From: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org, Jyri Sarha <jyri.sarha@iki.fi>
Subject: Re: [PATCH 12/21] drm/tilcdc: Allow build without __iowmb()
Date: Wed, 10 Apr 2024 18:47:13 +0300 [thread overview]
Message-ID: <dedf46a9-640a-4ac4-b992-1bde76307ad2@ideasonboard.com> (raw)
In-Reply-To: <ZhavXcFrgzw5UApH@intel.com>
On 10/04/2024 18:25, Ville Syrjälä wrote:
> On Wed, Apr 10, 2024 at 12:06:29PM +0300, Tomi Valkeinen wrote:
>> On 08/04/2024 20:04, Ville Syrjala wrote:
>>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>>
>>> __iowmb() isn't available on most architectures. Make
>>> its use optional so that the driver can be built on
>>> other architectures with COMPILE_TEST=y.
>>>
>>> Cc: Jyri Sarha <jyri.sarha@iki.fi>
>>> Cc: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
>>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> ---
>>> drivers/gpu/drm/tilcdc/tilcdc_regs.h | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_regs.h b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
>>> index f90e2dc3457c..44e4ada30fba 100644
>>> --- a/drivers/gpu/drm/tilcdc/tilcdc_regs.h
>>> +++ b/drivers/gpu/drm/tilcdc/tilcdc_regs.h
>>> @@ -125,7 +125,9 @@ static inline void tilcdc_write64(struct drm_device *dev, u32 reg, u64 data)
>>> #if defined(iowrite64) && !defined(iowrite64_is_nonatomic)
>>> iowrite64(data, addr);
>>> #else
>>> +#ifdef __iowmb
>>> __iowmb();
>>> +#endif
>>> /* This compiles to strd (=64-bit write) on ARM7 */
>>> *(volatile u64 __force *)addr = __cpu_to_le64(data);
>>> #endif
>>
>> As the memory barrier is an important part there, would it be better to
>> ifdef based on COMPILE_TEST, to make it clear why it's being done?
>
> I can do that if you prefer.
>
> I suppose the real question is why iowrite64() doesn't work
> if a hand rolled version does work?
If I recall right, there is (was?) no iowrite64. The bus is 32 bit
anyway. But the two 32 bit registers written with the tilcdc_write64()
have an annoying HW race, so we tried to find a method of writing them
that reduces the chance of race to a minimum.
Tomi
next prev parent reply other threads:[~2024-04-10 15:47 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-08 17:04 [PATCH 00/21] drm: Increase COMPILE_TEST=y coverage Ville Syrjala
2024-04-08 17:04 ` [PATCH 01/21] drm/armada: Fix printk arguments Ville Syrjala
2024-04-08 17:04 ` [PATCH 02/21] drm/armada: Fix armada_debugfs_crtc_reg_write() return type Ville Syrjala
2024-04-08 17:04 ` [PATCH 03/21] drm/armada: Allow build with COMPILE_TEST=y Ville Syrjala
2024-04-08 17:04 ` [PATCH 04/21] drm/imx/dcss: Fix 64bit divisions Ville Syrjala
2024-04-08 17:04 ` [PATCH 05/21] drm/imx/dcss: Allow build with COMPILE_TEST=y Ville Syrjala
2024-04-08 17:04 ` [PATCH 06/21] drm/sti: Include linux/io.h for devm_ioremap() Ville Syrjala
2024-05-27 15:28 ` Alain Volmat
2024-04-08 17:04 ` [PATCH 07/21] drm/sti: Allow build with COMPILE_TEST=y Ville Syrjala
2024-05-27 15:29 ` Alain Volmat
2024-05-28 19:45 ` Ville Syrjälä
2024-04-08 17:04 ` [PATCH 08/21] drm/hisilicon/kirin: Include linux/io.h for readl()/writel() Ville Syrjala
2024-04-08 17:08 ` John Stultz
2024-04-08 17:04 ` [PATCH 09/21] drm/hisilicon/kirin: Fix 64bit divisions Ville Syrjala
2024-04-08 17:09 ` John Stultz
2024-04-08 17:04 ` [PATCH 10/21] drm/hisilicon/kirin: Fix MASK(32) on 32bit architectures Ville Syrjala
2024-04-08 17:09 ` John Stultz
2024-04-08 17:04 ` [PATCH 11/21] drm/hisilicon/kirin: Allow build with COMPILE_TEST=y Ville Syrjala
2024-04-08 17:11 ` John Stultz
2024-04-08 17:04 ` [PATCH 12/21] drm/tilcdc: Allow build without __iowmb() Ville Syrjala
2024-04-10 9:06 ` Tomi Valkeinen
2024-04-10 15:25 ` Ville Syrjälä
2024-04-10 15:47 ` Tomi Valkeinen [this message]
2024-04-10 17:04 ` Ville Syrjälä
2024-04-10 17:12 ` Tomi Valkeinen
2024-04-11 13:40 ` jyri.sarha
2024-04-08 17:04 ` [PATCH 13/21] drm/tilcdc: Allow build with COMPILE_TEST=y Ville Syrjala
2024-04-10 9:06 ` Tomi Valkeinen
2024-04-08 17:04 ` [PATCH 14/21] drm/omap: Open code phys_to_page() Ville Syrjala
2024-04-10 9:14 ` Tomi Valkeinen
2024-04-08 17:04 ` [PATCH 15/21] drm/omap: Allow build with COMPILE_TEST=y Ville Syrjala
2024-04-08 17:12 ` Ville Syrjälä
2024-04-10 9:15 ` Tomi Valkeinen
2024-04-08 17:04 ` [PATCH 16/21] drm/atmel-hlcdc: " Ville Syrjala
2024-04-09 16:55 ` Sam Ravnborg
2024-04-08 17:04 ` [PATCH 17/21] drm/fsl-dcu: " Ville Syrjala
2024-04-08 17:04 ` [PATCH 18/21] drm/mediatek: " Ville Syrjala
2024-04-08 17:04 ` [PATCH 19/21] drm/meson: " Ville Syrjala
2024-04-08 17:23 ` Martin Blumenstingl
2024-04-08 17:04 ` [PATCH 20/21] drm/rcar-du: " Ville Syrjala
2024-04-09 7:26 ` Geert Uytterhoeven
2024-04-10 22:36 ` Laurent Pinchart
2024-04-08 17:04 ` [PATCH 21/21] drm/stm: " Ville Syrjala
2024-04-10 12:15 ` Raphael Gallais-Pou
2024-04-10 6:07 ` [PATCH 12/21] drm/tilcdc: Allow build without __iowmb() sarha
2024-04-10 6:07 ` [PATCH 13/21] drm/tilcdc: Allow build with COMPILE_TEST=y sarha
2024-05-08 19:40 ` [PATCH 00/21] drm: Increase COMPILE_TEST=y coverage Ville Syrjälä
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