linux-kernel - Re: [PATCH] spi: Increase imx51 ecspi burst length based on transfer length

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Message-ID: <20230916235334.fqqpowhvacg3xzqy@mercury.elektranox.org>
Date:   Sun, 17 Sep 2023 01:53:34 +0200
From:   Sebastian Reichel <sre@...nel.org>
To:     Stefan Moring <stefan.moring@...hnolution.nl>
Cc:     broonie@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de,
        festevam@...il.com, linux-imx@....com, linux-spi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] spi: Increase imx51 ecspi burst length based on transfer
 length

Hi,

On Fri, Sep 15, 2023 at 07:55:23AM +0200, Stefan Moring wrote:
> Op vr 15 sep 2023 om 00:47 schreef Sebastian Reichel <sre@...nel.org>:
> > On Wed, Jun 28, 2023 at 02:54:06PM +0200, Stefan Moring wrote:
> > > IMX51 supports 4096 bit burst lengths. Using the spi transfer length
> > > instead of bits_per_word increases performance significantly.
> > >
> > > Signed-off-by: Stefan Moring <stefan.moring@...hnolution.nl>
> > > ---
> >
> > I have an i.MX6ULL system with "inanbo,t28cp45tn89-v17" panel, which
> > breaks due to this change. Reverting this patch results in working
> > panel. Note, that the panel driver [0] does 'spi->bits_per_word = 9;'.
> >
> > [0] drivers/gpu/drm/panel/panel-sitronix-st7789v.c
>
> Would changing line 665 to ctrl |= (spi_imx->count * spi_imx->bits_per_word
> - 1) fix the issue?

--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -662,7 +662,7 @@ static int mx51_ecspi_prepare_transfer(struct spi_imx_data *spi_imx,
                if (spi_imx->count >= 512)
                        ctrl |= 0xFFF << MX51_ECSPI_CTRL_BL_OFFSET;
                else
-                       ctrl |= (spi_imx->count*8 - 1)
+                       ctrl |= (spi_imx->count*spi_imx->bits_per_word - 1)
                                << MX51_ECSPI_CTRL_BL_OFFSET;
        }

on top of 6.6-rc1 fixes the problem. Will you send a proper patch with

Reported-by: Sebastian Reichel <sre@...nel.org>
Fixes: 15a6af94a277 ("spi: Increase imx51 ecspi burst length based on transfer length")

or should I do it?

Greetings,

-- Sebastian

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