spi_max_transfer_size(sdev);
+   }
+
info = fbtft_framebuffer_alloc(display, dev, pdata);
if (!info)
return -ENOMEM;
-- 
2.8.1

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